FIELD OF THE INVENTIONThe invention relates to topical compositions that provide dermatological benefit, such as for the treatment of inflammation, itching, pain relief, and/or other conditions associated with skin disorders.[0002]
BACKGROUND OF THE INVENTIONSevere dry skin disorders, known as ichthyosis, are often characterized by cracks, flakes, scales, redness, etc. Less severe, but more common, moderate to mild dry skin disorders are often characterized by less severe fissures, chaps, cracks, flakes, redness, etc. Such disorders can also include inflammation and be quite painful. Typically, such disorders are treated with topical oils, hydrating emollients, ointments, etc.[0003]
The topical use of alpha-hydroxy and beta-hydroxy acids, alpha-ketoacides, and esters thereof, is well known in the art to be effective as a preventative as well as a therapeutic treatment of dry skin disorders. Treatment is generally effective at acid concentrations of about 1% to about 20% by weight. Skin irritation caused by low pH levels may be ameliorated by neutralizing the acids with a base, such as ammonium hydroxide. See, for example, U.S. Pat. No. 4,105,783 (Yu et al.).[0004]
Further, it is believed that skin penetration by such compositions is enhanced using acid/base salts. See, for example, U.S. Pat. No. 4,888,354 (Chang et al.). In addition, the topical compositions may contain additional pharmaceutical and cosmetic additives, provided they do not adversely affect the formulation, stability, and activity of the acids and/or esters. Such additives include, for example, antimicrobials, antibiotics, neoplastic agents, cardiac drugs, antihistamines, anesthetics, antipsychotics, etc. See, for example, U.S. Pat. No. 4,888,354 (Chang et al.), U.S. Pat. No. 5,420,106 (Parab), and U.S. Pat. No. 5,705,168 (Parab).[0005]
There is still a need for compositions (e.g., lotions and creams) that can be used to reduce conditions associated with dry skin and other skin disorders, such as inflammation, itching, and/or pain relief.[0006]
SUMMARY OF THE INVENTIONOne aspect of the present invention combines dermatologically acceptable compositions (i.e., dermatological or dermatologic compositions) with one or more anesthetic and/or anti-inflammatory agents, preferably steroid anti-inflammatory agents. The compositions include at least one acid, amide, ester, or salt of an alpha-hydroxy acid, a beta- hydroxy acid, an alpha-keto acid, or combinations thereof (preferably at least one alpha-hydroxy acid, ester, amide, salt thereof, or combinations thereof). More preferably, the compositions include a combination of at least two salts, more preferably, at least one ammonium salt and at least one metal ion salt (preferably sodium or potassium salt) for enhanced penetration of the composition. Preferably, certain compositions include an anti-foaming agent.[0007]
A further aspect of the present invention is a composition including at least one alpha hydroxy acid, at least one ammonium salt of an alpha hydroxy acid, at least one potassium salt of an alpha hydroxy acid, and at least one sodium salt of an alpha hydroxy acid.[0008]
These compositions can also optionally include topical vehicles such as non-ionic surfactants, thickeners, emollients, humectants, and preservatives to provide preparations, such as lotions, creams, etc., for dry skin having enhanced preventative and therapeutic attributes.[0009]
The present invention provides methods for treating a subject, preferably a mammal, and more preferably a human, such as reducing inflammation of the skin, reducing itching and/or pain of the skin, and treating skin disorders that include contacting the skin with compounds containing any of the compositions of the present invention.[0010]
Another aspect of the present invention provides methods for preparing the dermatological compositions that include combining at least one acid, amide, ester, or salt of an alpha-hydroxy acid, beta-hydroxy acid, alpha-keto acid, or combinations thereof (preferably at least one alpha-hydroxy acid, ester, amide, salt thereof, or combinations thereof), with one or more anesthetic agents and/or one or more anti-inflammatory agents. Preferably, such methods also include adding one or more ammonium salts and/or one or more metal ion salts. A preferred method of preparing certain dermatological compositions of the present invention includes providing an alpha-hydroxy acid and neutralizing at least a portion of it with ammonium hydroxide in an aqueous solution to provide a neutralized acid solution that preferably may be combined with at least one anti-inflammatory agent and/or at least one anesthetic agent.[0011]
