SPECIFICATIONIntravaginal deviceThis invention relates to intravaginal devices, particularly to such devices comprising a resilient cellular structure.
The prior art of contraceptive and therapeutic intravaginal devices is populated by devices having a variety of constructions and shapes and comprising various porous and non-porous materials. The present invention is in the field of intravaginal devices based on a cellular body and provides a device having a novel simple construction which combines simplicity of manufacture with ease of application and efficiency in use.
According to the present invention there is provided a device for intravaginal use comprising a resiliently compressible substantially cylindrical one-piece open-cellular polyurethane foam body having at its forward end a substantially centrally positioned surface depression, and having means to facilitate removal of the device from the vaginal cavity after use comprising a string attached at the base of the depression and extending through the body of the device and out from the end of the body remote from the depression, the dimensions of the body being such that when the device is inside the vaginal cavity the device is laterally compressed by the cavity wall so that it is retained in the cavity by sealing engagement of the cylindrical surface of the body with the cavity wall, and the dimensions of the surface depression being such that the wall of the depression is able to close resiliently on lateral compression to form a taper for ease of insertion and location of the device in the vaginal cavity and to shield the string attachment means at the base of the depression from contact with the vaginal cavity wall during and after insertion of the device in the cavity.
The cylindrical shape of the device body has the advantage of providing a large surface area for frictional retention of the device the vaginal cavity (passage or vault) and it facilitates correct insertion of the device into the cavity and retention of orientation for ease of removal of the device from the vaginal cavity after use. Moreover, a one-piece cylindrical shape can be produced simply by cutting from a block of the polyurethane foam and does not require production by moulding or special shaping.
The body of the device preferably has a high resilient compressibility so that a single size of device will be suitable for a wide range of vaginal cavity sizes. In fact only one size of device may be necessary for the normal range of vaginal cavity sizes, or perhaps two sizes of device for use before and after childbirth. Typically the cylindrical body may have a length of up to about 50 mm and a diameter of up to about 60 mm, an example of a suitable body being one having a length of 50 mm and a diameter of 50 mm.
The forward end of the cylindrical body, i.e. the end which is nearer to the cervix when the device is located inside the vaginal cavity, has a substantially centrally positioned surface depression (excavation or open cavity). The precise shape of the depression is not especially important provided that the desired tapering and shielding can be achieved. The depression may be for instance cuboid, conical, hemispherical or an intermediary thereof. Preferably the dimensions of the depression and the flexibility of the defining walls are such as to enable the walls to touch or almost touch when laterally compressed.
The ratio of the depth of the depression to the length of the cylindrical body may be in the range of for example 1:5 to 2:5. For instance, a 50 mm long cylinder may have a depression of depth in the range of 10 to 20 mm, e.g. 15 mm. The depression wall thickness, i.e. the difference between the cylinder diameter and the depression diameter, preferably is not less than 5 mm irrespective of the other dimensions of the device. The upper limit of the wall thickness depends on factors such as the compressibility of the foam and the desired taperability of the device. Examples of suitable wall thick- nesses at the cylinder end are from 5 to 10 mm.
A string to facilitate removal of the device from the vaginal cavity is attached at the base of the depression, preferably substantially centrally thereof. The string may be for example a cord or monofilament and preferably is of sterile soft material which will not irritate the vagina at possible points of contact. The string extends through the body of the device and out from the end of the body remote from the depression, preferably out from about the centre of that end, so that the string may be grasped and pulled to remove the device. If desired, at least the portion of the string extending from the device body may be in looped form to facilitate grasping and pulling. For instance the string may be a continuous piece of material or it may be a looped discontinuous piece of material the ends of which are attached at the base of the depression.One preferred string is a nylon (e.g.
Nylon 66) mono-filament since such a string is capable of maintaining an open loop for ease of removal of the device. The length of the exposed portion of the string between its exit from the device body and its furthest point may be for example about 25 to 30 mm.
Suitably the string is attached after the production of the depression. Means of attachment include heat-welding and adhesive compositions.
When an adhesive composition is employed preferably it is quick-setting. One example of a suitable adhesive composition is a rubber solution adhesive such as one based on a pale crepe natural rubber dissolved in a petroleum-based solvent.
Although, when an adhesive composition is employed as the attachment means, it should be selected bearing in mind the need to avoid adverse effects on the user of the device, the device of the present invention provides the advantage of shielding the adhesive or other attachment means from contact with the vagina walls owing to the position of attachment being inside the depression and therefore shielded by the walls of the depression, especially when the walls are compressed to a taper during insertion of the device. Thus the attachment of the string inside the depression enables a wider choice of adhesive composition or other attachment means than would be suitable for a more exposed position of attachment.
The polyurethane foam providing the body of the device preferably is soft and resilient and preferably has a porosity to allow permeation of air when inside the vaginal cavity in order to minimise undesirable odour. Also, when the device is employed as a contraceptive device, for which it is especially suitable, the porosity should provide a tortuous trap for spermatozoa so that no live spermatozoa can emerge from the depression end of the device. For contraception the device preferably contains a spermicide. Suitably the spermicide is introduced by impregnation into the preformed foam and accordingly the porosity parameters of the device should be such as to retain the spermicide therein. A similar consideration applies in respect of other medicaments desired for use in the device.
