The present application is a continuation-in-part of co-pending application Ser. No. 08/084,267 “Transdermal Perfusion of Fluids” filed 7 Jan. 1992 pursuant to International application PCT/EP92/00029. The contents of this co-pending application are incorporated by reference into the present application.[0001]
This invention relates to transdermal perfusion of fluids through the skin of the human or animal body and in particular but not exclusively to apparatus for de-epithelialising the skin by the suction blister method to enable perfusion to take place directly via the dermis layer. Aspects of the invention also relate to perfusion of body fluids through the skin for external collection and sampling.[0002]
The transdermal perfusion of fluids for drug delivery has in recent years become an increasingly favoured alternative to intravenous or oral drug delivery. The technique has however found limited application because the epidermis (outer skin layer) forms an effective barrier to the perfusion of substances and in particular drugs having a large molecular size.[0003]
In its simplest form, transdermal absorption has been achieved using skin patches in which a substance in a fluid contacting the skin is absorbed by diffusion whereby the random molecular motion tends to equilibrate the concentration of the substance across the membrane provided by the skin.[0004]
Various techniques have been proposed to enhance transdermal delivery including iontophoresis and the use of chemical enhancers. (Chemical enhancement is for example described in Int. J. Pharm. 1989, 49, 199-201 and Iontophoresis in J. Pharm. Sci. 1990, 79, 490-93). Mechanical stimulation for instance by ultrasound has also been used to enhance transdermal delivery. (Use of ultrasound is for example described in Pharm. Res. 1992, 9, 559-564). There remains a need however to provide a more effective transdermal technique particularly for peptides and hormones which hitherto have not been capable of being transdermally administered.[0005]
It is also known from U.S. Pat. No. 3,486,504 to provide a resilient housing with an air release valve which can be held against an infected skin area by suction. A medicated and absorbent dressing within the housing is thereby held in contact with the skin.[0006]
It is also known in the field of skin grafting to remove portions of the epidermis to expose the dermis layer of skin by the application of suction in which a partial vacuum of about 200 mm of mercury applied for a period of two or three hours has the effect of delaminating the epidermis from the dermis to form a blister containing a clear blister fluid. (A suction blister method is for example described by Kiistala U, “The suction blister method for the in vivo separation of epidermis from dermis in human skin”, Thesis, Univ of Helsinki, 1976). Such blisters have a roof which comprises the epidermis and can easily be removed for skin grafting.[0007]
According to one aspect of the present invention there is disclosed apparatus for use in transdermal administration of fluids through the skin of a human or animal body, the apparatus comprising a housing attachable to the body, the housing having a contact surface which in use is held in contact with a portion of skin by an adhesive layer, the housing defining a chamber and the contact surface defining an aperture communicating with the chamber, the apparatus further comprising suction means operable during a preparatory phase of operation of the apparatus to apply suction to the skin at a treatment site which is accessible via the aperture such that an area of the skin's epidermis at the treatment site is detached from the skin's underlying dermis, means for disrupting the detached area of epidermis such that the dermis is exposed within the chamber, and fluid supply means operable during a perfusion phase of operation of the apparatus to supply fluid to the chamber such that fluid in the chamber may be absorbed by the dermis without intervention of the epidermis.[0008]
The process of removing a portion of epidermis, also referred to as an epithelial layer, from the underlying intact dermis is referred to herein as a de-epithelialising method and the resulting area of skin from which the epidermis has been removed will be referred to as a de-epithelialised erosion or lesion. Such an erosion formed by splitting the epidermis from the dermis by suctioning followed by disruption of the detached epidermis allows a unique form of access to the body. The suctioning process causes a spit to occur reproducibly through the lamina lucida part of the basal membrane between the epidermis and the dermis. Although the thickness of the epidermis varies over different parts of the body, the epidermis over most areas is so delicate and thin as to be transparent. Irrespective of the thickness of the epidermis however, the split occurs at the basal lamina level. The dermis may vary in thickness also but this variation similarly does not affect the level at which the split occurs.[0009]
The portion of epidermis which is removed in such a method is devoid of vessels and nerves. The underlying connective tissue of the lamina densa with scattered islands of epithelial adnexae is left behind. The lamina densa is a robust fibrous layer which is open to molecular passage but structurally remains a safeguard to the underlying dermis which remains structurally completely intact.[0010]
The blood flow in the exposed dermis is strongly increased for several days following formation of such an erosion allowing increased macro molecular passage, the lymphatic system of the dermis remaining intact and the lymph vessels allowing free passage of even the largest plasma proteins.[0011]
The split is formed after exposing the skin surface to a pressure of 200 millimetres of mercury below atmospheric pressure for a period of two to two and a half hours. This period may be reduced to less than one hour by local heating.[0012]
During the latter part of the suctioning period, the split fills with clear liquid emanating from the underlying microvessels, finally forming a fluid filled generally semi-spherical blister covered externally by the detached layer of epidermis.[0013]
This detached layer of epidermis must be disrupted by being burst, broken or removed in order to provide access for drug absorption or sampling. The exposed dermis will readily absorb fluid substances brought into contact with the dermis at the erosion, the active ingredients of such substances typically being transdermally absorbed by diffusion through the dermis in response to a concentration gradient of the active ingredient existing across the thickness of the dermis, and the substances being rapidly dispersed through the body via the blood vessels of the dermis. A clear fluid exudate continues to form at the erosion by passing outwardly through the dermis. This exudate typically can be analysed to monitor levels of natural or artificial substances in the body. A variety of transdermal perfusion procedures involving the passage of substances through the exposed dermis are thereby envisaged. The term perfusion in the present context is used to encompass such diffusion either into or from the body in either a natural or enhanced manner.[0014]
One aspect of the present invention relates to an improved apparatus which can be safely and reliably operated in a simple manner such that in many instances patients themselves may be left to carry out the stages of operation required to complete the procedure.[0015]
According to a further aspect of the present invention there is disclosed apparatus for use in transdermal perfusion procedures comprising a housing, securing means operable to secure a contact surface of the housing in sealing contact with an area of skin in use, an aperture defined in the contact surface and communicating with an access port defined by the housing, a suction cup located in the access port and having a lip portion extending peripherally of the aperture, the suction cup defining an outlet port and a suction chamber communicating with both the outlet port and the aperture, the apparatus further comprising suction means operable to apply suction to the suction chamber in the outlet port and cutting means operable to sever from the lip portion a removable portion of the suction cup defining the outlet port.[0016]
An advantage of such apparatus is that a suction blister formed within the suction chamber can be safely cut at the same time or the removable portion is severed in a controlled manner by operation of the cutting means and such that a roof of the blister may be disposed of by subsequent removal of the removable portion of the suction cup. The roof of the blister is constituted by an area of epidermis of the skin detached by the formation of the suction blister from the underlying dermis so that following removal of the roof of the blister a small skin erosion is formed providing direct access to the intact dermis for a transdermal perfusion procedure which may involve placing a fluid in contact with the dermis for absorption into the body or may alternatively involve the collection and sampling of exudate emanating from the erosion.[0017]
Preferably the apparatus further comprises an actuator mounted on the housing and the cutting means comprises a blade which is movable to sever the removable portion in response to movement of the actuator relative to the housing.[0018]
The blade may thereby be safely moved in a controlled manner.[0019]
Preferably the suction means defines an expansion chamber communicating with the outlet port via a tube, the suction means being operable to expand the volume of the expansion chamber from an initial volume to an expanded volume and further comprising locking means operable to maintain the expansion chamber in its expanded volume.[0020]
Suction within the suction chamber may thereby be applied over a prolonged period by operation of the locking means to maintain the expansion chamber in its expanded condition.[0021]
Advantageously the suction means comprises a syringe.[0022]
Advantageously the apparatus further comprises an indicator responsive to displacement of air along the tube and operable to provide an indication of volumetric displacement of air from the suction chamber in response to the formation of a suction blister within the suction chamber.[0023]
An advantage of such an indicator is to allow the formation of the suction blister to be remotely monitored. This is important since the time taken for the formation of a suction blister of a given size will vary from patient to patient and will vary according to other prevailing operating conditions such as temperature. Visual inspection of the suction blister will not generally be a convenient option.[0024]
Conveniently the indicator comprises a slug of liquid contained within the tube and indicating means for indicating the extent of linear displacement of the slug of liquid through the tube.[0025]
Conveniently the indicator comprises a clamp securable at an adjustable position along the tube and wherein the indicating means is supported by the clamp.[0026]
Preferably the suction means comprises a connector which is releasably engagable with the outlet port whereby disengagement of the connector from the outlet port admits ambient air to the suction chamber.[0027]
An advantage of such a connector is to allow the suction means to be dissociated from the housing and discarded by the patient after the formation of the suction blister.[0028]
Preferably the apparatus comprises an arming device operable to prevent actuation of the cutting means until the connector has been disconnected from the outlet port.[0029]
An advantage of such an arming device is to ensure that the application of suction within the suction chamber is discontinued prior to actuation of the cutting means.[0030]
This is a safety feature which avoids the possibility of damaging the underlying dermis. Without this safety feature, there would be the possibility that suction within the suction chamber could deform the dermis into a bulbous projection extending into the suction chamber to an extent such that it could be cut by the blade during the blister cutting operation.[0031]
Conveniently the arming device comprises an arming pin insertable into the housing to a location in which it prevents relative movement of the actuator and housing, the arming device further comprising a handle connected to both the connector and the arming pin.[0032]
Preferably the housing comprises a base defining the contact surface and a rotatable portion in which the access port is defined at an eccentric location relative to the rotation axis of the rotatable portion.[0033]
The rotatable portion may then comprise a reservoir having an outlet located eccentrically relative to the rotational axis such that, after the removable portion has been removed, the outlet is locatable by rotation of the rotatable portion in registration with the aperture defined in the base.[0034]
Advantageously a continuous seal extends peripherally of the outlet and is operable between the rotatable portion and the base.[0035]
The seal thereby allows the contents of the reservoir to be sealed against loss of contents and ingress of air during an initial period in which the outlet is overlaid by a continuous surface of the base. Subsequently the seal provides sealing action peripherally of the aperture defined in the base when the outlet is in registration with the aperture, loss of fluid thereby being prevented together with the prevention of ingress of contaminants.[0036]
Advantageously the apparatus further comprises a second continuous seal peripheral to a surface portion of the rotatable portion at a location which is eccentric relative to the rotational axis such that the surface portion is movable by rotation of the rotatable portion into registration with the aperture.[0037]
The surface portion of the rotatable portion may thereby be used to form a closure to the suction chamber after use of the apparatus to deliver the contents of the reservoir to the dermis, in this final position the second continuous seal being operable to form an airtight seal between the surface portion and the base against the ingress of contaminants.[0038]
Conveniently the continuous seal and the second continuous seal are integrally formed.[0039]
Advantageously the suction cup comprises a cylindrical portion intermediate the lip and the outlet port and having a cylindrical axis substantially orthogonal to the contact surface and the cutting means is operable to sever the cylindrical portion at a predetermined location spaced from the lip portion.[0040]
Preferably the suction cup comprises an internal surface which is adhesively coated.[0041]
A suction blister will therefore tend to adhere to the internal surfaces of the suction cup thereby avoiding the collapse of the blister before cutting in the event of the blister becoming accidentally ruptured.[0042]
The rotatable portion may define a sampling port at an eccentric location relative to the rotation axis of the rotatable portion, the apparatus further comprising a sampling piston reciprocatable in the sampling port to vary the volume of a sampling chamber defined therein whereby suction may be created in the sampling chamber, the sampling port being locatable, after the removable portion has been removed, by rotation of the rotatable portion in registration with the aperture defined in the base such that the aperture communicates with the sampling chamber.[0043]
Exudate emanating from the exposed dermis may thereby be sampled via the sampling port without removal of the housing from the skin to which it is attached. On completion of sampling, the rotatable portion may then be rotated into a position in which the delivery of a drug commences or recommences, or alternatively may be rotated into a position in which the erosion is occluded.[0044]
The ability of the sampling piston to create suction in the sampling chamber may be utilised to enhance the rate at which exudate is collected from the erosion by increasing the rate of production of exudate in response to a pressure differential applied across the dermis.[0045]
Conveniently the sampling piston defines a bore to receive an outflow of fluid from the sampling chamber, the apparatus further comprising an openable closure operable to close the bore to maintain suction in the sampling chamber.[0046]
Access to the exudate fluid in the sampling chamber may thereby be gained by opening the closure as required.[0047]
Conveniently the apparatus further comprises a sampling device connected to the sampling piston and defining a sampling channel communicating in use with the bore to receive a sample of fluid from the sampling chamber.[0048]
Advantageously the sampling piston is reciprocatable in the sampling port by means of co-operable screw threaded formations of the sampling piston and the rotatable portion.[0049]
According to a further aspect of the present invention there is disclosed a syringe for creating suction to be applied to the suction blister forming apparatus, the syringe comprising a cylinder within which a piston is movable to define an expansion chamber of variable volume, the piston comprising an actuating handle projecting from the cylinder and a locking arm formed integrally therewith, the locking arm being resiliently biased for movement into a locking position in which a free end of the locking arm engages a co-operating locking formation of the cylinder when the piston is in a retracted position to create and maintain suction in the expansion chamber.[0050]
Such a syringe may be conveniently locked for a prolonged period with the piston in the retracted position to thereby maintain suction during the formation of a suction blister.[0051]
According to a further aspect of the present invention there is disclosed apparatus for use in transdermal perfusion procedures comprising a suction cup for use in applying suction to an area of skin, a tube communicating with the suction cup and connectable in use to a suction means, and an indicator responsive to displacement of air along the tube and operable to provide an indication of volumetric displacement of air from the suction cup in response to the formation of a suction blister or the ingress of body fluid within the suction cup during a period in which suction is maintained within the suction cup.[0052]