A further method of preparing a dermatologic composition of the present invention includes combining at least one alpha-hydroxy acid, beta-hydroxy acid, or alpha-keto acid, or combinations thereof, with at least one ammonium salt of an alpha-hydroxy acid, beta-hydroxy acid, or alpha-keto acid, or combinations thereof, at least one sodium salt of an alpha hydroxy acid, beta-hydroxy acid, or alpha-keto acid, or combinations thereof, and at least one potassium salt of an alpha hydroxy acid, beta-hydroxy acid, or alpha-keto acid, or combinations thereof. Preferably, the method includes combining at least one alpha-hydroxy acid, beta-hydroxy acid, or alpha-keto acid, or combinations thereof, with at least two of the above ammonium, sodium, and potassium salts.[0012]
High concentrations, such as from about 10% to about 30% by weight, of alpha-hydroxy acids in a skin preparation, when neutralized to yield the ammonium salts, have been found to develop an unpleasant odor and occasionally may result in yellow coloration over time. Thus, the present invention also provides a method for preparing such compositions using activated charcoal for deodorizing. Compositions of the invention may be contacted with activated charcoal. Thereafter, the charcoal may be separated from the composition. Compositions that may be contacted with the activated charcoal may include compositions that have been neutralized with ammonium hydroxide. Deodorizing is defined as removing or significantly reducing a fragrance by neutralization or adsorption. Odor-free is defined as a fragrance completely or substantially eliminated from a composition.[0013]
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTIONThe invention concerns dermatological compositions that can be in the form of dermatologically acceptable lotions and creams, for example. The compositions of the present invention can be used to treat one or more skin disorders, such as dry skin, ichthyosis, inflammation, and irritation. Certain preferred compositions can be used to reduce the amount of inflammation of the skin of a human. Certain other preferred compositions can be used to reduce the amount of itching and/or pain of the skin of a human. Certain other preferred compositions include a combinations of salts that enhance skin penetration of the active ingredients of the compositions.[0014]
Acids, Amides, Esters, Salts[0015]
The dermatological compositions include at least one active ingredient selected from an acid, amide, ester, or salt. Preferably, such active ingredients are racemic mixtures and, preferably, are selected from the group of an alpha-hydroxy acid, a beta-hydroxy acid, an alpha-keto acid, an ester thereof, an amide thereof, a salt thereof, and combinations thereof. More preferably, such active ingredients are selected from the group of an alpha-hydroxy acid, an amide thereof, an ester thereof, a salt thereof, and combinations thereof. Certain preferred embodiments include a combination of at least one alpha-hydroxy acid and at least one salt thereof. Preferably the salt is an ammonium salt, a metal ion salt (e.g., a potassium salt or a sodium salt), or a combination thereof. More preferably, a combination of such salts is used. Even more preferably, at least two different salts are used. Most preferably, a combination of an ammonium salt, a potassium salt, and a sodium salt is used.[0016]
Examples of such acids, amides, esters, or salts include citric acid, glycolic acid, glucuronic acid, galacturonic acid, alpha-hydroxybutyric acid, alpha-hydroxyisobutyric acid, beta-hydroxybutyric acid, lactic acid, malic acid, mandelic acid, mucic acid, pyruvic acid, saccharic acid, tartaric acid, tartronic acid, maleic acid, beta-phenyllactic acid, beta-phenylpyruvic acid, glucuronolactone, gluconolactone, methyl pyruvate, ethyl pyruvate, salts thereof, and combinations thereof.[0017]
A preferred set of such active ingredients includes the alpha-hydroxy acids. Alpha-hydroxy acids are aliphatic mono- and di-carboxylic acids including, but not limited to, citric acid, glycolic acid, glucuronic acid, galacturonic acid, alpha-hydroxybutyric acid, alpha-hydroxyisobutyric acid, lactic acid, malic acid, mandelic acid, mucic acid, pyruvic acid, saccharic acid, tartaric acid, tartronic acid, and the like. Preferred alpha-hydroxy acids of the present invention are those of the formula (I): R—CH(OH)—COOH, wherein R is an alkyl group or a hydrogen. Preferably, R is a C[0018]1to C5alkyl group including, for example, methyl, ethyl, propyl, butyl, or pentyl as well as branched groups thereof. Preferred acids include lactic, glycolic, and malic acids. Most preferred is lactic acid.