Suitable physical properties of the foam are a hardness in the range of for instance 0.4 to 2.5 kPa, preferably 0.4 to 1.0 kPa, when tested at 40% deflection according to BS 4443 Part 1(1979) Method 5A, a density of for instance 10 to 50 kg.m-3, preferably 12 to 20 kg.m-3, a resilient compressibility of at least 40% and a compression set of not greater than 15% and preferably less than 10% measured according to BS 4443 Part 1(1979) Method 6A.
The foam should be one which does not irritate or otherwise adversely affect the vagina. A preferred foam is a hydrophilic polyurethane foam.
Suitably the foam is a hydrophilic polyetherurethane foam. Preferably the polyurethane foam is one made by a one-shot process. A one-shot process is capable of producing a foam having the desired porosity and advantageous softness which are more difficult or impossible to produce by a prepolymer process.
The foam may be produced by reacting one or more polyether polyols, especially including a copolymer containing propylene oxide and ethylene oxide units, with a diisocyanate, e.g. tolylene diisocyanate, in the presence of a blowing agent and a catalyst and optionally one or more foam stabilisers and antioxidants. The polyol component preferably has an average hydroxyl functionality of about 3 and preferably the hydroxyl groups are primary groups. Suitably the major or sole polyol component has a molecular weight in the range 2,000 to 10,000, preferably 2,500 to 6,000. One or more subsidiary polyols having a lower molecular weight such as in the range 500 to 2,000 may be present.
Preferably the major or sole polyol component has a high ethylene oxide unit content of at least 40% and has terminal ethylene hydroxide groups.
As stated above, when a spermicide and/or other medicament is incorporated in the device, the spermicide and/or other medicament suitably is introduced by impregnation into the preformed foam. This technique enables a wider choice of spermicide and other medicaments than would be available for introduction prior to or during the process of production of the foam, especially if the foam is produced by an exothermic one-shot polyurethane-forming process. A spermicide commonly advocated for use in intravaginal contraceptive devices is nonoxynol-9, and that spermicide is also suitable for use in the device of the present invention.
For insertion into the vaginal cavity preferably the device is in a laterally precomposed state, for example under a compression of at least about 50%. Usually the device does not require moistening for insertion. The device is suitable for insertion into the cavity by means of a mechanical piston applicator such as a tubular applicator of the type employed to insert tampons. The applicator tube may have an internal diameter of for example 15 to 20 mm. The applicator may also serve as packaging for the device.
Owing to the ability of the device to conform to the varying shape of the vaginal cavity in sealing engagement with the cavity wall, as a result of the resilient compressibility and softness of the device, precise location of the device is not necessary for effective use. In particular it is not necessary for the device to close or even contact the os of the cervix.
An example of a preferred method for making the device is as follows:(i) producing a block of open-cellular polyurethane foam, preferably a hydrophilic polyurethane foam by a one-shot process;(ii) cutting the block into sheets of thickness the same as the desired length of the eventual devices;(iii) producing depressions of the desired dimensions in the surface of the sheet, suitably by profiling;(iv) cutting the desired cylindrical shapes at the positions of the depressions, suitably by stamping in a press, such that each depression is substantially centrally situated at a cylinder end;;(v) inserting a removal string centrally and longitudinally through each shape, e.g. by needlepunching from the depression end of each cylinder, such that the string extends from the base of the depression through the body of the cylinder and projects from the other end of the cylinder, preferably in looped form;(vi) anchoring the strings to the cylindrical bodies, for example by heat-welding or by applying a spot of an adhesive composition to the base of each depression at the position of the string;(vii) removing the cylindrical bodies from the sheet, e.g. by pulling the projecting length of each string;and preferably: :(viii) immediately encasing each body by forcing it through a tapered passage into a sterile tubular applicator, e.g. by pulling the projecting string length through the passage and applicator;(ix) closing the applicators, preferably including the incorporation of a piston for expelling the cylindrical body;(x) packaging the applicators.
A spermicide and/or other medicament may be incorporated by impregnation while the cut shapes are retained in the sheet.
It is found that production of the device by stamping or other cutting from a block of the foam produces a desirable surface for frictional retention of the device in the vaginal cavity and facilitates the introduction of spermicide and/or other medicaments by impregnation, in contrast to devices produced by moulding which tend to have smooth and relatively impervious surfaces.
The device does not include reinforcing inserts or impermeable diaphragms which would add to cost and the problem of compatibility and may reduce or prevent air circulation resulting in the risk of odour and possibly irritation or infection. Also the device does not require precision of location which is necessary for devices designed for abutting or fitting over the os of the cervix. Moreover, a single device of the present invention is capable of effective use in a wide range of vagina sizes.
One embodiment of the device is shown in the accompanying drawing which is a diagrammatic cross-section of the device in its normal uncompressed state. In the drawing, 1 is the device body, 2 2 is the depression, 3 is the withdrawal string and 4 is the point of attachment of the string at the base of the depression.