Such an indicator overcomes the problem of determining whether a suction blister has sufficiently formed before initiating the next stage of removing or disrupting the blister roof to expose the dermis. Such an indicator provides a convenient means of measuring volumetric growth of a suction blister without requiring contact with the blister and avoiding the need to incorporate any sensor or measurement device in the immediate proximity of the blister. The indicator will typically be located several centimetres clear of the suction cup.[0053]
Similarly, when used in the collection of exudate at an erosion, the indicator allows the collected volume of exudate to be readily observed.[0054]
Preferably the indicator comprises a slug of liquid located in a transparent portion of the tube and indicating means for indicating the extent of linear displacement of the slug of liquid through the tube.[0055]
Displacement of the slug of liquid may be observed visually relative to a scale clamped to the tube or may be monitored by an electro-optic sensor.[0056]
Preferably the apparatus comprises a liquid storage structure connected to the tube and defining a liquid storage chamber communicating with the transparent portion of the tube and means for displacing a quantity of liquid from the liquid storage chamber into the tube to thereby constitute the slug of liquid.[0057]
An advantage of such an arrangement is that it avoids the need for the slug of liquid to be held within the tube prior to use, thereby overcoming the potential problem of disruption of the slug of liquid by handling prior to use.[0058]
According to a further aspect of the present invention there is disclosed apparatus for use in transdermal perfusion procedures, comprising a housing, securing means operable to secure a contact surface of the housing in sealing contact with an area of skin in use, an aperture defined in the contact surface, the housing comprising a base defining the contact surface and a rotatable portion in which an access port is defined at an eccentric location relative to the rotation axis of the rotatable portion and whereby in an initial position of the rotatable portion the access port is aligned in registration with the aperture to facilitate formation of a de-epithelialised skin erosion within the aperture, the rotatable portion further comprising a plurality of openings defined at eccentric locations relative to the rotation axis of the rotatable portion whereby successive openings may be brought into registration with the aperture by rotation of the rotatable portion and a plurality of compartments within the rotatable portion which are accessible via the respective openings.[0059]
Two or more of the compartments may comprise reservoirs containing respective fluids whereby the respective fluids may be separately and sequentially communicated to the aperture via respective openings by successive rotational steps of the rotatable portion.[0060]
One or more of the compartments may contain means for sampling body fluids communicated to the compartment from the aperture via the respective opening.[0061]
Advantageously the apparatus comprises an actuating mechanism operable to facilitate rotational movement of the rotatable portion relative to the base in response to movement of an actuating member of the mechanism.[0062]
The mechanism may comprise a geared pinion mounted on the base for rotation by movement of the actuator and a circumferential rack mounted on the rotatable portion and engaged by the pinion.[0063]
According to a further aspect of the present invention there is disclosed apparatus for use in transdermal perfusion procedures, comprising a housing, securing means operable to secure a contact surface of the housing in sealing contact with an area of skin in use, an aperture defined in the contact surface and communicating with an access port defined by the housing, means for applying suction to the aperture via the access port and heating means operable to apply heat to a heated portion of the contact surface peripheral to the aperture.[0064]
When the housing is secured to an area of skin to form a suction blister, the application of heat reduces the time taken for a suction blister to form. When applied to an area of skin in which a de-epithelialised erosion exists for the purpose of sampling exudate, the application of heat enhances the rate at which exudate may be collected.[0065]
The heating means may comprise a resistive heating element and a power circuit operable to pass electrical current through the heating element.[0066]
According to a further aspect of the present invention there is disclosed apparatus for use in transdermal perfusion procedures, comprising a housing, securing means operable to secure a contact surface of the housing in sealing contact with an area of skin in use, an aperture defined in the contact surface, the surface comprising a base defining the contact surface and a moveable portion in which an access port is defined, the moveable portion being moveable between an initial position in which the access port is aligned in registration with the aperture to facilitate formation of a de-epithelialised skin erosion within the aperture and a second in position in which an opening defined by the moveable portion is located in registration with the aperture, and further comprising a pump operable to transfer liquid between the aperture and the compartment via the opening.[0067]
According to a further aspect of the present invention there is disclosed apparatus for use in transdermal perfusion procedures, comprising a housing, securing means operable to secure a contact surface of the housing in sealing contact with an area of skin in use, an aperture defined in the contact surface whereby a de-epithelialised skin erosion may be formed in use via the aperture, the housing defining an enclosure communicating with the aperture and a syringe connected to the enclosure for the delivery of liquid thereto, wherein the syringe comprises a piston and cylinder and screw-threaded actuating means for advancing the piston in metered stages by rotation of the actuator relative to the cylinder to thereby dispense metered doses of liquid.[0068]
This provides a convenient means of delivering metered quantities of liquid for transdermal absorption at a de-epithelialised skin erosion.[0069]
According to a further aspect of the present invention there is disclosed apparatus for use in transdermal perfusion procedures, comprising a housing, securing means operable to secure a contact surface of the housing in sealing contact with an area of skin in use, an aperture defined in the contact surface, the housing comprising a base defining the contact surface and a moveable portion in which an access port is defined and whereby in an initial position of the moveable portion the access port is aligned in registration with the aperture to facilitate formation of a de-epithelialised skin erosion within the aperture, the moveable portion further comprising an opening which may be brought into registration with the aperture in a second position of the moveable portion thereby providing communication between a chamber of the moveable portion and the aperture, the apparatus further comprising a transdermal skin patch accommodated within the chamber and a patch applicator operable in use to deploy the patch from the chamber through the aperture into engagement with the skin erosion.[0070]
An advantage of such apparatus is that a patch may be applied to the skin erosion without being handled by the user and without exposing the de-epithelialised skin erosion.[0071]
According to a further aspect of the present invention there is disclosed a method of administering a substance by transdermal delivery, comprising the steps of preparing first and second de-epithelialised skin erosions at separate skin sites, applying first and second enclosures respectively over the first and second erosions to define a sampling cell and a drug delivery cell respectively, extracting exudate from the sampling cell by means of a first pump to a bio-sensor, operating the bio-sensor to produce an output signal representative of a measurable property of the exudate, delivering metered quantities of a liquid containing the substance to the drug delivery cell by operation of a second pump, controlling the rate of delivery of the second pump by operation of a control unit responsive to the output of the bio-sensor.[0072]
According to a further aspect of the present invention there is disclosed a method of controlled release of a substance for transdermal absorption, comprising the steps of absorbing quantities of the substance into porous polymeric particles, mixing the particles with granules of permanent magnetic material encapsulated in a polymeric material, placing the resulting mixture in a cell defined by an enclosure, applying an alternating magnetic field within the cell, thereby inducing mechanical vibration in the mixture to release the substance from the particles.[0073]
According to a further aspect of the present invention there is disclosed a method of controlled release of a substance for transdermal absorption, comprising the steps of mixing a liquid containing the substance with a quantity of a hydrogel, placing the resulting mixture within a cell defined an enclosure and heating the contents of the cell by operation of a heating means to thereby dissociate liquid from the hydrogel so as to be released from the cell.[0074]
According to a further aspect of the present invention there is disclosed apparatus for use in transdermal perfusion procedures, comprising a housing, securing means operable to secure a contact surface of the housing in sealing contact with an area of skin in use, an aperture defined in the contact surface, the housing comprising a base defining the contact surface and a movable portion in which an access port is defined and whereby in an initial position of the movable portion the access port is aligned in registration with the aperture to facilitate formation of a de-epithelialised skin erosion within the aperture, the movable portion further comprising an opening which may be brought into registration with the aperture in a second position of the movable portion, the apparatus further comprising an implementing device operable in use to implement a transdermal procedure at the skin erosion via the opening and releasable connecting means operable between the movable portion and the implementing device.[0075]
An advantage of such apparatus is to allow a succession of different implementing devices to be connected, thereby allowing a sequence of different procedures to be performed or to allow procedures to be repeated with fresh implementing devices.[0076]
Preferably the implementing device comprises a reservoir defining a fluid receiving chamber and an outlet communicating with the opening of the movable portion when the implementing device is operatively connected therewith.[0077]
Successive implementing devices may thereby be connected in turn. In this way a succession of different drugs or drug concentrations may be administered.[0078]
Conveniently the implementing device comprises suction means connected to the opening when the implementing device is operatively connected therewith and operable to create suction to thereby draw fluid from the fluid receiving chamber into the opening.[0079]
The operation of the suction means enables the liquid contained in a reservoir to displace air from the opening and fluid into contact with the de-epithelialised skin erosion. When replacing one implementing device with a further device, operation of the suction means in the further implementing device will also serve to evacuate from the opening any residual liquid remaining from the application of the previous implementing device.[0080]
According to a further aspect of the present invention there is disclosed a method of transdermally sampling body fluid from the human or animal body comprising the steps of:[0081]
removing an epithelial layer from a portion of skin at a skin site;[0082]
securing an enclosure defining a sampling chamber to the body such that a contact surface of the enclosure is maintained in sealing contact with an area of skin peripheral to the skin site;[0083]
operating a suction means connected to the enclosure to apply suction within the sampling chamber during a period in which transdermally exuded body fluid is collected in the sampling chamber;[0084]
discontinuing the application of suction, and sampling fluid from the sampling chamber via an operable closure of the enclosure.[0085]
Such a method provides an improved, minimally invasive procedure for sampling from the body. Removal of the epithelial layer from the portion of skin exposes an area of dermis at an erosion formed at the skin site. As described above, in the absence of applied suction to the exposed dermis, exudate will be produced gradually at the erosion. The application of suction enhances the rate of production of exudate. The effect of suction is to reduce the air pressure external to the dermis thereby creating a pressure differential across the dermis resulting in convective flow of plasma through the dermis. The dermis acts as a porous capillary membrane which acts as a sieve preventing the loss of blood cells but permitting relatively large molecules such as molecules of sugar and insulin to be carried in the exuded plasma. The rate at which fluid is exuded is thereby increased above the rate associated with normal diffusion of plasma through the dermis in the absence of suction. The time taken for plasma to pass through the dermis is reduced thereby decreasing the risk of significant reactions taking place in the plasma during this transition.[0086]
An advantage of using this method is that a fresh sample of exudate may be drawn from the erosion within a relatively short time period of the order of five minutes for example, in sufficient quantity for an analysis to be carried out. Typically small volumes of fluid are required for modern analysis techniques including chemiluminescence and fluorescence for example.[0087]
The method is preferable over known techniques of invasive sampling, such as the use of a hypodermic needle, where typically unnecessarily large volumes are sampled and the resulting wound which penetrates the dermis may create difficulties such as those of thrombosis in vessels where sampling is frequently conducted.[0088]
The method of the present invention also has particular advantage in taking samples from paediatric patients and premature babies where vessels for cannulation are difficult to find and where it is undesirable to withdraw significant volumes for sampling due to risk associated with blood loss.[0089]
According to the present invention there is further disclosed apparatus for use in sampling exudate from a de-epithelialised skin erosion, the apparatus comprising an enclosure defining a sampling chamber, securing means operable to sealingly secure a contact surface of the enclosure to an area of skin peripheral to the erosion in use, an aperture being defined in the contact surface and communicating with the sampling chamber, an outlet communicating with the sampling chamber for the outflow of exudate, an openable closure for the outlet, and means for applying suction within the sampling chamber to enhance the rate at which exudate is produced.[0090]
Conveniently the means for applying suction comprises a piston reciprocatably mounted in the sampling chamber whereby the volume of the sampling chamber is variable.[0091]
Preferably the chamber is cylindrical and receives the piston as a sliding fit therein.[0092]
Advantageously the piston defines a capillary bore extending through the piston and communicating between the chamber and the outlet.[0093]
The openable closure may comprise a cap releasably attachable to the piston.[0094]
The apparatus may further comprise a sampling device releasably connectable to the piston and defining a sampling channel communicating with the bore to receive in use a sample of exudate from the chamber.[0095]
The sampling device may be a transparent cuvette defining a capillary slot constituting the sampling channel and operable to sample exudate from the outlet by capillary action.[0096]
The means for applying suction may alternatively comprise a syringe connected to an air of actuation port defined by the enclosure.[0097]
The outlet may then be formed in a tubular side wall of the enclosure, the outlet being overlaid by a resilient sleeve constituting the openable closure.[0098]
Preferred embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings of which[0099]
FIG. 1 is a sectioned elevation of a first apparatus for forming a suction blister;[0100]
FIG. 2 is a sectioned elevation of a second apparatus for forming a suction blister and having an actuator pin;[0101]
FIG. 3 is a sectioned elevation of the apparatus of FIG. 2 showing the actuator pin in an advanced position in readiness to disrupt a suction blister;[0102]
FIG. 4 is a sectioned elevation of the apparatus of FIGS. 2 and 3 showing the actuator pin in a further advanced position in which the blister is disrupted to expose the dermis;[0103]
FIG. 5 is a sectioned elevation of a third apparatus for forming a suction blister and having a pull ring actuator;[0104]
FIG. 6 is a sectioned elevation of a fourth apparatus for forming a suction blister and having laterally disposed actuator pins;[0105]
FIG. 7 is a sectioned elevation of a fifth apparatus for forming a suction blister and comprising a sprung bellows shown in a compressed state;[0106]
FIG. 8 is a sectioned elevation of the apparatus of FIG. 7 showing the sprung bellows in an expanded state;[0107]
FIG. 9 is a sectioned elevation of a sixth apparatus for removing an area of epidermis by grinding;[0108]
FIG. 10 is a sectioned elevation of a seventh apparatus for use in transdermal perfusion of a drug;[0109]
FIG. 11 is a sectioned elevation of the apparatus of FIG. 10 showing removal of a de-epithelialisation component of the apparatus;[0110]
FIG. 12 is a sectioned elevation of the apparatus of FIGS. 10 and 11 in which the de-epithelialisation component is replaced by a drug delivery module;[0111]
FIG. 13 is a sectioned elevation of an alternative drug delivery module for use with the apparatus of FIGS.[0112]10 to12;
FIG. 14 is a sectioned elevation of an eighth apparatus for transdermal delivery of a drug including means for forming a suction blister, disrupting the blister and applying the drug directly to the exposed dermis;[0113]
FIG. 15 is a sectioned elevation of a ninth apparatus having a cannula for drug delivery by injection;[0114]