Typically, the compositions include both an acid and a salt thereof, as for example, an alpha-hydroxy acid and an ammonium salt thereof. The alpha-hydroxy acids and a base, such as ammonium hydroxide, are typically reacted in an aqueous solution to provide a neutralized acid solution. Generally, at least a portion of the acid is neutralized. Thus, as used herein, a “neutralized” acid solution or combination of acids in solution is defined as an acid solution in which at least a portion of the acid is neutralized to provide the salt of the acid or acids. The neutralized acid solution, formed when an acid is reacted with an ammonium-containing base, such as ammonium hydroxide, can be generally free of unreacted ammonia (herein “unreacted ammonia” refers to dissolved ammonium ions). This may occur when a stoichiometrically lesser amount of the base is added to the acid. A neutralized acid solution, as defined herein, may also include solutions in which unreacted ammonia is present.[0019]
The compositions preferably include one or more acids, amides, esters, or salts present in a total amount (e.g., acid plus salt) of at least about 1% by weight, more preferably at least about 5% by weight, and even more preferably at least about 8% by weight, based on the total weight of the composition (e.g., lotion, cream, etc.). Additionally, the one or more acids, amides, esters, or salts are present in the compositions in a total amount no greater than about 50% by weight, more preferably, no greater than about to about 40% by weight, and even more preferably no greater than about 15%, based on the total weight of the composition. Typically, one or more acids, in the form of a free acid, in combination with one or more salts are present in the compositions. Preferably, the total amount of one or more free acids is at least about 1% by weight, and more preferably, at least about 10% by weight, based on the total weight of the composition. Preferably, the total amount of one or more free acids is no greater than about 30% by weight, more preferably, no greater than about 20% by weight, and most preferably no greater than about 15% by weight, based on the total weight of the composition. Preferably, the total amount of one or more salts is at least about 1% by weight, and more preferably, at least about 5% by weight, based on the total weight of the composition. Preferably, the total amount of one or more salts is no greater than about 40% by weight, and more preferably, no greater than about 30% by weight, based on the total weight of the composition. The pH of the compositions of the present invention are preferably at least about 3, and more preferably at least about 4.5, and preferably no greater than about 6, and more preferably no greater than about 5.5.[0020]
In certain preferred embodiments, the compositions include a combination of one or more ammonium salts, one or more potassium salts, and one or more sodium salts. Even more preferably, the compositions include a combination of 2 or more salts. In such compositions, preferably, the total amount of ammonium salts, if present, (preferably, of one or more alpha-hydroxy acids) is at least about 1% by weight, and more preferably, at least about 5% by weight, based on the total weight of the composition. Preferably, the total amount of ammonium salts, if present, (preferably, of one or more alpha-hydroxy acids) is no greater than about 40% by weight, and more preferably, no greater than about 30% by weight, based on the total weight of the composition. Most preferably, the ammonium salt is ammonium lactate and, if present, is present in an amount of, preferably at least about 10% and more preferably at least about 15.9%, and preferably no greater than about 29.6%, even more preferably no greater than about 15%, based on the total weight of the composition. In such compositions, preferably, the total amount of potassium salts, if present, (preferably, of one or more alpha-hydroxy acids) is at least about 1% by weight, and more preferably, at least about 5% by weight, based on the total weight of the composition. Preferably, the total amount of potassium salts, if present, (preferably, of one or more alpha-hydroxy acids) is no greater than about 30% by weight, and more preferably, no greater than about 20% by weight, based on the total weight of the composition. Most preferably, the potassium salt is potassium lactate and, if present, is present in an amount of at least about 3% and no greater than about 7%, based on the total weight of the composition. In such compositions, preferably, the total amount of sodium salts, if present, (preferably, of one or more alpha-hydroxy acids) is at least about 1% by weight, and more preferably, at least about 5% by weight, based on the total weight of the composition. Preferably, the total amount of sodium salts, if present, (preferably, of one or more alpha-hydroxy acids) is no greater than about 30% by weight, and more preferably, no greater than about 20% by weight, based on the total weight of the composition. Most preferably, the sodium salt is preferably sodium lactate and, if present, is present in an amount of about 3% and no greater than about 7%, based on the total weight of the composition.[0021]
Anesthetic Agents and/or Anti-inflammatory Agents[0022]
Certain preferred compositions may additionally include one or more anesthetic agents and/or anti-inflammatory agents to provide enhanced therapeutic benefits to the skin preparation. Typically, an anti-inflammatory agent will reduce, and preferably, eliminate, inflammation of the skin of a subject when the composition is applied topically. Typically, an anesthetic agent will reduce, and preferably, eliminate, itching and/or pain of the skin of a subject when the composition is applied topically. Various combinations of such agents can be used for desired effect.[0023]
Anesthetic agents that can be used in the present invention include topical local anesthetics, such as anesthetics that can be used topically on the skin or can be injected as a local anesthetic. Examples of such topical local anesthetic agents include, but are not limited to, pramoxine HCl, benzocaine, benzyl alcohol, dibucaine HCl, dyclonine HCl, lidocaine, tetracaine, and tetracaine HCl. Combinations of such agents can be used. A preferred anesthetic agent is pramoxine HCl.[0024]
Preferably, the total amount of one or more anesthetic agents, if present, is at least about 0.5% and more preferably at least about 0.75%, based on the total weight of the composition. Preferably, the total amount of one or more anesthetic agent is no greater than about 20%, and more preferably, no greater than about 5%, based on the total weight of the composition.[0025]
Anti-inflammatory agents that can be used in the present invention include steroids (i.e., corticosteroids). Examples of such agents include, but are not limited to, hydrocortisone acetate, betamethasone dipropionate, amcinonide, betamethasone valerate, fluocinolone acetonide, triamcinolone acetonide, clocortolone pivalate, and dexamethasone. Combinations of such agents can be used. A preferred steroid for use in the present invention is hydrocortisone acetate.[0026]
Preferably, the total amount of one or more anti-inflammatory agents, if present, is at least about 0.01%, and more preferably, at least about 0.05% by weight, based on the total weight of the composition. Preferably, the total amount of one or more anti-inflammatory agent is no greater than about 2.5%, and more preferably, no greater than about 1.5% by weight, based on the total weight of the composition.[0027]
Anti-Foaming Agents[0028]
Anti-foaming agents, or foam depressants, are optionally added to the compositions of the present invention to prevent undesirable creaming upon application of the composition when rubbed into the skin. “Creaming” is understood by those skilled in the art to occur when a composition rubbed into the skin forms a white layer on the skin before penetration. The more vigorously the composition is rubbed, the whiter the composition becomes. It has been discovered that by adding an anti-foaming agent to a dermatological composition, creaming is substantially eliminated. Although not caused exclusively by anesthetic agents, creaming may occur when one or more topical anesthetic agents, particularly pramoxine HCl, is present in the composition. Pramoxine HCl is a desirable anesthetic agent as compared with other anesthetics, such as lidocaine and benzocaine, because many people have allergies to these other anesthetics. Pramoxine HCl does not cause the same topical sensitivity as compared to these other anesthetics, it is effective at minimal concentrations, and has a duration of action longer than that of other anesthetics (see, for example, Fisher, A. F.; “The Safety of Pramoxine Hydrochloride When Used as a Topical (Surface) Anesthetic,”[0029]Cutis,62:122-123 (1998); Fisher, A. A.; “Allergic Reactions to Topical (Surface) Anesthetics with Reference to the Safety of Tronothane,”Cutis,25:584 (1980); and Schmidt, J. L., Blockus, L. E., Richards, R. K., “The Pharmacology of Pramoxine Hydrochloride: A New Topical Anesthetic,”Anesth. Analg.,32:418 (1953)), but it does have the undesirable side-effect of causing creaming upon application to the skin when used in the compositions of the present invention. This problem is solved by including an anti-foaming agent in the compositions of the present invention.