FIG. 16 is a sectioned elevation of the apparatus of FIG. 15 showing the cannula extending through the skin;[0115]
FIG. 17 is a perspective view of a tenth apparatus for transdermal delivery of a drug and showing a suction chamber in its pre-use configuration;[0116]
FIG. 18 is a perspective view of the apparatus of FIG. 17 showing the introduction via a cannula of partial vacuum within the suction chamber;[0117]
FIG. 19 is a perspective view of the apparatus of FIGS. 17 and 18 showing actuation of a blister disrupting fin;[0118]
FIG. 20 is a perspective view of the apparatus of FIGS.[0119]17 to19 showing the opening of a valve admitting drug to the chamber;
FIG. 21 is a sectioned elevation of an eleventh apparatus for transdermal drug delivery in its pre-use configuration;[0120]
FIG. 22 is a sectioned elevation of the apparatus of FIG. 21 showing the actuation of suction means to apply partial vacuum to the skin;[0121]
FIG. 23 is a sectioned elevation of the apparatus of FIGS. 21 and 22 showing the release of partial vacuum following formation of a skin blister;[0122]
FIG. 24 is a sectioned elevation of the apparatus of FIGS.[0123]21 to23 showing the disruption of the blister;
FIG. 25 is a plan view of the apparatus of FIGS.[0124]21 to24;
FIG. 26 is a side elevation of the apparatus of FIGS.[0125]21 to25;
FIG. 27 is a section showing detail of a drug injection port of the apparatus of FIGS.[0126]21 to26;
FIG. 28 is a section showing detail of a suction port valve of the apparatus of FIGS.[0127]21 to27;
FIG. 29 is a section showing detail of an alternative drug injection port for use with the apparatus of FIGS.[0128]21 to26;
FIG. 30 is a perspective view of the apparatus of FIGS.[0129]21 to28 showing attachment to an arm of a patient;
FIG. 31 is a perspective view of the apparatus of FIGS.[0130]21 to28 showing an alternative means of attachment to an arm of a patient;
FIG. 32 is a perspective view of the apparatus of FIGS.[0131]21 to28 showing a further alternative means of attachment to the arm of a patient; and
FIG. 33 is an elevation of the apparatus of FIG. 32;[0132]
FIG. 34 is a schematic sectional elevation of an alternative device showing the formation of a suction blister within a suction cup;[0133]
FIG. 35 is a schematic sectional elevation of the device of FIG. 34 after the suction cup and blister have been severed;[0134]
FIG. 36 is a sectioned elevation of the device of FIGS. 34 and 35 during a drug delivery phase of operation;[0135]
FIG. 37 is a sectional elevation of the device of FIGS.[0136]34 to36 shown after completion of the drug delivery phase;
FIG. 38 is a perspective view of the suction cup and arming device of the device of FIGS.[0137]34 to37;
FIG. 39 is a sectional elevation of the device of FIGS.[0138]34 to38 with the suction cup removed;
FIG. 40 is a plan view of a base of the device of FIGS.[0139]34 to39;
FIG. 41 is a sectional elevation of the base of FIG. 40;[0140]
FIG. 42 is a plan view of a rotatable portion of the device of FIGS.[0141]34 to39;
FIG. 43 is a sectional elevation of the rotatable portion of FIG. 42;[0142]
FIG. 44 is a plan view of a cover plate for the rotatable portion of FIGS. 42 and 43;[0143]
FIG. 45 is a sectional elevation of the cover plate of FIG. 44;[0144]
FIG. 46 is a plan view of an actuating ring of the device of FIGS.[0145]34 to39;
FIG. 47 is a sectional elevation of the actuating ring of FIG. 46;[0146]
FIG. 48 is a plan view of the device of FIGS.[0147]34 to39 with the suction cup omitted and showing the device in a rest position prior to removal of the arming device;
FIG. 49 is a plan view of the arrangement of FIG. 48 with the arming device removed;[0148]
FIG. 50 is a plan view of the arrangement of FIG. 48 after rotation of the actuating ring to a position in which the blade is moved through the access port in which the suction cup is locatable;[0149]
FIG. 51 is a plan view of the arrangement of FIG. 48 showing a further position in which the rotatable portion has been rotated to bring an outlet port of the reservoir into registration with the access port;[0150]
FIG. 52 is a plan view of the arrangement of FIG. 48 following further movement of the rotatable portion to a position in which the access port is sealed;[0151]
FIG. 53 is a plan view of the interior of a modified rotatable portion;[0152]
FIG. 54 is a plan view of an alternative device having a rotatable key for rotating the rotatable portion;[0153]
FIG. 55 is a schematic sectioned elevation of an alternative device having a skin heating element;[0154]
FIG. 56 is a schematic sectioned elevation of a further alternative device having a brush for removing debris from the exposed dermis;[0155]
FIG. 57 is a schematic plan view of a further alternative device having a micro pump for delivering metered quantities of liquid;[0156]
FIG. 58 is a schematic plan view of a further alternative device having a micro pump for sampling quantities of liquid;[0157]
FIG. 59 is an exploded perspective view of a device having an alternative indicator for sensing blister development;[0158]
FIG. 60 is a partly section elevation of a syringe for use in the device of FIG. 59;[0159]
FIG. 61 is a partly sectioned plan view of the syringe of FIG. 60;[0160]
FIG. 62 is a partly sectioned plan view of the device of the syringe of FIGS. 60 and 61 in a retracted configuration;[0161]
FIG. 63 is a schematic sectioned elevation of a further alternative device including a patch applicator;[0162]
FIG. 64 is a schematic underneath plan view of the device of FIG. 63;[0163]
FIG. 65 is a schematic sectioned elevation of the device of FIGS. 63 and 64 following the severing of the blister;[0164]
FIG. 66 is a schematic sectioned elevation of the device of FIGS.[0165]63 to65 following separation of a protective film from the patch;
FIG. 67 is a schematic sectioned elevation of the device of FIGS.[0166]63 to66 after rotation of the actuating ring to place the patch in registration with the aperture;
FIG. 68 is a schematic sectioned elevation of the device of FIGS.[0167]63 to67 after application of the patch;
FIG. 69 is a schematic sectioned elevation of the patch of FIGS.[0168]63 to68 following removal of the device;
FIG. 70 is a schematic sectioned elevation of a conventional skin patch applied over the patch of FIG. 69;[0169]
FIG. 71 shows a schematic sectioned elevation of a modified skin patch overlaying the patch of FIG. 69;[0170]
FIG. 72 is a schematic sectioned elevation of an implementing device which in use overlays a de-epithelialised site and which comprises a porous slab;[0171]
FIG. 73 is a schematic sectioned elevation of an alternative implementing device comprising a cell with a membrane extending across an outlet port;[0172]
FIG. 74 is a schematic sectioned elevation of a further implementing device having a circulating pump and filter;[0173]
FIG. 75 is a schematic sectioned elevation of a further alternative implementing device providing a through flow of liquid;[0174]
FIG. 76 is a schematic sectioned elevation of a further implementing device in which a through flow of liquid is directed to a collecting chamber;[0175]
FIG. 77 is a sectioned elevation of a further alternative implementing device in which a pressurised supply of fluid is released through a flow restrictor to provide a through flow of liquid;[0176]
FIG. 78 is a schematic sectioned elevation of a further alternative implementing device incorporating a bio sensor;[0177]
FIG. 79 is a schematic sectioned elevation of an arrangement in which two separate implementing devices are utilised for sampling and drug delivery;[0178]
FIG. 80 is a schematic sectioned elevation of a further alternative implementing device provided with an electric heating element for heating the contents of the cell;[0179]
FIG. 81 is a schematic sectioned elevation of a further alternative implementing device in which an alternating magnetic field is applied to the contents of the cell;[0180]
FIG. 82 is a schematic sectioned elevation of a further alternative implementing device in which drug is released in a controlled manner by rehydration of a hydrogel polymer;[0181]
FIG. 83 is a schematic sectioned elevation of an alternative implementing device incorporating electrodes for iontophoresis' delivery;[0182]
FIG. 84 is a schematic sectioned elevation of a further alternative implementing device incorporating an osmotic system for drug delivery;[0183]
FIG. 85 is a schematic sectioned elevation of a further alternative device having a semi-permeable membrane;[0184]
FIG. 86 is a schematic sectioned elevation of a further alternative implementing device incorporating a charged polymer membrane;[0185]
FIG. 87 is a sectioned elevation of a dosing device for incrementally delivering liquid doses;[0186]
FIG. 88 is a perspective view of the dosing device of FIG. 87;[0187]
FIG. 89 is a perspective view of a device receiving liquid from the device of FIGS. 87 and 88;[0188]
FIG. 90 is a schematic perspective view of the suction cup, arming device and syringe, further including a modified indicator having a liquid storage structure;[0189]
FIG. 91 is a schematic view of the modified indicator of FIG. 90 showing a slug of liquid being introduced into the tube;[0190]
FIG. 92 is a schematic view of the indicator of FIGS. 90 and 91 showing displacement of the slug of liquid following formation of a suction blister;[0191]
FIG. 93 is a schematic sectioned elevation of an implementing device having releasable connecting means;[0192]
FIG. 94 is a sectioned elevation of the implementing device of FIG. 93 after removal of a closure;[0193]
FIG. 95 is a plan view of a movable portion of a transdermal delivery device cooperable with the implementing device of FIGS. 93 and 94;[0194]
FIG. 96 is a schematic sectioned elevation of a transdermal perfusion device including the movable portion of FIG. 95;[0195]
FIG. 97 is a schematic sectioned elevation of the implementing device of FIGS. 93 and 94 when fitted to the movable portion of FIGS. 95 and 96;[0196]
FIG. 98 is a schematic sectioned elevation of the apparatus of FIG. 97 following actuation of a suction means to draw fluid from a reservoir;[0197]
FIG. 99 is an underneath plan view of a rotatable portion of an alternative device, the rotatable portion being cooperable with a base of the type shown in FIG. 40 and an actuating ring of the type shown in FIG. 46;[0198]
FIG. 100 is a plan view of the rotatable portion of FIG. 99 with the cover plate removed;[0199]
FIG. 101 is a schematic plan view of the device of FIGS. 99 and 100;[0200]
FIG. 102 is a sectional elevation of the device shown in FIG. 101 with the sampling port not in use;[0201]
FIG. 103 is a plan view of the device of FIGS.[0202]99 to102 showing the rotatable portion moved into a position where the sampling port is in use;
FIG. 104 is a sectional elevation of the device shown in FIG. 103 showing the sampling port in use;[0203]
FIG. 105 is a sectional elevation of the device of FIG. 104 after retraction of the sampling piston to a fully retracted position;[0204]
FIG. 106 is a sectional elevation of the device of FIG. 105 after advancing the sampling piston to an intermediate position;[0205]
FIG. 107 is a sectional elevation of the device of FIGS.[0206]99 to106 after fitting of a cuvette to the sampling piston;
FIG. 108 is a side elevation of the cuvette of FIG. 107;[0207]
FIG. 109 is a sectional elevation showing the device of FIG. 107 with the sampling piston fully advanced;[0208]
FIG. 110 is a sectional elevation of the cuvette of FIGS.[0209]107 to109 after removal from the device and insertion into a photometer;
FIG. 111 is a sectional elevation of the device of FIGS.[0210]99 to110 in which a capillary active plug is fitted to the sampling piston;
FIG. 112 is a part sectioned elevation of a further alternative sampling device for use in sampling exudate from a de-epithelialised skin site; and[0211]
FIG. 113 is a part sectioned elevation of the device of FIG. 112 showing the extraction of the sample using a cuvette.[0212]
In FIG. 1 a[0213]first apparatus501 comprises ahousing502 of two-part construction. Thehousing502 consists of adisc503 and an evacuatedcell504 which is similarly of disc-shape and fits onto anupper surface505 of the disc in use.
The[0214]disc503 is formed of a rigid transparent plastics material and has alower surface506 which is coated with adhesive and prior to use is protected by a peel-offpaper film507. Thedisc503 is centrally recessed to define a cup-shapedchamber508 within acylindrical formation509 which projects upwardly of theupper surface505. A cannula510 projects from thecylindrical formation509 in a direction away from thedisc503 so as to define aduct511 communicating with thechamber508. The cannula510 is shown in FIG. 1 in its pre-use configuration in which it is externally covered by aclosed rubber sleeve512.
The[0215]cell504 is formed of a rigid transparent plastics material and encloses aspace513 which is provided at manufacture with a partial vacuum of 200 mm of mercury.
The[0216]cell504 has a lower face514 which is centrally recessed by acylindrical formation515 within which thecylindrical formation509 of thedisc503 is a sliding fit. Thecylindrical formation515 is closed by adisruptable membrane516 formed of rubber.
The[0217]disc503 is of 50 mm diameter and defines a central aperture of 5 mm diameter communicating with thechamber508.
In use the[0218]paper film507 is peeled off and thedisc503 is presented to an area of skin of the patient. Thedisc503 is pressed onto the skin such thatlower surface506 is adhesively secured against the skin and forms an airtight seal. Thecell504 is advanced onto thedisc503 such thatcylindrical formation515 fits over thecylindrical formation509 and the cannula510 ruptures both therubber sleeve512 andmembrane516 to establish communication via theduct511 between thespace513 and thechamber508. A partial vacuum is thereby applied within thechamber508 to an area of skin withinaperture518. Theapparatus501 is held in this position adhesively for two to three hours during which time a suction blister is formed within thechamber508. Formation of the blister can be observed by inspection through the transparent material forming thecell504 anddisc503. The apparatus is then removed from the skin by first removing thecell504 to release the partial vacuum withinchamber508 and then peeling thedisc503 away from the skin.
The exposed blister may then be broken or removed to gain access for transdermal delivery of a drug to the exposed skin dermis or the blister fluid may be sampled for subsequent analysis.[0219]
A[0220]second apparatus520 shown in FIG. 2 comprises ahousing521 which includes a transparent disc-shapedbase522 defining acontact surface523. Thecontact surface523 has an adhesive coating which is protected prior to use by a peel-offpaper film524. Thecontact surface523 is centrally recessed by acylindrical formation525 defining acylindrical chamber526, thecontact surface523 defining acircular aperture527 of 5 mm diameter communicating with thechamber526. The chamber is closed at its other end by adisruptable rubber membrane528.
The[0221]housing521 further comprises acell529 of transparent plastics material which is closed bymembrane528 to enclose a sealedspace530. Thespace530 is evacuated at manufacture to provide a partial vacuum of 200 mm of mercury.
An[0222]actuator pin531 projects sealingly through anouter wall532 ofcell529.Actuator pin531 is axially movable towards themembrane528 so as to form a central puncture in use.
In use the[0223]film524 is peeled off and thecontact surface523 is adhesively secured to the skin of the patient so as to form an airtight seal. Thechamber526 is then closed by an area of skin defined within the aperture533.Actuator pin531 is then advanced so as to rupture themembrane528 and air moves through the ruptured membrane to equalise pressure in thespace530 andchamber526. A partial vacuum is thereby applied to the area of skin exposed within the aperture533. Thechamber526 and thespace530 together constitute a closed compartment in which a partial vacuum is maintained so long as the ingress of air is prevented by the airtight seal between the contact surface and the skin. Theapparatus520 is left in situ for a period of about two hours during which time the formation of asuction blister534 is observed through thetransparent housing521 as shown in FIG. 3. In FIG. 3 theactuator pin531 is shown in an orientation in which it is rotated through 90° relative to the position shown in FIG. 2 thereby revealingcutting edges535 which disrupt theblister534 as shown in FIG. 4 when the actuator pin is further advanced.
The contents of the[0224]blister534 may be sampled and analysed or a skin patch (not shown) may be applied over the site of the broken blister to apply a liquid drug to be perfused through the exposed dermis.
A[0225]third apparatus540 is shown in FIG. 5 and will be described using corresponding reference numerals to those of FIGS. 2, 3 and4 where appropriate for corresponding elements.
[0226]Apparatus540 similarly has atransparent housing521 with acell529 enclosing an evacuatedspace530 and suction is applied throughaperture527 incontact surface523 by creating a partial vacuum inchamber526 by disrupting amembrane528. Theapparatus540 includes a pull-ring actuator541 to which is attached afirst end542 of awire543 of which asecond end544 is anchored in themembrane528. Thewire543 is enclosed within asheath545 which is sealed to both theouter wall532 of thecell529 and themembrane528.
In use the pull-[0227]ring actuator541 is pulled to displace thewire543 so that thesecond end544 is pulled through themembrane528 leaving a hole through which air flows between thechamber526 andspace530. A partial vacuum is thereby applied to thechamber526 for the formation of a skin blister. The partial vacuum then persists in the closed compartment constituted bychamber526 andspace530 so long as an airtight seal across the aperture is provided by adhesive contact with the skin.
A[0228]fourth apparatus550 is shown in FIG. 5 and will be described using corresponding reference numerals to those of FIG. 2 where appropriate for corresponding elements.
[0229]Apparatus550 comprises atransparent housing521 having acontact surface523 and an evacuatedcell529. Acylindrical formation525 defines achamber526 which is closed by adhesion of thecontact surface523 to an area of skin and partial vacuum within thechamber526 is then applied by disruptingside walls551 of thecylindrical formation525 by means of laterally extendingactuator pins552 and553. Operation of theapparatus550 is in other respects similar to that ofapparatus520.