Acceptable anti-foaming agents of the present invention include silicone-based oils, preferably dimethylsiloxane polymers, and copolyol waxes. Such dimethylsiloxane polymers are commercially available under the trade designations DIMETHICONE 250, DIMETHICONE 350, DIMETHICONE 450, CYCLOMETHICONE, and DIMETHICONE, all from Dow Corning, Midland, Mich. A particularly preferred anti-foaming agent is DIMETHICONE 350 dimethylsiloxane polymer. Combinations of such agents can be used. Effective concentrations of DIMETHICONE 350 from Dow Corning, Midland, Mich., or other anti-foaming agents in the compositions of the present invention, if present, are at least about 0.25% by weight, more preferably at least about 0.5% by weight, and most preferably at least about 0.8% by weight. Preferably, the compositions include no greater than about 3% by weight, more preferably no greater than about 2% by weight, and most preferably no greater than about to about 1.2% by weight.[0030]
Non-Ionic Surfactants[0031]
Non-ionic surfactants are present in preferred formulations to aid in providing an emulsion of the composition. Selection of surfactant and concentration of the surfactant will have a significant effect on the overall “feel” of the composition. Also, a greater stability of the composition may be gained through the blending of multiple non-ionic surfactants than may be achieved through the use of any single surfactant. Preferred non-ionic surfactants that may be used in the compositions of the present invention include glyceryl stearate, PEG 100-stearate, polyoxyl-20-cetostearyl ether, glyceryl monooleate, glyceryl palmitostearate, self-emulsifying wax, polyoxyl-20-stearate, polyoxyl-40-stearate, polyoxyl-60-stearate, polyoxyl-80-stearate, polyoxyl-20-oleate, polyoxyl-40-oleate, polyoxyl-60-oleate, polyoxyl-80-oleate, polyoxyl-20-palmitate, polyoxyl-40-palmitate, polyoxyl-60-palmitate, polyoxyl-80-palmitate, laureth-2, laureth-4, laureth-6, and laureth-8. More preferred non-ionic surfactants include emulsifying wax, such as POLAWAX (available from Croda, Parsippany, N.J.), laureth-4, and polyoxyl-40-stearate. A most preferred non-ionic surfactant is self-emulsifying wax.[0032]
Combinations of such agents can be used such as a combination is glyceryl stearate and PEG-100 stearate. A preferred non-ionic surfactant of the present invention includes a system of glyceryl stearate, PEG-100 stearate, polyoxyl-40-stearate, and laureth-4. Glyceryl stearate and PEG-100 stearate are supplied pre-blended by Uniqema (formerly ICI Americas, New Castle Del.). Effective concentrations of the pre-blended glyceryl stearate and PEG- 100 stearate in the compositions of the present invention are at least about 2.0% by weight, and more preferably at least about 2.75% by weight, based on the total weight of the composition. Preferably, compositions of the present invention contain no greater than about 5.5% by weight, and more preferably no greater than about to about 5.25% by weight, based on the total weight of the composition. Polyoxyl-40-stearate is selected because the stearates tend to enhance composition stability in comparison to the oleates and palmitates. Polyoxyl-40-stearate is available in cosmetic grade from Uniqema (New Castle, Del.). Effective concentrations of polyoxyl-40-stearate in the compositions of the present invention are preferably at least about 0.5% by weight, and more preferably at least about 0.75% by weight, based on total weight of the composition. Preferably, effective concentrations of polyoxyl-40-stearate in the compositions of the present invention are no greater than about 5 % by weight, and more preferably no greater than about 1.25% by weight, based on total weight of the composition. Effective concentrations of laureth-4 in the compositions of the present invention are preferably at least about 0.5% by weight, and more preferably at least about 1.25% by weight, based on total weight of the composition. Effective concentrations of laureth-4 in the compositions of the present invention are preferably no greater than about 3%, and more preferably no greater than about 1.75% by weight, based on total weight of the composition. Effective concentrations of emulsifying wax in preferred compositions of the present invention are preferably at least about 2% and preferably no greater than about 10%, based on the total weight of the composition.[0033]
Thickeners[0034]
Although the non-ionic surfactants impart a certain amount of thickening to the compositions of the present invention, it is difficult to find the correct balance of surfactants and concentrations thereof that will impart the desired stability to the composition. Therefore, thickeners, also known in the art as viscosity modifiers, are preferably used to adjust the composition to the desired consistency without affecting the stability imparted by the non-ionic surfactant system. Acceptable thickeners that may be used in the compositions of the present invention include methyl cellulose, hydroxypropyl methyl cellulose, ethyl cellulose, cetyl alcohol, cetostearyl alcohol, stearyl alcohol, magnesium aluminum silicate, xanthan gum, aluminum magnesium silicate, tribeneonite, kaolin, magnesium trisilicate, monemorillonite, saeonite, stearic acid, and talc. Combinations of such agents can be used.[0035]
A preferable thickener of the present invention includes a system of methyl cellulose, cetyl alcohol, and magnesium aluminum silicate. Magnesium aluminum silicate is particularly preferred element of the thickener system as it acts as both an emulsion stabilizer as well as a viscosity modifier. It also imparts to the composition a smooth, silky, slippery feel without affecting the stability of the composition contributed by the non-ionic surfactant system and does not interfere with the creaming prevention of the anti-foaming agent. Effective concentrations of methyl cellulose in the compositions of the present invention are preferably at least about 0.0001% by weight, and more preferably at least about 0.0005% by weight, based on total weight of the composition. Effective concentrations of methyl cellulose in the compositions of the present invention are preferably no greater than about 1% by weight, and more preferably no greater than about 0.5% by weight, based on total weight of the composition. Effective concentrations of cetyl alcohol in the compositions of the present invention are preferably at least about 0.2% by weight, and more preferably at least about 0.5% by weight, based on total weight of the composition. Effective concentrations of cetyl alcohol in the compositions of the present invention are preferably no greater than about 5% by weight, and more preferably no greater than about 3.25% by weight, based on total weight of the composition. Effective concentrations of magnesium aluminum silicate in the compositions of the present invention are preferably at least about 0.5% by weight, more preferably at least about 1% by weight, and most preferably at least about 1.25% by weight, based on total weight of the composition. Effective concentrations of magnesium aluminum silicate in the compositions of the present invention are preferably no greater than about 10% by weight, more preferably no greater than about 5% by weight, and most preferably no greater than about 1.75% by weight, based on total weight of the composition.[0036]
An additional preferred thickener of compositions of the present invention includes stearic acid. In these preferred compositions thickened using stearic acid, the stearic acid is preferably present in an amount of at least about 1% and no greater than about 5%, based on total weight of the composition.[0037]
Emollients and Humectants[0038]
Emollients and humectants soften the skin and stabilize and control the moisture content of a dermatological composition. Preferred emollients that may be used in the compositions of the present invention include glycerin 99.5%, glycerin 95%, glycerin 85%, cetyl alcohol, light mineral oil, medium mineral oil, and heavy mineral oil. Preferred humectants that may be used in the compositions of the present invention include glycerin 99.5%, glycerin 95%, glycerin 85%, propylene glycol, and butylene glycol. Combinations of such agents can be used.[0039]
More preferable emollients and humectants of the present invention include glycerin 99.5%, propylene glycol, and light mineral oil. Glycerin 99.5% and propylene glycol, when used together, typically act synergistically to aid in stabilizing compositions of the present invention. Further, propylene glycol enhances penetration of the skin by compositions at concentrations of 5% by weight or more, based on total weight of the composition. Conversely, butylene glycol used alone is not a penetration enhancer, but does work synergistically with glycerin 99.5% to enhance penetration. Effective concentrations of glycerin 99.5% in the compositions of the present invention are preferably at least about 1% by weight, more preferably at least about 3% by weight, and even more preferably at least about 3.75% by weight, based on total weight of the composition. Effective concentrations of glycerin 99.5% in the compositions of the present invention are preferably no greater than about 10% by weight, more preferably no greater than about 6% by weight, and even more preferably no greater than about 4.25% by weight, based on total weight of the composition. Effective concentrations of propylene glycol in the compositions of the present invention are preferably at least about 1% by weight, and more preferably at least about 3% by weight, based on total weight of the composition. Effective concentrations of propylene glycol in the compositions of the present invention are preferably no greater than about 15% by weight, and more preferably no greater than about 10% by weight, based on total weight of the composition.[0040]