In FIG. 7 a[0230]fifth apparatus560 comprises a disc-shapedbase561 defining acentral aperture562 which communicates directly with achamber563 defined by abellows564. The bellows564 is biassed bycoil springs565 and566 into an extended position as shown in FIG. 8. Theapparatus560 is normally stored in its compressed state as shown in FIG. 7 and thebase561 defines acontact surface567 which is adhesively coated and is provided pre-use with aprotective film568. Thefilm568 closesaperture561 in this condition to prevent ingress of debris during storage.
The[0231]bellows564 is clamped in its compressed condition by means of a clamp (not shown) and an actuator (not shown) is provided to release the clamp to allow the bellows to expand to its expanded configuration shown in FIG. 8.
In use the[0232]film568 is removed and thecontact surface567 applied to the skin so thataperture562 is closed in airtight manner by an area of skin. The actuator is operated to unclamp thebellows564 and the bellows expand by spring action to thereby increase the volume ofchamber563 and this results in the creation of a partial vacuum which is applied to the area of skin exposed byaperture562. Theapparatus560 is left in situ for a period of about two hours and may then be removed first by compressing the bellows to its original shape to remove the partial vacuum and then peeling off the contact surface from the skin. The blister may then be broken or removed and a transdermal skin patch applied to the exposed dermis.
A sixth apparatus[0233]570 is shown in FIG. 9 and comprises adisc571 which is axially mounted on ashaft572. Thedisc571 has aflat contact surface573 from which a plurality of sharp edged protrusions574 project towards the skin. The protrusions574 have a height corresponding to the depth of epidermis and in use the contact surface is placed against the skin and the disc rotated by means ofshaft572 to thereby form incisions in the epidermis. The apparatus570 is then removed and a skin patch containing a drug is then applied to the area of skin in which the incisions are formed.
A[0234]seventh apparatus580 is shown in FIGS. 10, 11 and12 and comprises ahousing581 consisting of anannular frame582 which is adhesively secured to an area ofskin583 in use. Ade-epithelialising apparatus584 is releasably locatable within theannular frame582 and in FIGS. 10 and 11 thede-epithelialising apparatus584 is of the type described above with reference to FIGS. 2, 3 and4 in which a suction blister is formed and ruptured by actuation of anactuator pin585. In FIG. 10 thede-epithelialising apparatus584 is shown in situ prior to use. In FIG. 11 the de-epithelialising apparatus is shown separated from theframe582 after formation and rupturing of the blister (not shown). FIG. 12 shows a drug delivery module586 located within theframe582 following removal of thede-epithelialising apparatus584. The drug delivery module586 comprises a disc-shapedcasing587 having acentral drug compartment588 which includes asemi-permeable membrane589 through which the drug exudes at a predetermined rate. (Detail of the ruptured blister is omitted from FIG. 12).
The[0235]casing587 is configured to be a close fit within theframe582 and to locate themembrane589 over the location of the area of skin which is de-epithelialised by theapparatus584.
The diameter of the[0236]membrane589 is greater than the diameter of the de-epithelialised skin patch to take account of any errors in positioning.
The apparatus of FIGS.[0237]10 to12 may alternatively utilise the apparatus of FIG. 9 in achieving de-epithelialising of the skin, the apparatus570 being located within theframe582 and removed prior to insertion of drug delivery module586.
An alternative[0238]drug delivery module590 is shown in FIG. 13 and comprises areservoir591 containing a volume of drug, the reservoir being held by anannular support592 in proximity withskin surface593. Thesupport592 defines a narrowbore connecting tube594 communicating between thereservoir591 and arecess595 which is defined by the support and overlays the de-epithelialised skin area. Liquid drug is progressively fed by capillary action through the connectingtube594 into the recess and hence is perfused through the exposed dermis.
The flow of liquid through the connecting tube may be aided by the application of positive pressure to the[0239]reservoir591.
In FIG. 14 an eighth apparatus[0240]600 for the transdermal delivery of a drug comprises a transparent housing601 with a disc-shapedbase602. Acontact surface603 is adhesively coated so as to adhere to a skin surface and the base defines acentral aperture604 communicating with a chamber605 formed by acylindrical formation606.
The[0241]cylindrical formation606 is closed at one end by afrangible membrane607 which initially separates the chamber605 from an evacuatedspace608 provided by acell609 of the housing601.
The[0242]frangible membrane607 is disruptable by means of anactuator pin610 of the type described above with reference to FIGS. 2, 3 and4 so that actuation of thepin610 ruptures the membrane to introduce partial vacuum into the chamber605 during a blister forming period. Further actuation of thepin610 advances the pin to a position in which it will disrupt the blister to expose the dermis within the chamber605.
Apparatus[0243]600 also comprises an integrally formeddrug reservoir611 which is normally sealed by afrangible plug612. Adrug release actuator613 is provided for breaking theplug612 and allowing the drug to flow into the chamber605.
In use the apparatus[0244]600 is placed on the skin such that adhesion between thecontact surface603 and skin provides an airtight seal across theaperture604. The actuator pin is then advanced to disrupt themembrane607 so that a partial vacuum is produced in the chamber605 to form a blister. The cell and chamber together constitute a closed compartment sealed by the area of skin and in which partial vacuum persists during a blister forming period. The blister is then ruptured by further actuation ofactuator pin610 and thedrug release actuator613 is then operated to allow drug into the chamber605. De-epithelialised dermis exposed by rupturing the blister is then exposed to the drug and transdermal perfusion then proceeds.
In FIG. 15 a[0245]ninth apparatus620 includes an apparatus for transdermal drug delivery such as that described with reference to FIG. 14 (details of such transdermal apparatus are not shown in FIG. 15) and additionally includes aninjection device621 which is operable to inject via acannula622 an initial dose of drug prior to de-epithelialisation and transdermal delivery by means of the transdermal apparatus using an adjacent patch of skin. Such immediate administration of a dose is useful in administering pain relief for example or control of premature muscle contractions of the uterus during pre-term labour.
The[0246]injection device621 comprises anadditional suction cup623 defining asuction chamber624 to which suction is applied to immediately draw skin into the chamber as shown in FIG. 16. Thecannula622 is located within the chamber in a position such that skin drawn into the chamber by suction is penetrated. Drug is then injected through the cannula from areservoir625 on release of avalve626. Drug within thereservoir625 is pressurised by means of an expandingdevice627 placed in contact with thereservoir625 which is formed of a deformable material so as to be collapsible.
A[0247]tenth apparatus630 shown in FIG. 17 comprises ahousing631 having anannular contact surface632 defining anaperture633. Thehousing631 is centrally recessed to define achamber634 communicating with the aperture.
The[0248]housing631 incorporates anannular drug reservoir635 peripherally disposed relative to theaperture633 and includes an evacuated cell636 which is isolated from thechamber634 prior to use by adisruptable membrane637.
The[0249]housing631 has anactuator cap638 which is movable relative to abase portion639 which includes thecontact surface632.
[0250]Apparatus630 is arranged to provide for the formation and disruption of a suction blister and for subsequent drug delivery to the exposed dermis by successive actuation of theactuator cap638.
The[0251]housing631 is initially secured to a patch of skin such that theaperture633 is closed in a sealed manner by an area of skin through which drug is to be transdermally delivered. Thehousing631 is secured by means of a peripheral support frame (not shown).
As shown in FIG. 18 the[0252]actuator cap638 is pressed towards thebase portion639 so as to advance acannula640 so as to penetrate themembrane637 and place thechamber634 in communication with the evacuated cell636. A partial vacuum is thereby created within thechamber634 and the partial vacuum persists during a blister forming period by virtue of thecontact surface632 being sealed against the skin.
After a period of two hours the[0253]actuator cap638 is rotated through 45° as shown in FIG. 19 in response to which motion air is admitted to thechamber634 through a release valve (not shown) so as to restore atmospheric pressure and ablister disrupting fin641 moves into thechamber634 and breaks or removes the roof of the blister formed within the chamber. Thefin641 includes anabsorbent layer642 which absorbs blister fluid released by this motion.
The[0254]actuator cap638 is again further advanced as shown in FIG. 20 through a rotational movement of 45° and this further motion opens a valve to release a liquid drug from thereservoir635 through anoutlet143 into thechamber634.
Transdermal perfusion of the drug through the exposed dermis of the skin then proceeds.[0255]
An[0256]eleventh apparatus650 shown in FIG. 21 also includes anactuator cap651 which provides successive operations of blister formation, blister disruption and drug release by successive stages of movement of the cap relative to abase portion652 of ahousing653. Thehousing653 includes adisc portion654 having a flat disc-shapedcontact surface692 defining acentral aperture655 of 5 mm diameter. Theaperture655 communicates with achamber656 defined by acylindrical formation657 projecting upwardly of the disc portion.
The[0257]housing653 includes acell658 bounded on one side by thedisc portion654 and defining aclosed space659. Thehousing653 also includes adrug reservoir660 which is separated from thespace659 by apartition661 extending parallel to thedisc portion654.
The volume of the[0258]drug reservoir660 is variable by movement of apiston662 which is movable towards thepartition661 to reduce the volume of the reservoir for the purpose of expelling liquid drug.
The[0259]housing653 is cylindrical in shape and theactuator cap651 is similarly cylindrical and overlays the housing, the housing and cap having cooperatingscrew threads663 whereby rotation of the cap relative to the housing advances the cap towards thedisc portion654.
A[0260]hollow needle664 is mounted axially within thecap651 such that rotation of the cap produces axial movement of the needle relative to the housing.
In FIG. 21 the[0261]apparatus650 is shown in its initial rest position in which theneedle664 projects sealingly through thepiston662.
The[0262]partition661 includes acentral orifice665 which is normally sealed by arubber plug666. Therubber plug666 is in axial alignment with theneedle664 and with amembrane seal667 forming part of thecylindrical formation657 and normally separating thechamber656 from thespace659 withincell658.
The[0263]piston662 is biassed in a direction towards thepartition661 by means of acoil spring668 and the piston is restrained against axial movement by means of acatch669 which is releasable by rotation of thecap651 in a manner described below.
The[0264]hollow needle664 has aside hole670 which in the rest position shown in FIG. 29 is located above thepiston662 so as to be outside of thedrug reservoir660. The piston is provided with upper and lower slidingseals710,711 respectively which “bracket” theside hole670 and prevent entry of air.
The[0265]needle664 also has anindentation671 located intermediate theside hole670 and theneedle tip672.
Rotation of the[0266]piston662 relative to thebase portion652 is prevented by means of a locatingpin673 which is received in a cooperatingrecess674 of the piston.
The[0267]cell658 is evacuated to have a partial vacuum of 200 mm of mercury.
The apparatus is prepared for use by removing a protective film to expose an adhesive[0268]coated disc portion654, thecell658 being evacuated and thedrug reservoir660 being initially empty.
In use, the[0269]housing653 is attached to the skin of the user such that thedisc portion654 is adhesively sealed to an annular area ofskin693 peripheral to atreatment site696.Central aperture655 is thereby sealed against ingress of air which thereby closes thechamber656. Suction is applied at thetreatment site696 by actuation of thecap651 so as to advance theneedle664 through both therubber plug666 and themembrane seal667. Themembrane seal667 is formed of a frangible material which fractures and provides for the passage of air between thespace659 and thechamber656 thereby reducing the pressure within the chamber. Therubber plug666 maintains sealing engagement with theneedle664 so that no air enters thespace659 from thereservoir660. Air cannot enter thechamber656 through theneedle664 since theside hole670 remains sealed by theseals610,611.
A partial vacuum is maintained within the closed compartment constituted by the[0270]space659 and thechamber656 during a blister forming period, the ingress of air being prevented by an adhesive seal between thedisc portion654 and the annular portion ofskin693.
The formation of a blister is illustrated in FIG. 22 which shows the position of the needle during the blister forming period. The blister consists of a raised portion of[0271]epidermis695 which is ‘delaminated’ from thedermis694 to which it is normally attached.
Once a blister has been formed after a period of two hours a further rotational movement of the[0272]cap651 is required to further advance theneedle664 to the venting position shown in FIG. 23 in which theindentation671 comes into registration with therubber plug666 thereby allowing air from thereservoir660 to enter thespace659 to restore atmospheric pressure.
At this stage a quantity of drug is inserted into the[0273]reservoir660 through adrug insertion port675 of the type shown in FIG. 28. Although not shown in FIG. 21 theinsertion port675 is located so as to provide a means of injecting liquid drug through the housing into thereservoir660.
The[0274]drug insertion port675 comprises aduct676 communicating with thereservoir660 and closed by a self-healingrubber bung677 through which a syringe needle is insertable.
After filling the[0275]reservoir660 with a liquid drug a further movement of theactuator cap651 rotates the cap to a position in which theside hole670 is located within thereservoir660 and at the same time thecatch669 operates to release thepiston662. Under the action of thespring668 thepiston662 pressurises liquid within thereservoir660 which flows into theneedle664 through thehole670 and emerges from theneedle tip672 into thechamber656. By this further advancement of the needle theblister678 is ruptured so that drug within thechamber656 comes into contact with the exposed dermis679 so that transdermal delivery of the drug is commenced.
As shown in FIG. 24 the[0276]needle664 includes amicroporous filter680 adjacent theneedle tip672 by means of which the flow of liquid into thechamber650 is restricted. This slows the rate of release of drug into thechamber656 and ensures a gradual release of drug at a predetermined rate.
The[0277]housing653 is held in situ for a period during which transdermal delivery proceeds and this period may extend to four days by which time the self-healing of the epidermis will begin to provide a barrier preventing direct access to the dermis.
The construction of the[0278]catch669 is illustrated in FIG. 25 which shows three circumferentially spacedfeet681 which are connected to thepiston662 bylegs682 such that the feet normally engage a supportingannular track683 attached to thecap651. Thetrack683 is provided with cut-outs684 into which thefeet681 fall to release thecatch669 when the cap is rotated to its final position.
During rotation of the[0279]cap651 relative to thebase portion652 the cap is advanced axially by screw action. In order to prevent thepiston662 advancing until released by thecatch669 thetrack683 is ramped to provide a compensating axial movement of the piston relative to the cap so that the piston remains stationary relative to thebase portion652.
Rotation of the[0280]cap151 relative to thebase portion652 is stepped by use of suitable snap fitting detents and corresponding recesses (not shown) on the cap and base portion respectively. As shown in FIG. 26, suitable markings are provided on thecap651 andbase portion652 to indicate the sequential steps of rotation.
The[0281]drug insertion port675 may be replaced by adrug filling port685 of the type shown in FIG. 29 in which a duct686 is normally closed by a hingedsnap fitting closure687. Drug is therefore introduced into thereservoir660 by opening theclosure687, pouring the drug in and replacing the closure.
The[0282]space659 may be provided with a partial vacuum at manufacture or alternatively the partial vacuum within thespace659 may be produced immediately before use by withdrawing air through a suction port688 of the type shown in FIG. 28. Suction port688 comprises aduct689 communicating with thespace659 via a non-return valve690, theduct689 being defined by aLuer connector691 into which the hub of a syringe can be sealingly inserted. Suction created by reverse actuation of the syringe will thereby withdraw air through the non-return valve690 from thespace659 to create a partial vacuum. The syringe is withdrawn from theconnector691 and thecell658 is then sealed automatically by action of the valve690 before attachment of thehousing653 to the skin.