Light mineral oil is preferable as an emollient as it imparts less of a greasy feel to the composition, giving it a lighter feel than do the heavier oils. Effective concentrations of light mineral oil in the compositions of the present invention are preferably at least about 1% by weight, more preferably at least about 3% by weight, even more preferably at least about 4% by weight, and most preferably at least about 5% by weight, based on total weight of the composition. Effective concentrations of light mineral oil in the compositions of the present invention are preferably no greater than about 20% by weight, more preferably no greater than about 15% by weight, and most preferably no greater than about 12% by weight, based on total weight of the composition.[0041]
Preservatives[0042]
Preservatives prolong the useful life of the composition by killing bacteria, yeasts, and molds which may impair the effectiveness of the compositions of the present invention. Preferable preservatives that may be used in the compositions of the present invention include methylparaben, ethylparaben, propylparaben, propylparaben potassium salt, propylparaben sodium salt, and butylparaben. Combinations of such agents can be used. More preferable preservatives of the present invention include methylparaben and propylparaben. Methyl and propylparaben attack water-bourne microbes, and when used together, their effectiveness is greater than each used alone. Effective concentrations of methylparaben in the compositions of the present invention are preferably at least about 0.02% by weight, and more preferably at least about 0.1% by weight, based on total weight of the composition. Effective concentrations of methylparaben in the compositions of the present invention are preferably no greater than about 1% by weight, more preferably no more than about 0.3% by weight, and even more preferably no greater than about 0.2% by weight, based on total weight of the composition. Effective concentrations of propylparaben in the compositions of the present invention are preferably at least about 0.01% by weight, more preferably at least about 0.025% by weight, and even more preferably at least about 0.1%, based on total weight of the composition. Effective concentrations of propylparaben in the compositions of the present invention are preferably no greater than about 1% by weight, more preferably no greater than about 0.6% by weight, and even more preferably no greater than about 0.075% by weight, based on total weight of the composition.[0043]
Fragrance[0044]
If desired, a component may be added to the composition to impart a fragrance. Fragrances may be used to add a pleasing scent to a generally unscented composition or, alternatively, may be used to assist in concealing the odor of a composition having a strong and/or unpleasant scent. Fragrance components, if included in a preferred composition, are preferably present in the compositions in an amount of no greater than about 1% by weight, based on the total weight of the composition.[0045]
Water, preferably purified water, is typically and preferably used in the compositions of the invention. Water may be used in any amount required to prepare the compositions of the invention, but is typically present in an amount of at least about 30% and typically no greater than about 60% by weight, based on the total weight of the composition.[0046]
Methods of Preparation[0047]
An acid/acid salt solution is made by mixing a selected alpha-hydroxy, beta-hydroxy, alpha-keto acid, an ester, amide, or salt thereof, an ammonium salt, a metal ion salt, or a combination of any of the above, with purified water or by neutralizing an acid with a stoichiometrically lesser amount of base, such as ammonium hydroxide, to form the “neutralized” acid/acid salt solution. Alternatively, a commercially available salt, such as an ammonium lactate solution (available from PURAC America, Lincolnshire, Ill., or Pfanstiehl Labs, Inc., Waukegan, Ill.) may be combined with an acid to form an acid/acid salt solution.[0048]
A Gum Phase composition is preferably prepared by mixing a thickener and, optionally, fillers, into hot, purified water, mixing until uniform at a temperature of about 80° C. to about 85° C. A Water Phase composition is preferably prepared using hot purified water, optionally including emulsifiers, humectants, lubricants, thickeners, and antimicrobial agents. The Gum Phase is typically transferred to the Water Phase and mixed, maintaining a temperature of about 80° C. to about 85° C. An Oil Phase composition is preferably prepared by mixing mineral oil with, optionally, one or more of a surfactant, a lubricant, an emulsifier, a foam stabilizer and an emollient. The Oil Phase is typically heated to about 80° C. to about 85° C. An Active Phase composition is preferably prepared by dissolving and mixing one or more of an anesthetic agent and/or an anti-inflammatory agent with purified water.[0049]