The[0283]housing653 may be attached to the skin of an arm or leg in the manner shown in FIG. 29 where anadhesive strip700 extends around thelimb701. Alternatively as shown in FIG. 30 an annularadhesive film702 may attach thehousing653 to a localised area of skin thereby contributing to the airtight seal formed between thedisc portion654 and the skin but without any further means of holding the housing in situ.
As shown in FIG. 32 the arrangement of FIG. 30 can be supplemented by the addition of a strap fastened using a hook-[0284]loop fastener703 as illustrated in FIG. 33.
In the above embodiments the adhesive used in contact with the skin may be of a hydrocolloidal type composed of pectin and gelatine or may alternatively be composed of acrylic or silicon. In each case the apparatus may be supplied with the adhesive covered in a protective sheet which also seals the aperture formed in the contact surface and the entire assembly can be sterilised in readiness for use.[0285]
The[0286]fifth apparatus560 of FIGS. 7 and 8 may be provided with alternative means of expanding thechamber563. For example a screw type arrangement or piston arrangement may be used to expand the enclosed chamber.
The contact surface may be sealed to the skin other than by the use of adhesive if required. For example the contact surface may be provided with projecting ribs which sealingly engage the skin surface and in such an arrangement the apparatus should be held firmly in place for example by straps.[0287]
Apparatus in accordance with the present invention may be provided with more than one evacuated cell to allow the partial vacuum to be re-established for example for the purpose of removing a self-healed epidermal barrier or to remove by suction any blister fluid within the chamber.[0288]
It may be desirable to provide apparatus in which the contact surface is interchangeable to provide apertures of different size.[0289]
The size of the de-epithelialised area of skin may also be stretched by applying stretching means to the surrounding skin.[0290]
In the examples referred to above the aperture size of 5 mm may be varied typically in the[0291]range 1 mm to 10 mm.
The drug may be applied in a form producing slow release, for instance by reversible binding in absorbent biodegradable starch particles, polymer(s), in non-biodegradable polysaccharide spheres, or in microcapsules consisting for instance partly of lipids or polymers of different types which may break or disintegrate slowly in biological fluids.[0292]
The drug may be applied in so-called pro-drug form, allowing it to pass through the tissue into the blood with minimal break-down (this being an important aspect in peptide delivery).[0293]
The re-epithelialisation of the drug delivery site can be delayed for instance by applying a steroid drug in addition to the therapeutic agent. Other means, for instance addition of antibodies to epithelial cells, may be used for the same purpose. The apparatus could be pre-loaded with such an agent, it could be added to the drug solution or taken by other routes.[0294]
The apparatus of FIGS.[0295]1 to6,14 to20 may be provided with a suction valve of the type described with reference to FIG. 28.
The apparatus of FIGS.[0296]17 to20 and of FIGS.21 to26 may be modified to include an expansion means of the type described with reference to FIG. 7. The apparatus may also optionally include a valve for interrupting the delivery of drug in use.
In the above embodiments reference is made to the delivery of drugs in liquid form. The apparatus may also be used to deliver gels and creams with suitable modification where appropriate.[0297]
FIG. 34 shows a[0298]further device1 for use in the transdermal delivery of a liquid drug in contact with a de-epithelialised area of skin and for initially de-epithelialising the skin by formation and subsequent disruption of a suction blister.
The[0299]device1 comprises ahousing2 consisting of abase3 secured in contact with a patient'sskin4 and having arotatable portion5. Thebase3 is disc shaped and therotatable portion5 generally cylindrical and coupled to the base so as to be rotatable relative to the base about its cylindrical axis in continuous sliding contact with the base.
A[0300]circular aperture6 is defined in thebase3 at a location eccentric relative to the cylindrical axis of therotatable portion5. In the rest position of the device shown in FIG. 34, acylindrical access port7 defined in therotatable portion5 is aligned in communication with theaperture6 such that a circular area ofskin8 is accessible through thedevice1.
A[0301]suction cup9 is located in theaccess port7 and has a flaredlip10 of greater diameter than theport7 such that the suction cup is captively retained. Thebase3 is recessed peripherally of theaperture6 to accommodate thelip10. The internal surfaces of thecup9 are coated with acrylic adhesive so that, once a suction blister is formed in the cup, the surface of the blister will adhere to the cup, thereby maintaining the blister in an elevated position. This will tend to prevent collapse of the blister in the event of accidental rupture.
The[0302]rotatable portion5 also accommodates areservoir11 containing a liquid drug, thereservoir11 being isolated from theaccess port7 in the position shown in FIG. 34.
The[0303]suction cup9 has afemale connector13 which is engagable with amale connector14 of asuction tube15 via which suction can be applied in use to asuction chamber16 defined within thesuction cup9. In FIG. 34, the device is shown in its rest position following the application of suction within thechamber16 for a period sufficient to result in the formation of asuction blister17, following which the male andfemale connectors13 and14 have been disconnected from one another to admit air at ambient pressure to thechamber16.
The[0304]device1 also includes ablade18 which extends radially with respect to the cylindrical axis of therotatable portion5 and which is movable by rotation about the cylindrical axis in a plane defined by the interface between thebase3 and therotatable portion5.
In FIG. 35 the operation of the[0305]blade18 is illustrated in that it has been moved arcuately so as to cut through thesuction cup9 at a location which is intermediate the roof of thesuction blister17 and theaperture6. By this cutting action, thesuction cup9 is severed into acaptive portion19 extending through thebase3 and aremovable portion20 extending through therotatable portion5 and to which theroof21 ofsuction blister17 remains adhered.
By withdrawing the[0306]removable portion20 from theaccess port7, theroof21 may thereby be disposed of. Since theremovable portion20 is severed at the interface between thebase3 and therotatable portion5, the severing action of theblade18 thereby allows therotatable portion5 to be subsequently movable by rotation relative to thebase3 whereas previously the presence of the suction cup extending through theaperture6 and accessport7 prevented such relative rotational movement about the cylindrical axis.
The[0307]reservoir11 has anoutlet port22 which in the rest position of therotatable portion5 as shown in FIGS. 34 and 35 is closed by anupper surface23 of thebase3, a continuous O-ring seal24 being interposed between thesurface23 and therotatable portion5 to prevent peripheral leakage from theoutlet port22. Following the severing of thesuction cup9, therotatable portion5 is rotated into a second position shown in FIG. 36 in which theoutlet port22 is brought into registration with theaperture6, the location of theoutlet port22 being spaced radially from the cylindrical axis of therotatable portion5 about which it is rotated.
The O-[0308]ring seal24 is maintained in a fixed position relative to therotatable portion5 so that in this second position it forms a peripheral barrier between therotatable portion5 and theupper surface23 of thebase3. Thedrug12 within thereservoir11 then enters thechamber16 and comes into contact with the area ofskin8 which has been de-epithelialised following removal of thesuction blister17. Thedevice1 is retained in this second position during a drug delivery phase of operation in which the drug is absorbed into the patient.
On completion of this phase, the[0309]rotatable portion5 is again rotated and moved into a third position shown in FIG. 37. In this third position, theoutlet port22 of thereservoir11 is again closed by theupper surface23, assisted by the sealing action of the O-ring seal24. A second O-ring seal25 is brought into peripheral sealing engagement between theupper surface23 and therotatable portion5 at a location peripheral to theaperture6 thereby providing an air tight seal to thechamber16.
The[0310]rotatable portion5 may subsequently be returned to the second position should further drug delivery be required or thedevice1 may be removed from the patient on completion of the procedure.
The above FIGS.[0311]34 to37 are schematic in nature and serve to illustrate the function of the above mentioned elements. The detailed construction of these elements will now be described in the context of a specific embodiment of the invention.
In FIG. 38 the[0312]suction cup9 is shown to comprise acylindrical portion26 defining thechamber16 and which in use is severed radially by action of theblade18 into captive andremovable portions19 and20. The internal surfaces of thesuction cup9 are coated with an acrylic adhesive incorporated with random oriented polyester fibres.
The[0313]removable portion20 terminates in thefemale connector13 to which it is connected by a frustoconicaltapered portion27. Themale connector14 is connected by aflexible web28 to thefemale connector13 such that when disconnected from one another they are retained in loose association. An armingdevice29 is connected to themale connector14 and consists of aplate30 through which thesuction tube15 passes, the plate being formed integrally with an outwardly projectinghandle31 and an oppositely projectingbifurcated arming pin32. The armingdevice29 is shaped such that it must be inserted within therotatable portion5 in order for the male andfemale connectors14 and13 to be engaged, the presence of the inserted armingpin32 being arranged to prevent movement of theblade18 from its initial position as shown in FIG. 34. This arrangement thereby ensures that theblade18 cannot be moved until the armingdevice29 has been disengaged from therotatable portion5 and this disengagement also necessitates disengagement of the male andfemale connectors14 and13 so that suction can no longer be maintained in thechamber16. This is a safety feature of thedevice1 which is intended to avoid cutting thesuction blister17 while there is any suction within thechamber16 which could displace the underlying dermis into a position in which it extends into the chamber sufficiently to be damaged by the blade.
The[0314]suction tube15 is connected to asyringe33 comprising apiston34 slidable within acylinder35 and spring biassed into the position shown in FIG. 38 in which the syringe volume is a minimum. The syringe is provided with alocking mechanism36 enabling thepiston34 to be held in a withdrawn position corresponding to maximum syringe volume so that suction can be applied to thechamber16 by engaging the male andfemale connectors14 and13 and then withdrawing the piston and locking the piston in place by means of the locking mechanism.
The[0315]suction tube15 is formed of a transparent and flexible plastics material and contains a slug ofliquid37 forming part of anindicator38.
The[0316]indicator38 comprises a clampingring39 which is a tight fit on the external surface of thesuction tube15 but can be adjusted in position along the length of the tube so as to bring into registration with the slug of liquid37 alinear scale40. When suction is initially applied to thechamber16 by action of thesyringe33, the position of the slug ofliquid37 will move due to displacement of air along thetube15 to a new position and the operator using thedevice1 at this time adjusts the position of the clampingring39 such that the end of the slug ofliquid37 is aligned with a zero marking on thescale40. Suction is maintained with thechamber16 during a blister forming period in which thesuction blister17 will progressively form and grow in size until it extends into thecylindrical portion26. In doing so theblister17 will displace air within thetube15 and consequently the slug ofliquid37 will be linearly displaced relative to thescale40. Thescale40 is calibrated such that the operator is able to determine the extent of displacement of the slug of liquid37 corresponding to theblister17 being fully formed to a predetermined level at which a predetermined volumetric displacement within thechamber16 is achieved.
By visual inspection of the[0317]indicator38 it is therefore possible for the operator to determine when the blister forming phase of operation is completed.
At this stage the operator will grip the[0318]handle31 and pull thearming device29 so as to withdraw the armingpin32 and at the same time to disconnect themale connector14 from thefemale connecter17. Suction within thechamber16 will then be lost.
FIG. 39 shows the[0319]device1 in greater detail with the suction cup omitted for clarity. Thebase3 has acentral socket41 in which an axially projecting pin formed integrally with therotatable portion5 is journaled thereby enabling the rotatable portion to be rotatable about its cylindrical axis relative to thebase3. Therotatable portion5 is retained in axial abuttment with thebase3 by retainingflanges43 which project radially inwardly from circumferentially spacedaxial projections44 formed integrally with thebase3.
The[0320]rotatable portion5 is provided with a partannular rim45 which projects radially outwardly so as to engage theprojection44.
An[0321]actuating ring46 is mounted on therotatable portion5 and is captively retained by cooperatingflange formations44. Theactuating ring46 is capable of limited angular displacement relative to therotatable portion5 for the purpose of moving theblade18 relative to therotatable portion5 andbase3 when the latter are locked together by the presence of the suction cup.
The shape of the[0322]base3 is shown more clearly in FIGS. 40 and 41. Thebase3 comprises adisc48 in which thesocket41 is centrally formed and theaperture6 is eccentrically located. Atapered seat49 surrounds theaperture6 and is shaped to conform to thelip10 of the suction cup so that when the suction cup is inserted in theaperture6 thelip10 remains flush with theunderside50 of thedisc48. Thedisc48 is provided with laterally projectingwings51 to assist in stably securing the disc to the patient's skin. Theunderside50 comprises an adhesive layer enabling thedisc48 to be secured to the skin in a secure and air tight manner so that in use with the suction cup evacuated the patient's skin forms a sealed closure to thechamber16.
FIG. 42 shows the[0323]rotatable portion5 in plan view omitting atop cover plate52 shown in FIG. 39 which in the completed device is heat welded to amain body53 of therotatable portion5 so as to close thereservoir11. Themain body53 consists of a planar bottom54 with an upstandingperipheral wall55 which is part circular to define therim45 and includes acylindrical wall portion56 defining theaccess port7.
The bottom[0324]54 includes a raised figure of eightprofile57 which accommodates arecess58 on the underside of the bottom54 which receives integrally formed seals24 and25.
FIG. 44 shows the shape of the[0325]cover plate52 which is that of a disc with a cut out58 provided to allow insertion of the armingpin32.
FIGS. 46 and 47 show the[0326]actuating ring46 which has four circumferentially spaced snap fit retainingflanges59 forming part of theflange formations47 and thereby securing the actuating ring to therotatable portion5.
As shown in FIG. 47 the[0327]actuating ring46 includes adrive pin60 which locates in a locatinghole61 at the outer radial extremity of theblade18 as shown in FIG. 48. Rotation of the actuating ring relative to therotatable portion5 will thereby cause theblade18 to rotate about an innerradial pivot63 which is coaxial with the cylindrical axis of therotatable portion5.
A[0328]resilient detent63 is also provided adjacent thedrive pin30 and projects radially inwardly in the manner of a ratchet so as to cooperate with a rampedstop64 formed on therotatable portion5 as shown in FIG. 42. Thedetent63 and stop64 prevent reverse rotation of theactuating ring46 relative to therotatable portion5 after completion of an initial stage of rotation between an initial position of the actuating ring (FIGS. 39, 48 &49) and an actuated position (FIG. 50).
FIG. 48 shows the[0329]base3 assembled with therotatable portion5 and theactuating ring46 but with the suction cup not being shown.
The[0330]device1 in FIG. 48 is shown with theblade18 in its initial position and with the armingdevice29 in place so that relative movement between the actuatingring46 and therotatable portion5 is prevented by the presence of the armingpin32.
Also shown in FIG. 48 is a[0331]plug65 which closes a fillingport66 provided in thecover plate52 to facilitate filling of thereservoir11.
FIG. 49 shows the[0332]device1 after removal of the armingdevice29, thepin60 anddetent63 being thereby exposed in plan view.
FIG. 50 shows the[0333]device1 after subsequent rotation of theactuating ring46 relative to therotatable portion5 from the initial position to the actuated position corresponding to the actuated position by the blade indicated schematically in FIG. 35. In this actuated position, theblade18 is seen to have traversed theaccess port7 and will therefore have severed thesuction cup9 and suction blister17 (not shown in FIG. 50). In this actuated position thedetent63 can also be seen to have moved beyond thestop64 and will subsequently prevent rotation of theactuating ring46 relative to therotatable portion5.
FIG. 51 illustrates further clockwise rotation of the[0334]actuating ring46 in unison with therotatable portion5 relative to thebase3 into the second position of the rotatable portion represented in FIG. 36. In this second position theoutlet port22 of thereservoir11 is brought into registration with theaperture6 and the contents of thereservoir11 enter thechamber16. Absorption of theliquid drug12 then occurs during a transdermal delivery phase of operation of the device.
FIG. 52 shows the final stage of operation in which reverse (anti-clockwise) rotation of the[0335]actuating ring46 in unison with therotatable portion5 relative to thebase3 moves the rotatable portion into the third position represented in FIG. 37. In this position theoutlet port22 of thereservoir11 is closed and the ingress of air is prevented by the second O-ring seal25 cooperating between theupper surface23 of thebase3 and the bottom54 of therotatable portion5.
The[0336]device1 may be modified to include more than oneoutlet port22 as illustrated schematically in FIG. 53 which shows in plan view the interior of a modifiedrotatable portion70. The modifiedrotatable portion70 may be incorporated in a device similar to that shown in FIG. 34 and will therefore be described using corresponding reference numerals where appropriate for corresponding elements.
The[0337]rotatable portion70 includes' anaccess port7 through which a suction cup is inserted in the manner illustrated in FIG. 34, subsequent operation of the device being such as to form a blister and sever the suction blister using ablade18 as shown in FIG. 50 to provide an exposed area ofde-epithelialised skin8 accessible through the access port.
The modified[0338]rotatable portion70 however provides a number ofalternative outlet ports22 as shown in FIG. 53 which are circumferentially distributed around a circle passing through theaccess port7 such that by rotation of therotatable portion70 any one of theoutlet ports22 can be brought into registration with the area ofskin8 from which a blister roof has been removed.
The modified[0339]rotatable portion70 comprises a series ofcompartments71 which are divided from one another byradial partitions72. Thecompartments71 may therefore constitutereservoirs11 whose operation corresponds to that ofreservoir11 described with reference to FIG. 34 above for containing respective quantities of liquid which is to be brought into contact with the area ofskin8. The respective liquids may be drugs of different type, quantities of the same drug having different strength, or drugs contained in different preparation (such as gel, solid or liquid form for example).
Operation of a[0340]device1 incorporating a modifiedrotatable portion70 therefore facilitates sequential administration of different stages of treatment according to which of theoutlet ports22 is brought into registration with the area ofskin8.
Alternatively, one or more of the[0341]compartments71 may be utilised for a purpose other than containing liquid and may for example contain a bio sensor73 for sampling body fluids exuding from the area ofskin8 following de-epithelialisation. In FIG. 53, the use of such a bio sensor73 for the purpose of sampling and analysing exudate is illustrated schematically in one of thecompartments71.
The[0342]device1 of FIGS.34 to53 relies upon manual actuation of anactuating ring46 in order to achieve relative movement between therotatable portion5,70 and thestationary base3. In order to assist the user in overcoming frictional forces between the relatively rotatable components, thedevice1 may be modified as shown in FIG. 54 to include an actuating mechanism74 operable to achieve a mechanical advantage between movement of an actuatingmember75 and therotatable portion5.
In the embodiment of FIG. 54, the actuating[0343]member75 consists of a rotatable key which is connected for rotation with a gearedpinion76 which engages acircumferential rack77 formed peripherally of therotatable portion5.
The user may thereby more readily rotate the rotatable portion relative to the[0344]base3 by winding the actuatingmember75, the gear ratio in this example being 3:1.
The[0345]device1 as described in any of the alternative embodiments may optionally include a heating means comprising aheating element78 as shown in FIG. 55. Theheating element78 comprises an annular resistive sheet connected to thebase3 so as to define an annularheated surface79 which is flush with an underneath side80 of thebase3 and therefore is held in contact with theskin4 in use.
In the example of FIG. 55 the[0346]heated surface79 has an external diameter of 10 millimetres and an internal diameter of 8 millimetres. Theheating element78 is connected to a power circuit (not shown) operable to pass electric current through the heating element sufficient to maintain the element at a controlled temperature of 41° C.
The power circuit may be operable to sense the temperature of the[0347]heating element78, typically by measuring its resistance, and may control actively the current passing through the heating element in order to maintain the required temperature. Alternatively theheating element78 may be formed of a material selected to have a coefficient of resistance which achieves self regulation at the required temperature when supplied from a constant voltage power supply.
The[0348]heating element78 extends peripherally of thechamber16 so as to warm theskin4 during exposure to suction in the blister forming stage of operation of thedevice1. The application of such warming decreases the time required for formation of the blister so that the use of the device is rendered more convenient and less subject to variation from patient to patient.
The controlled temperature is preferably maintained in the[0349]range 36° C. to 43° C.
The heating means may alternatively be energised by other means such as exothermic chemical reaction, the reaction being effected in a localised manner by known means and arranged to deliver heat to an annular heated surface corresponding to surface[0350]79 in FIG. 55.
A further optional feature which may be incorporated in any of the embodiments of the device disclosed herein is shown in FIG. 56 and comprises a[0351]brush81. Thebrush81 is connected to therotatable portion5 at a location such that during rotation of the rotatable portion the brush passes across theaperture6 and extends into contact with the de-epithelialised area ofskin8. Thebrush81 is formed of resilient bristles and is arranged so as to normally lie flat between the opposed surfaces of therotatable portion5 and thebase3, the brush resiling to extend automatically into theaperture6 when suitably aligned.
The use of such a[0352]brush81 may be advantageous in that residual portions of epidermis following rupture of theblister17 can be removed from the exposed dermis and any exudate can be displaced in order to facilitate delivery of liquid withinreservoir11 when therotatable portion5 is further rotated to bring anoutlet port22 into registration with theaperture6.
In a further alternative embodiment illustrated in FIG. 57, a further modified[0353]rotatable portion82 has anoutlet port22 which is supplied with a controlled flow of liquid from areservoir83 via acapillary tube84. Amicro pump85 with associated electronic control circuitry is operable to impel liquid from the reservoir to theoutlet port22 via thetube84 and may be programmed to deliver metered quantities of liquid at predetermined time intervals or alternatively to supply a bolus quantity on demand.
The liquid supplied from the[0354]reservoir83 may be a drug or any other liquid which it is desirable to introduce onto the exposed de-epithelialised area ofskin8 when the outlet port is positioned in registration with anaperture6 of adevice1 as described in previous figures.
A similar arrangement is shown in FIG. 58 where[0355]micro pump85 is connected viacapillary tube84 to theoutlet port22. The pump in this embodiment however operates in a reverse direction to deliver liquid from theoutlet port22 to areceptor86 which may simply be a receptacle for capturing a sampled quantity of liquid or may alternatively comprise a sensor operable to carry out analysis on the sampled liquid. Theoutlet port22 may in this arrangement be regarded as a sampling port and, optionally, suction may be applied to a sampling chamber communicating with the sampling port in a manner described below in order to enhance the rate at which liquid may be collected. The micropump may itself be used to provide such suction.
A further embodiment is illustrated in FIG. 59 which corresponds broadly to the arrangement shown in FIG. 38 but includes a modification to the[0356]indicator38 which provides for automatic sensing of movement of the slug ofliquid37. In this embodiment anelectro optic sensor90 is supported by the clampingring39 upon thesuction tube15 and comprises alight source91 arranged to direct light through the tube so as to be received by alight sensor92. Theclamp39 may thereby be positioned at a location such that the slug of liquid is in registration with a suitable datum point on theindicator38 at the commencement of a blister forming period in which suction is applied, the electro optic sensor being positioned at a predetermined linear displacement along thetube15 so that movement of theslug37 by a predetermined distance will interrupt the transmission of light to thelight sensor92. An electronic circuit associated with thesensor90 may then be utilised to trigger an alarm so as to indicate to the user that formation of the blister has progressed to the required stage. Movement of the slug ofliquid37 by this predetermined amount thereby represents a predetermined volumetric displacement by the blister within thesuction cup9.
FIGS. 60, 61 and[0357]62 illustrate a preferred embodiment of thesyringe33 described above with reference to FIG. 38. Thesyringe33 comprises apiston34 which is axially slidable within acylinder35 in order to increase the volume of achamber100 defined within the cylinder, thereby creating suction on demand.
The[0358]piston34 is supported by an axially extendingpiston rod101 of cruciform cross section which is integrally moulded with a transversely extendinghandle102 and lockingarms103 and104 which project from the handle so as to extend externally along thecylinder35. The lockingarms103 and104 are formed so as to be resiliently biased towards one another thereby tending to close around thecylinder35.
The cylinder is provided with transversely projecting[0359]flanges105,106 which are offset by 90 degrees about the axis of the cylinder with respect to both theradially extending handle102 and the lockingarms103,104.
The locking[0360]arms103 and104 have respectivefree end portions107 and108defining grooves109 which indent the free end portions in an axial direction. The longitudinal extent of the lockingarms103 and104 is less than that of thepiston rod101. In use, a user grips thehandle102 and pulls the handle away fromflanges105,106 so as to retract thepiston34 along thecylinder35. When the displacement of thehandle102 is sufficient for thefree end portions107 and108 to be pulled clear of thecylinder35, thefree end portions107 and108 spring radially inwardly towards one another. Suction created within the cylinder by retraction of thehandle102 will result in thepiston34 and handle102 being biased against this direction of retraction so that by releasing the handle the piston will begin to travel in the return direction, this motion being arrested by engagement between thefree end portions107 and108 and alip110 defining the end of thecylinder35 such that the lip then extends into theslots105 as shown in FIG. 62.
Suction within the[0361]chamber100 is thereby communicated to the suction cup of thedevice1 by means of thesuction tube15 which is connected to anose portion111 of the syringe formed integrally with thecylinder35.
Since the locking[0362]arms103 and104 are resiliently biased into the locking position, thesyringe33 is in effect self locking and operates simply by manually retracting thehandle102. Although it would be possible for the user to release the suction by first withdrawing thehandle102 and splaying apart the lockingarms103 and104, this would require some co-ordinated manipulation of thehandle102,flanges105,106 and the lockingarms103,104 so it is most unlikely that any accidental release of the suction in this manner could occur. Thesyringe33 thereby provides a means operable to apply suction to thesuction chamber16 of thedevice1 which is simple to use, self locking and inherently resistant to accidental de-activation.
A further alternative embodiment of the present invention will now be described with reference to FIGS.[0363]63 to69 using corresponding reference numerals of previous Figures where appropriate for corresponding elements.
The[0364]device1 is modified in FIG. 63 to include apatch applicator120 which is operable to apply apatch121 to the area ofskin8 following de-epithelialisation while thedevice1 remains in situ.
The[0365]patch121 consists of a disc shapedcentral element122 which is to be reactively engagable with the de-epithelialised area ofskin8. Attached peripherally to thecentral element122 is a relativelyrigid support ring123 having on itsunderside124 anadhesive layer125.
A[0366]protective film126 overlays theunderside124 of thesupport ring123 and thecentral element122 thereby maintaining the efficacy of theadhesive layer125 prior to use and sealing thecentral element122.
The[0367]support ring123 is held in position by means ofpins134 which are mounted on therotatable portion5 and which pierce thesupport ring123. Anactuator127 is arranged so as to contact the support ring with thepins134 extending slidably through the actuator such that by movement of the actuator the support ring can be disengaged from the pins. Thepatch121 is received in apatch chamber128 defined by therotatable portion5 which in the initial position of the rotatable portion communicates with a co-operating recess129 formed in the upper surface of thebase3.
The[0368]actuator127 projects upwardly and clear of therotatable portion5 so as to be externally accessible to the user and is spring loaded into a raised position in which thepatch121 is suspended clear of thebase3.
In this initial position, the interface between the[0369]protective film126 and theadhesive layer125 is in alignment with the locus of movement of theblade18 between thebase3 androtatable portion5.
The[0370]actuator127 is reciprocatable in a direction towards and away from thebase3 so as to be operable to displacesupport ring123 and with it thepatch121 in a direction at right angles to the plane of thebase3.
The device of FIG. 63 has a[0371]base3 which defines anaperture6 which is of enlarged diameter sufficient to accommodate passage of thepatch121 and receives asuction cup9 having alip10 whose underside is coated withadhesive layer130. Anannular plug135 of resilient foam material is inserted between thesuction cup9 and the walls of theaccess port7 so as to retain the suction cup in coaxial relationship with the access port and retain the suction cup relative to thebase3 androtatable portion5 prior to use. Thelip10 comprises an outerannular region131 extending radially and at right angles to the cylindrical axis of thesuction chamber16 and further comprises an innerannular region132 which is frustoconical in shape. It should be noted that the degree of conicity of the inner annular region in FIG. 63 is exaggerated for clarity and that the axial extent to which the inner annular region projects is typically a fraction of 1 millimetre.
As shown in the underneath plan view of FIG. 64, the[0372]base3 is attachable to theskin4 of a user by means of anadhesive tape133. Acircular opening250 is provided in thetape133 to coincide with theaperture6 within which the skin site is to be accessed. An annular region251 surrounding theopening250 is provided with an acrylic adhesive coating so as to be impervious to body fluids and the remaining area of the tape receives a hydrocoloidal adhesive coating.
The[0373]suction cup9 and thebase3 are thereby independently securable to theskin4 by means of theadhesive layer130 and theadhesive tape133 respectively.
In use, the[0374]suction cup9 is used to form asuction blister17 as described above with reference to the device of FIG. 34. During the application of the device to the skin, theskin area8 will adhere to theadhesive layer130 and during the blister forming period theskin area8 will tend to remain raised within the innerannular region132 of thelip10 by suction.
The device is then actuated by rotation of the[0375]actuating ring46 as shown in FIG. 34 to moveblade18 through thesuction cup9 thereby severing both the cup and theblister17 and exposing a de-epithelialised area ofskin8 within theaperture6.
The[0376]actuating ring46 is further rotated to drive theblade18 through thepatch chamber128 so as to separate theprotective film126 from theadhesive layer125 as shown in FIG. 66. A thickenedblade18 of wedge shaped cross section may therefore be advantageously used in this embodiment in order to facilitate separation. The discardedprotective film126 is then allowed to fall into the recess129 where it remains. Theactuating ring46 is further rotated to engage and rotate therotatable portion5 of the device and to move thepatch chamber128 into registration with theaperture6 as shown in FIG. 67.
The[0377]actuator127 is then depressed so as to displace thepatch121 axially within thepatch chamber128 towards and into contact with the area ofskin8, the diameter of thecentral element122 being dimensioned so as to be slightly greater then thede-epithelialised area8 of skin exposed when the blister is disrupted.
In depressing the actuator[0378]127 as shown in FIG. 68, thesupport ring123 is dissociated from the attachment pins134 which remain stationary relative to therotatable portion5. Theactuator127 when subsequently retracted no longer carries with it thesupport ring123 and thepatch121 remains in situ in contact with the area ofskin8. Theadhesive tape133 is then dissociated from theskin4 and thebase3 dissociated from the skin so that the device can be lifted clear. Thepatch121 remains in situ as shown in FIG. 69 with thecentral element122 remaining in intimate contact with the de-epithelialised area ofskin8.