The Oil Phase is typically added to the Water Phase, mixed, and cooled. To this, preferably, the acid/acid salt composition is added, with mixing, and to this the Active Phase is preferably added, with continued mixing. The pH of the resulting composition is adjusted to the desired level using either base or acid, and any desired optional agents, such as anesthetics or anti-inflammatory agents, are then added to the composition, as disclosed in the Examples.[0050]
Deodorized Compositions[0051]
One of the problems associated with neutralizing the alpha-hydroxy acid with ammonium hydroxide is that in the reaction product, free or unreacted ammonia is present. In dermatological preparations, such as lotions and creams, that contain low concentrations of reactive product, the unreacted ammonia is not often noticeable nor objectionable. At higher concentrations of the reactive product, however, such as neutralized alpha-hydroxy acid greater than 10% by weight, unreacted ammonia from the dermatological preparations can give off a strong, unpleasant ammonia odor. Currently available products having a high percentage of unreacted ammonia employ fragrances to mask the unpleasant odor of ammonia. A disadvantage to the use of fragrances to mask the odor is that many patients who require treatment with high concentrations of alpha-hydroxy acids are at the same time allergic to such fragrances and may experience irritation and stinging. Often the diseased skin becomes abraded or broken. Use of fragrances in products applied to the skin may result in unpleasant side effects. A further problem associated with high concentrations of the neutralized alpha-hydroxy acids is that the preparations occasionally develop a yellow coloration over time.[0052]
In order to prepare a deodorized composition of the present invention, the alpha-hydroxy acid is combined with ammonium hydroxide, to provide a neutralized acid solution containing unreacted ammonia. Before combining the neutralized acid solution, containing unreacted ammonia, with the selected anesthetic and/or anti-inflammatory agents or other ingredients, the reaction product is contacted with activated carbon. The activated carbon purifies, decolorizes, and removes odor from the composition by absorbing unreacted ammonia, and other impurities that may be present in the composition, onto the surface of the carbon particles. The deactivated carbon has an extremely large surface area per unit weight making it an efficient absorptive material. The ‘activation’ of carbon in its manufacture produces many pores within the carbon particles. It is the vast area of the walls within these pores that accounts for most of the total surface area of the carbon.[0053]
Activated carbon adsorption is a time-release phenomenon that takes place in three steps. Initially, impurities in solution contact the external surface of a carbon particle as the liquid passes through the carbon bed. Secondly, impurities diffuse into the pores of the carbon particle. Finally, impurities are attracted to the pore wall and held by electrostatic (physical) or chemical forces. The adsorption method required to deodorize the compositions of the present invention is dependent on contact time with the carbon, unreacted ammonia concentration, impurity concentration, and adsorption affinity.[0054]
Deodorizing methods of the present invention preferably include passing the neutralized solution, containing unreacted ammonia, through an activated carbon cartridge to provide a deodorized filtrate. The filtrate is then typically combined with one or more anesthetic agents described above and/or one or more anti-inflammatory agents described above, providing a composition for use in dermatological formulations.[0055]
Methods of the present invention alternatively include forming a slurry of activated carbon particles and neutralized acid solution containing unreacted ammonia, which is then filtered to provide the deodorized composition of the present invention. A preferred method for large scale commercial preparation involves adding activated carbon to the neutralized solution to form a slurry which is stirred prior to filtering. The amount of activated carbon necessary in the method of the present invention may vary from about 30% to about 75% by weight of the total aqueous solution of the neutralized alpha-hydroxy acid. The slurry of the activated carbon and neutralized acid is stirred at ambient temperatures for about 15 minutes to about 2 hours. Following this treatment, the carbon is filtered off and the deodorized filtrate is combined with the selected anesthetic and/or anti-inflammatory agents.[0056]
Optional Additives[0057]
The resulting composition is used to prepare dermatological formulations in the form of, for example, creams and lotions, in accordance with well known procedures. Such formulations are well known to those of skill in the art. Examples of additives, as indicated above, which may be used in formulating creams include, but are not limited to, petrolatum, non-ionic surfactants, mineral oil, long-chain alcohols, and fatty acids. Examples of additives used in formulating lotions include, but are not limited to, propylene glycol and non-ionic surfactants.[0058]