The[0379]patch121 may be a self contained means for administering a supply of drug and may for example comprise a porous pad impregnated with a liquid so that an active ingredient in the liquid is able to diffuse out of the pad and into the patient's bloodstream via the de-epithelialised area of dermis. Alternatively, thepatch121 may comprise a permeable membrane through which a liquid drug can be diffused from aconventional skin patch135 which as shown in FIG. 70 is applied over thepatch121 so as to adhere to the skin by means of a peripherally extendingadhesive layer136.
When used in this arrangement the[0380]skin patch121 may be regarded as an intervening patch which initially serves as a protective covering following exposure of the dermis and subsequently remains in an intervening position during a subsequent procedure. Theconventional skin patch135 although conventional in structure may contain drugs not normally associated with transdermal delivery but which can be successfully absorbed through a de-epithelialised dermis.
In the[0381]conventional skin patch135 theadhesive layer136 allows an active ingredient of apreparation137 to diffuse through the adhesive layer over its entire extent but absorption will in general be taken up primarily at the de-epithelialised site.
An alternative arrangement shown schematically in FIG. 71 uses a modified[0382]skin patch138 in which animpermeable barrier139 is adhered to the skin surrounding the de-epithelialised site byadhesive layer136, thebarrier layer139 having acentral aperture140 in registration with the interveningpatch121 through which the active ingredient of the preparation may diffuse.
The[0383]impermeable barrier layer139 forms part of anenclosure141 within which the preparation is packaged.
The above use of[0384]patch121 enables the newly formed de-epithelialised site to be covered prior to removal of thedevice1 thereby avoiding exposure of the dermis to atmosphere. This techniques also ensures that thepatch121 is automatically positioned accurately in alignment with the de-epithelialised site and in a manner which can be effected by a relatively unskilled user.
The[0385]device1 as described above and as modified in accordance with any of the alternative embodiments disclosed herein may therefore be used to form a de-epithelialised site which is subsequently overlaid by an implementing device used for implementing a required procedure such as transdermal delivery or sampling for diagnostic purposes. Examples of implementing devices already described include thereservoir11 of FIG. 34, thepatch121 of FIG. 69 and the modifiedskin patch138 of FIG. 71. Further examples of implementing devices will now be described using corresponding reference numerals throughout for corresponding elements where appropriate, it being understood that such implementing devices could be provided integrally within the device as shown in FIG. 34 or applied independently to a de-epithelialised site and including the possibility of use in conjunction with the interveningpatch121. A further option is to provide releasable connecting means operable between the device and each implementing device so that a number of implementing devices are interchangeable while the device is in use.
A further implementing[0386]device142 is shown schematically in FIG. 72 and simply consists of anenclosure141 defining anoutlet port22 and containing aporous slab143 in which a drug is contained in aqueous solution. The porosity of the slab is selected to have a rate limiting effect on the diffusion of drug out of the slab and into the dermis.
The[0387]slab143 may alternatively be a compressed mass of microspheres containing a drug. The microspheres may comprise biologically stable cross linked dextran or ceramics or may comprise bioerodible starch or other similar material. The slab may also be bounded by a bactericidal structure such as a mesh of fibrous silver bound material.
A further[0388]alternative implementing device144 shown schematically in FIG. 73 comprises anenclosure141 defining acell145 and having amembrane146 extending across theoutlet port22. Themembrane146 may be formed of a polymeric material having a rate limiting effect on diffusion of a preparation contained within the cell into the dermis. Themembrane146 may be bound with silver chloride as a bactericide. The diffused preparation may also include a vasodilating agent in order to increase blood flow locally in the exposed dermis and/or an anticoagulant to prevent formation of fibrin which could otherwise obstruct pores in the membrane.
The[0389]membrane146 may alternatively be a fibrous network of bound silver. Themembrane146 may be constructed as a fine mesh filter have a pore size of 0.2 to 2 microns for example in order to prevent the passage of bacteria into thecell145.
Since such implementing devices are likely to be in use for a number of days in registration with the de-epithelialised site, it will generally be desirable to provide some means of preventing bacterial contamination of the preparation contained within[0390]cell145. Where thecell145 contains a flowable material such as a liquid or gel, the material may be circulated through afilter147 as illustrated schematically in FIG. 74 where the filter is connected in series with apump148 bycapillary tube149. Both ends of thetube149 are connected to thecell145 such that by operation of the pump the preparation within the cell is circulated and filtered.Non-return valves150 are also incorporated in the circuit. The pump may be a simple displacement pump which in its simplest form can be a resilient tube with non-return valves positioned upstream and downstream of the tube so that repeated manual flattening of the tube will result in pumping action. Alternatively the pump may be an electronically operated micro pump such as a piezo electric membrane pump or peristaltic pump.
It may also be advantageous to provide for a flow of fluid through a[0391]space151 between themembrane146 and the dermis. As shown schematically in FIG. 75, inlet andoutlet tubes152 and153 respectively are connected to theenclosure141 for the inflow and outflow of fluid. In the example of FIG. 75, thetubes152 and153 are connected toreleasable connectors154 and155 of a standard luer connector type thereby enabling asupply156 of cleansing fluid to be connected to the inlet tube and a syringe orother suction device157 to be connected to the outlet tube. Cleansing fluid may thereby be periodically drawn through thespace151.
This cleansing operation may be required to remove excess exudate or to remove the products of enzymic reaction or other reactions between the exudate and the drug diffusing through the[0392]membrane146.
The apparatus of FIG. 75 may also be used for taking samples of exudate, or samples of substances extracted from the exudate using a filtering membrane for example, the contents of this[0393]syringe157 being available for subsequent analysis.
The apparatus of FIG. 75 may also be modified by removal of the[0394]membrane146 and without including any drug within thecell145 in circumstances where the de-epithelialised site is to be used only for sampling exudate and not for the transdermal delivery of any drug. In such an arrangement, the volume of thecell145 is preferably reduced to a minimum and may for example be provided by a groove formed in a block of material.
An alternative implementing[0395]device158 is shown schematically in FIG. 76 in which theenclosure141 receives a through flow of fluid from areservoir159 to a collectingchamber160. Checkvalves161 and162 are provided upstream and downstream of thecell145 respectively and adisplacement pump163 is operable to deliver metered quantities of fluid from the reservoir.
In this arrangement the volume of the[0396]cell145 is minimised and may be constituted by a capillary tube opening into a small space localised above the de-epithelialised dermis. Thereservoir159 and collectingchamber160 may be relatively small containers associated in structure with theenclosure141 or preferably may be larger containers connected remotely from theenclosure141 by respective tubes. Thepump163 may conveniently be a peristaltic pump.
The[0397]pump163 may be operated continuously or in intermittent bursts in order to provide a flow of fluid over a prolonged period, the fluid typically comprising a drug with an active ingredient which is transdermally absorbed. A particular advantage of this technique is that the products of any reaction between exudate from the dermis and the fluid are transported away to the collectingchamber160, as for example in the case of peptides where enzymic reaction from exudate is likely to occur.
A further advantage is that the drug concentration in the flowing fluid is less susceptible to depletion due to diffusion through the dermis so that the rate of diffusion can be accurately controlled.[0398]
An alternative implementing[0399]device159 shown schematically in FIG. 77 derives a continuous through flow of fluid fromreservoir159 via aflow restrictor164, thereservoir159 being provided with a pressurising means such that the contents of the reservoir are continuously pressurised and gradually are released through the flow restrictor so as to pass through thecell145 and into the collectingchamber160. The pressurising means165 may simply be a spring loaded actuating acting on a flexible bag type reservoir or may incorporate pressurised gas or a resilient bag to constantly maintain the contents of the reservoir under pressure.
A further[0400]alternative implementing device166 is shown schematically in FIG. 78. A continuous or intermittent flow of fluid is passed throughcell145 from asource167 to a collectingchamber160 which incorporates abio sensor168. An electronic output signal from thebio sensor167 is fed to acontrol unit169 which controls the actuation of thesource167 in its delivery of fluid, thesource167 being provided with both areservoir159 and apump163 for this purpose.
The[0401]bio sensor168 may be any one of a number of available bio sensors depending on the nature of the parameter which is to be controlled. The bio sensor may for example be an optical sensor responsive to light absorbed in passage through exudate extracted from thecell145, such a sensor being operable for example to measure glucose levels to give an indication of the glucose level in the patient's bloodstream, particularly where the administered drug is insulin.
It may be desirable to provide two separate[0402]de-epithelialised sites170 and171 as shown schematically in FIG. 79 used for sampling and drug delivery respectively. In this configuration,respective enclosures172 and173 provide sampling anddrug delivery cells174 and175 respectively arranged in registration with the skin sites.
Exudate collected in[0403]cell174 is delivered by apump176 to abio sensor168 which provides a measurement signal forcontrol unit169. Thecontrol unit169 actuates afurther pump177 to deliver metered quantities of drug to thecell175 from areservoir159.
The[0404]pump177 may for example be a micro pump of the type normally used in bubble jet ink printers and relying upon the pulsed application of heat to expel discrete quantities of liquid within capillaries by the formation of vapour bubbles.
Such a micro pump, in this case typically referred to as a thermal droplet generator, an array of nozzles is provided, each having an associated liquid channel of nanolitre volume with a heating element associated with each channel, the nozzle outlet dimensions being of the order of 40 microns diameter.[0405]
Activation of the nozzles can then be programmed using a suitable pulse generator and the system calibrated in terms of the number of pulses required to deliver a metered volume of drug.[0406]
Such an arrangement may for example be used to administer a quantity of drug and to monitor the level of a measurable parameter in the exudate in order to generate a feed back signal controlling the rate of delivery of the drug in order to stabilise the measured parameter at a required level. A control unit may also be programmed to activate the[0407]pump176 to sample the exudate at intervals which may be regular or dependent upon the sensed value.
It may also be desirable to utilise various means for enhancing or controlling the rate of delivery of a drug. In FIG. 80 for example a further[0408]alternative implementing device178 is shown schematically to comprise anenclosure141 provided with anelectric heating element179 which when actuated will heat the contents ofcell145 to a controlled temperature. The temperature of theheating element179 can be monitored simply by monitoring its electrical resistance or by means of a separate temperature sensing element. In the example of FIG. 80, thecell145 contains a quantity of drug mixed with a hydro gel which has a temperature dependent diffusivity. By controlling the electrical current passing through theheating element179 from an associated control circuit it is thereby possible to increase or decrease the rate at which drug is delivered to the de-epithelialised skin site.
A further[0409]alternative implementing device180 is shown schematically in FIG. 81 in which theenclosure141 is exposed to an alternating magnetic field provided by amagnetic circuit181 so as to apply an alternating magnetic field to the contents ofcell145. The contents ofcell145 are selected to be a mixture of permanent magnetic particles encapsulated in a polymeric material and porous polymeric particles in which a quantity of drug is absorbed. The rate at which drug diffuses out of the polymeric particles is dependent upon the degree of vibrational excitation induced by the magnetic field acting on the magnetic particles thereby allowing the rate of drug release to be controlled.
The release of a drug in a progressive and controlled manner may also be effected by incorporating the drug into a non-hydrated hydrogel polymer and introducing a quantity of water into contact with an outer surface of a bead of the gel, progressive hydration then occurring as a gradual process accompanied by a complimentary release of drug. As shown schematically in the example of FIG. 82, a bead of[0410]gel182 is placed withincell145 such that a surface of thegel183 is presented to the de-epithelialised skin site. A quantity ofwater184 is introduced into the remaining volume of thecell145 and is assimilated into the bead through anouter surface185 of the bead. As the water is assimilated into the bead, the volume of the bead increases and the liquid drug is expelled through thesurface183 so as to delivered to the dermis.
The technique of iontophoresis may also be utilised as shown schematically in FIG. 83 where an alternative implementing[0411]device186 incorporates afirst electrode187 withincell145 and a secondannular electrode188 which is placed peripherally of theenclosure141 and in contact with the skin peripheral to the de-epithelialised site. By applying a voltage of appropriate polarity between the first andsecond electrodes187 and188, ionised drug molecules can be urged in the direction of absorption through the dermis in order to enhance or control the rate of absorption. This apparatus may also be utilised in the reverse technique of enhancing the rate of production of certain exudates for sampling.
It may also be advantageous to pressurise a volume of[0412]liquid drug189 in contact with the de-epithelialised dermis in order to enhance the rate of drug absorption. Such pressure may for example be derived as shown in FIG. 51 by dividing the contents ofcell145 using animpermeable membrane190 to isolate thedrug189 from anosmotic system191. Theosmotic system191 comprises asemi-permeable membrane192 which separates a volume ofwater193 from a volume of a saturatedsalt194. Migration of water through the semi-permeable membrane results in an increased volume of the salt thereby exerting a pressure on theimpermeable membrane190 and pressurising the volume ofdrug189.
An alternative arrangement as shown in FIG. 85 in which a liquid drug is separated from a quantity of[0413]water193 by asemi-permeable membrane192. In this arrangement water diffuses into the liquid drug through the rate controlling membrane and an associated increase in pressure in the liquid enhances the rate of drug absorption through the de-epithelialised dermis.
A further alternative is shown in FIG. 86 which simply incorporates a charged[0414]polymer membrane195 intermediate the dermis and a liquid drug of a type in which the active ingredient comprises charged ions (for example a peptide or protein).
The inherent electric field provided in such a membrane interacts with the charged ions in a predetermined manner which can be selected to enhance diffusivity through the membrane for the purpose of absorption.[0415]
FIGS.[0416]87 to89 illustrate the manner in which a metered dose of liquid can be delivered to a de-epithelialised site using a metereddose dispenser200 connected via atube201 to anenclosure202 overlaying the de-epithelialised site.
The[0417]enclosure202 is provided with anoutlet tube203 connected to a flexible bagtype collecting chamber204.
The metered[0418]dose dispenser200 consists of acylinder205 defining areservoir chamber206 which is screw threaded to receive a threadedpiston207 which is manually rotatable by means of ahandle208. Areference arm209 projects from thecylinder205 parallel to the axis of thepiston207 so as to provide a reference against which the position of thehandle208 is alignable, the dimensions of thechamber206 and the screw pitch of the piston being selected such that metered units of volume are displaced from thereservoir chamber206 at each complete rotation of the handle.
The volume of the[0419]reservoir chamber206 will typically be in the range 0.3 to 0.5 millilitres.
A typical application of the metered[0420]dose dispenser200 would be for the delivery of a drug for pain relief, the drug being self administered by a patient at timed intervals or whenever required. The concentration of drug within theenclosure202 will tend to deplete with time as a result of absorption into the body via the de-epithelialised site and is replaced by actuation of thedispenser200 with a fresh volume of drug, the spent drug solution together with excess exudate from the site being displaced so as to be deposited in the collectingchamber204 via theoutlet tube203.
The[0421]enclosure202 may also be provided with avalved inlet port210 allowing a flushing solution to be injected into theenclosure202 from a syringe or other suitable source in order to periodically flush and cleanse the enclosure, excess flushing fluid and exudate being deposited in the collectingchamber204.
Apparatus described above with reference to the various embodiments of the invention may comprise components which have siliconised surfaces to minimise bacterial adhesion, particularly for those surfaces expected to come into contact with body fluids.[0422]
FIG. 90 shows a modification to the[0423]indicator38 shown in FIG. 38, the modified indicator now being described using corresponding references to previous Figures where appropriate for corresponding elements.
In FIG. 90, the[0424]suction tube15 is provided with a connecting side arm portion260 communicating with aliquid storage chamber261 provided by aliquid storage structure262.
The[0425]liquid storage structure262 is cylindrically formed from a deformable material having a shape memory such that it retains its cylindrical shape when internal and external pressures are equalised.
A suitable material for forming the structure is latex.[0426]
The apparatus shown in FIG. 38 would normally be supplied in the configuration shown in which liquid is contained within the[0427]liquid storage chamber261 without extending into thesuction tube15. This arrangement is advantageous over the configuration shown in FIGS. 38 and 59 where the slug of liquid could potentially become disrupted prior to use by impact and might for example be divided into two or more sections.
As shown in FIG. 91, the application of suction within the[0428]tube15 by retracting thepiston34 draws liquid from theliquid storage chamber261 into the tube, liquid being displaced from the chamber by a partial collapse of thestructure262 in response to the internal pressure being reduced by the effect of suction.
With the[0429]tube15 operatively connected to thesuction cup9 for a prolonged period, a suction blister will eventually form and the formation of the blister will displace a volume of air from within the suction cup, this displacement being transmitted through the tube so as to displace a slug ofliquid37 relative to its initial position, this displacement being detectable by operation of theindicator38. It will be apparent that the alternative indicator shown in FIG. 59 could equally well be operable in conjunction with such a side arm260 andstructure262.
In FIG. 92, the displaced slug of[0430]liquid37 has moved through a displacement indicative of a suction blister having fully formed thereby indicating to the user that the blister forming period is completed and that it is therefore time to commence the next stage of operation of the apparatus.
The[0431]liquid storage structure262 is located within arigid enclosure263 which prevents the structure being inadvertently compressed by handling while at the same time admitting ambient air pressure to the external surfaces of the structure.
FIGS.[0432]93 to98 illustrate the manner in which implementing devices may be interchangeably connected to a device in accordance with the present invention. In FIG. 93, an implementingdevice280 comprises areservoir281 defining afluid receiving chamber282 and having acannula283 which defines anoutlet284 communicating with the chamber.
The implementing[0433]device280 is in the form of adisc285 upon which thereservoir281 is mounted with thecannula283 projecting through the disk. FIG. 93 shows thedevice280 in its storage condition in which aclosure286 overlays thedisc285 and is partially penetrated by thecannula283 thereby closing theoutlet284.
A[0434]suction device287 is also mounted on thedisc285 and comprises asuction chamber288 in which apiston289 is retractable to create suction by rotation of a screw-threadedactuator290.
A[0435]second cannula291 communicating with the suction chamber also projects through thedisc285 into theclosure286.
In FIG. 94, the[0436]closure286 has been discarded immediately prior to use of the implementingdevice280, thereby exposing the first andsecond cannulas283,291.
A[0437]transdermal delivery device292 is shown partially in FIG. 96, omitted detail corresponding to that described above with reference to FIGS.34 to68 for example, and having abase3 defining anaperture6 through which a de-epithelialised skin site is prepared by forming and opening a suction blister as described above.
The[0438]base3 is secured adhesively toskin4 of a patient.
The[0439]transdermal delivery device292 has amovable portion293 which has anaccess port7 through which, in a first position of the movable portion relative to thebase3, the skin site is prepared and which, when moved into a second position as shown in FIG. 96, overlays theaperture6 and defines anopening294 communicating with the aperture and peripherally sealed by means of an O-ring seal295.
A first[0440]penetrable septum296 is located so as to be flush with anupper surface297 of themovable portion293 with aduct298 extending between the first septum and theopening294 whereby fluid may be introduced by penetration of the first septum in order to access theopening294.
A[0441]second septum299 is similarly provided and communicates via asecond duct300 with theopening294 to allow suction to be applied by penetrating the second septum to thereby draw fluid into the opening.
In FIG. 97, the implementing device is shown connected to the[0442]movable portion293 with the first andsecond cannulas283,291 penetrating the first andsecond septums296 and299 respectively. FIG. 98 illustrates the manner in which fluid within thefluid receiving chamber282 can be caused to flow into the opening in order to deliver fluid in contact with the de-epithelialised dermis, theactuator290 having been retracted to raise thepiston289 thereby creating suction at theopening294.
Liquid contained in the reservoir may thereby deliver transdermally and typically will comprise aqueous solution of a drug. During prolonged delivery, the[0443]actuator290 may be progressively retracted in order to refresh the liquid contained in theopening294 with further liquid drawn from the reservoir thereby maintaining a required concentration.
The implementing[0444]device280 may be disconnected from themovable portion293 simply by pulling them apart and if required, a further implementing device may be substituted. In this way, fresh doses of the drug may be administered or the drug may be varied either in concentration or in composition simply by interchanging implementing devices in which appropriate drugs are contained in the respective reservoirs. Alternatively, different types of implementing device as discussed above may be substituted for purposes other than the delivery of drugs.
The apparatus of FIGS.[0445]93 to98 may be modified to include a reservoir in which the walls of thefluid receiving chamber283 are collapsible.
A further[0446]alternative device301 will now be described with reference to FIGS.99 to111 using corresponding reference numerals to previous Figures where appropriate for corresponding elements.
The[0447]alternative device301 shown in plan view in FIG. 101 differs from thedevice1 of FIGS.34 to52 in the construction of therotatable portion5 but otherwise functions in the same way to apply suction to the skin, to form a suction blister and to remove the epithelial roof of the blister to thereby define a de-epithelialised erosion at the treatment site. In the FIGS.99 to111 thedevice301 in its various stages of operation is illustrated after the stage of forming the de-epithelialised erosion and removal from the device of thesuction tube15 with its associated components illustrated in FIG. 38.
The[0448]device301 includes a drug delivery reservoir having anoutlet port22 as shown in the underneath view of FIG. 99 and, formed in a separate compartment of the rotatable portion adjacent to the reservoir outlet port, asampling port302. By rotation of therotatable portion5 either thereservoir outlet port22 or thesampling port302 may be brought into registration with thebase aperture6 to access the de-epithelialised skin erosion so that thedevice301 may be used either for drug delivery or sampling respectively.
As shown in FIG. 99 the[0449]reservoir outlet port22 is provided with an O-ring seal24 and thesampling port302 is provided with an O-ring seal303. As shown in FIG. 102, the O-ring seal303 is operable between theupper surface23 of thebase3 and theunderneath surface304 of therotatable portion5, the O-ring seal being captively retained relative to the rotatable portion by a locating groove so as to be rotatable in registration with thesampling port302.
As shown in FIG. 103, the[0450]rotatable portion5 may be rotated into a position in which thesampling port302 overlays thede-epithelialised erosion305 in order to sample exudate generated at theskin erosion305 from the exposed dermis. In this configuration, as shown in FIG. 104, an air tight seal continues to be maintained between thebase3 and theskin4 by means of anadhesive layer306 which thereby provides an air tight seal. The O-ring seal303 maintains this air tight seal between thebase3 and therotatable portion5 so that thesampling port302 defines acylindrical sampling chamber307 into which exudate including plasma filtrate may fill.
A screw fitting[0451]308 is mounted on therotatable portion5 at the upper entrance to thesampling chamber307 thereby enabling a screw threadedsampling piston309 to be inserted into the sampling chamber and advanced or retracted to any desired axial position thereby enabling the volume of thesampling chamber307 to be variable. In FIG. 104 thesampling piston309 is shown in a fully advanced position in which the head of the piston is advanced into close proximity with theerosion305 and volume of thesampling chamber307 is thereby minimised. To initiate a sampling procedure, thesampling piston309 is initially inserted into thesampling port309 and advanced into the fully advanced position as shown in FIG. 104. Thesampling piston309 includes anaxially extending bore310 allowing air trapped within thesampling chamber307 to freely escape during the advancement of the sampling piston into the fully advanced position thereby avoiding any excess pressure in the sampling chamber which might otherwise have the undesirable effect of causing separation of thebase3 from the skin by disruption of theadhesive layer306.
An[0452]occlusive cap311 is then screw fitted to theouter end portion312 of the sampling piston so as to close thebore310 and constituting an openable closure. Thepiston310 is then retracted by screw action to a fully retracted position as shown in FIG. 105 thereby creating a partial vacuum in thesampling chamber307, typically in therange 100 to 200 millimetres of mercury below atmospheric pressure.
This position is maintained for a period of approximately 15 minutes during which time exudate accumulates in the[0453]sampling chamber307. The rate of production of exudate is enhanced by the partial vacuum created in the sampling chamber, the transdermal convective movement of liquid and entrained molecules from the plasma of the patient to the surface of the erosion being increased several fold. During this process, the intact semi-permeable capillary membrane of the dermis acts as a sieve to prevent significant contamination of the exudate liquid volume with red and white blood cells.
The[0454]occlusive cap311 is then released from its screw fitting with thepiston309 and detached, thereby allowing air to enter thebore310 and equalise pressure within thesampling chamber307 with atmospheric pressure. Acuvette313 as shown in FIGS. 107 and 108 is then fitted to theouter end portion312 of thesampling piston309 by means of a screw fitting314 as shown in FIG. 107, the cuvette defining acapillary slot315 which when fitted to the piston lies in communication with thebore310, the cuvette being formed of a transparent plastics material and having anabsorbent pad316 arranged to provide an air vent to anupper end317 of theslot315.
As shown in FIG. 109 the[0455]sampling piston309 may then be advanced into thesampling chamber307 so as to displace theexudate318 from thesampling chamber307 into thecuvette313 so as to fill theslot315, excess exudate being absorbed by thepad316.
The[0456]cuvette313 may then be detached by reverse screw action from thesampling piston309 and replaced by aplug319 as shown in FIG. 111 which is attachable by screw action to the sampling piston and includes apad320 of capillary active material for venting the sampling chamber to ambient air and collecting exudate continuing to emanate from theerosion305 and collected via thebore310.
The[0457]cuvette313 containing asample321 of the exudate as shown in FIG. 110 may then be inserted into an analysingapparatus322 such as a photometer.
The cuvette also contains a reagent located on a sidewall of the[0458]slot315 and selected to perform a chemical test on the sample. A range of reagents may be included in a single cuvette. The analysing apparatus may therefore be set up to respond to optically detectable changes in the reagent.
The[0459]alternative device301 may also be used for the delivery of a drug to theerosion305 by rotation of therotatable portion5 so as to bring theoutlet port22 of a drug reservoir within the rotatable portion into registration withaperture6 formed in thebase3 in a manner corresponding to the arrangement described above with reference to FIG. 36.
The alternative device may include other forms of openable closure, such as a valve mechanism.[0460]
The[0461]alternative device301 may be provided with a skin heating element as described above with reference to FIG. 55, the effect of heating being to enhance rates of sampling and delivery.
The sampling of exudate may alternatively be undertaken using a[0462]separate sampling device330 as shown in FIGS. 112 and 113. Thesampling device330 comprises acylindrical suction cup331 forming part of an enclosure having a partially flared peripheralannular flange332 having anadhesive layer333 which in use is presented to theskin334 of a patient at a location symmetrically surrounding ade-epithelialised skin erosion335, the erosion having been formed by any convenient method, but preferably using a suction blister forming device of the type described above for example with reference to FIG. 34. Thesuction cup331 is provided with anentrance grid324 or sieve to prevent the intrusion of tissue at the erosion. (Thegrid324 may optionally be omitted).
A[0463]capillary tube336 is connected to thesuction cup331 and defines acapillary bore337 communicating with asuction chamber338 defined by the suction cup.
The[0464]capillary tube336 is connected to asyringe339 operable to create a partial vacuum in thesuction chamber338 by retraction of apiston340, thesyringe339 being lockable at any position along its stroke so as to maintain any required level of partial vacuum.
A slug of[0465]liquid341 is located in thebore337 adjacent to a scale342 attached to thetube336 by aclamp343 and arranged so as to extend along the length of the bore.
The scale[0466]342 and the slug ofliquid341 thereby together comprise an indicator responsive to the volume of air displaced along the bore between the chamber and the syringe.
A[0467]side hole344 is formed in thesuction cup331 at a location adjacent to theflange332 and is normally closed by aresilient sleeve345 which externally overlays a cylindrical side wall portion of the suction cup.
In use, the flange is adhered to the skin as shown in FIG. 112 such that the[0468]erosion335 is open to the air within thesuction chamber338 and thepiston340 is retracted within thesyringe339 to create a partial vacuum within the suction chamber. The creation of this partial vacuum is accompanied by displacement of air from the chamber through thebore337 thereby causing the slug of liquid to move in a direction away from the suction cup. After a short period in which a relatively high level of partial vacuum is applied to thesuction chamber338 in order to remove any pockets of air lodged between the adhesive layer and the skin adjacent to the suction chamber, the piston is partially returned to an intermediate position at which a lower level of partial vacuum is applied to thesuction chamber338. The position of theclamp343 is adjusted that a zero of the scale342 coincides with the location of the slug ofliquid341. This level of partial vacuum is maintained for a period sufficient to accumulateexudate346 within thesuction chamber338 as shown in FIG. 113, the rate of transdermal production of exudate being enhanced by the presence of the partial vacuum such that typically a period of 30 minutes is sufficient to accumulate a volume of 100 to 300 microlitres using a partial vacuum of 200 mm mercury below atmospheric pressure.
Accumulation of exudate within the[0469]suction chamber338 is accompanied by progressive movement of the slug ofliquid341 as air is displaced from thesuction chamber338. The indicator comprising the scale342 may therefore be used to sense completion of the exudate collection phase. At the end of this phase, thepiston340 is returned to its rest position so that suction is no longer applied in thesuction chamber338.
A sample of exudate may then be taken by displacing the[0470]sleeve345 as shown in FIG. 113 to expose the outlet of theside hole344, amicrocuvette347 for example then being used to draw exudate through the side hole by capillary action. Themicrocuvette347 in this example consists of a transparent plastic slide having a capillary slot into which exudate liquid is drawn. Themicrocuvette347 is then inserted into an analyser such as a photometer in order to perform immediate analysis of the exudate.
The[0471]sampling device330 thereby provides a means of taking a sample of exudate from an erosion created by a de-epithelialising method, the sampling device being operable to enhance the rate at which exudate is collected by applying a partial vacuum over the erosion. This partial vacuum promotes a convection process by which exudate flows transdermally in response to a pressure differential through the semi-permeable membrane constituted by the exposed dermis. Moreover the dermis constitutes a sieve allowing plasma to pass and retaining blood cells. Relatively large molecules such as sugar and insulin are able to pass through the dermis thereby making it possible to perform analysis on the concentration of such constituents of the exudate as might for example be required in the treatment of diabetes.
The[0472]sampling device330 may be modified to include alternative indicators such as those described above with reference to FIGS. 59, 90,91 and92. Thesampling device330 may be further modified by creating a partial vacuum using a modified syringe having a screw threaded piston adjustor to allow continuous axial adjustment of the piston position or alternatively by the use of a micropump.
Throughout the description and claims the term perfusion should be understood to encompass both the partial and complete diffusion of a fluid through body tissue i.e. including the partial diffusion of a fluid in which certain molecules contained in the fluid are diffused through tissue leaving a residue of undiffused fluid.[0473]
