Abstract:
The present invention provides a method for stimulating hair growth in a mammalian species or converting vellus hair or intermediate hair to terminal hair or stimulating hair follicles to increase hair growth and one or more properties selected from the group consisting of luster, sheen, brilliance, gloss, glow, shine or patina of hair associated with the follicles or increasing one or more of: length, thickness, number, and density, of eyelash hair or eyebrow hair comprising applying to the skin of a patient a composition comprising an effective amount of an EP 3  agonist or an EP 4  agonist prodrug or a mixture thereof. Such compositions which are used in treating the skin or scalp of a human or non-human animal may comprise an effective amount of 3, 7 or 3 and 7 thia prostanoic acid. A mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester is preferred for this treatment.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/435,126, filed Jan. 21, 2011, the disclosure of which is hereby incorporated in its entirety herein by reference. 
     FIELD OF THE INVENTION 
     This invention relates to a method for stimulating the growth of mammalian hair comprising the application to mammalian skin of a 3, 7 or 3 and 7 thia or oxa prostanoic acid derivative or a pharmacologically acceptable salt thereof, alone, or in association with a topical pharmaceutical carrier. 
     BACKGROUND OF THE INVENTION 
     Dermatologists recognize many different types of hair loss, the most common by far being “alopecia” wherein human males begin losing scalp hair at the temples and on the crown of the head as they get older. While this type of hair loss is largely confined to males, hence its common name “male pattern baldness,” it is not unknown in women. No known cure has yet been found despite continuing attempts to discover one. 
     A good deal is known about various types of human hair and its growth patterns on various parts of the body. 
     For purposes of the present invention, it is necessary to consider various types of hair, including, terminal hairs and vellus hairs and modified terminal hairs, such as seen in eye lashes and eye brows. Terminal hairs are coarse, pigmented, long hairs in which the bulb of the hair follicle is seated deep in the dermis. Vellus hairs, on the other hand, are fine, thin, non-pigmented short hairs in which the hair bulb is located superficially in the dermis. As alopecia progresses, a transition takes place in the area of approaching baldness wherein the hairs themselves are changing from the terminal to the vellus type. 
     Another factor that contributes to the end result is a change in the cycle of hair growth. All hair, both human and animal, passes through a life cycle that includes three phases, namely, the anagen phase, the catagen phase and the telogen phase. The anagen phase is the period of active hair growth and, insofar as scalp hair is concerned, this generally lasts from 3-5 years. The catagen phase is a short transitional phase between the anagen and telogen phases which, in the case of scalp hair, lasts only 1-2 weeks. The final phase is the telogen phase which, for all practical purposes, can be denominated a “resting phase” where all growth ceases and the hair eventually is shed preparatory to the follicle commencing to grow a new one. Scalp hair in the telogen phase is also relatively short-lived, some 3-4 months elapsing before the hair is shed and a new one begins to grow. 
     Under normal hair growth conditions on the scalp, approximately 88% of the hairs are in the anagen phase, only 1% in catagen and the remainder in telogen. With the onset of male pattern baldness, a successively greater proportion of the hairs are in the telogen phase with correspondingly fewer in the active growth anagen phase. 
     Alopecia is associated with the severe diminution of hair follicles. A bald human subject will average only about 306 follicles per square centimeter, whereas, a non-bald human in the same age group will have an average of 460 follicles per square centimeter. This amounts to a one-third reduction in hair follicles which, when added to the increased proportion of vellus hair follicles and the increased number of hair follicles in the telogen phase, is both significant and noticeable. Approximately 50% of the hairs must be shed to produce visible thinning of scalp hair. It is thus a combination of these factors: transition of hairs from terminal to vellus, increased number of telogen hairs—some of which have been shed, and loss of hair follicles that produces “baldness”. 
     While a good deal is known about the results of male pattern baldness, very little is known about its cause. The cause is generally believed to be genetic and hormonal in origin although, the known prior art attempts to control it through hormone adjustment have been singularly unsuccessful. 
     One known treatment for male pattern alopecia is hair transplantation. Plugs of skin containing hair are transplanted from areas of the scalp where hair is growing to bald areas with reasonable success; however, the procedure is a costly one in addition to being time-consuming and quite painful. Furthermore, the solution is inadequate from the standpoint that it becomes a practical, if not an economic, impossibility to replace but a tiny fraction of the hair present in a normal healthy head of hair. 
     Other non-drug related approaches to the problem include such things as ultra-violet radiation, massage, psychiatric treatment and exercise therapy. None of these, however, has been generally accepted as being effective. Even such things as revascularization surgery and acupuncture have shown little, if any, promise. 
     By far, the most common approach to the problem of discovering a remedy for hair loss and male pattern alopecia has been one of drug therapy. Many types of drugs ranging from vitamins to hormones have been tried and only recently has there been any indication whatsoever of even moderate success. For instance, it was felt for a long time that since an androgenic hormone was necessary for the development of male pattern baldness, that either systemic or topical application of an antiandrogenic hormone would provide the necessary inhibiting action to keep the baldness from occurring. The theory was promising but the results were, for the most part, disappointing. 
     The androgenic hormone testosterone was known, for example, to stimulate hair growth when applied topically to the deltoid area as well as when injected into the beard and pubic regions. Even oral administration was found to result in an increased hair growth in the beard and pubic areas as well as upon the trunk and extremities. While topical application to the arm causes increased hair growth, it is ineffective on the scalp and some thinning may even result. Heavy doses of testosterone have even been known to cause male pattern alopecia. 
     Certain therapeutic agents have been known to induce hair growth in extensive areas of the trunk, limbs and even occasionally on the face. Such hair is of intermediate status in that it is coarser than vellus but not as coarse as terminal hair. The hair is generally quite short with a length of 3 cm. being about maximum. Once the patient ceases taking the drug, the hair reverts to whatever is normal for the particular site after six months to a year has elapsed. An example of such a drug is diphenylhydantoin which is an anticonvulsant drug widely used to control epileptic seizures. Hypertrichosis is frequently observed in epileptic children some two or three months after starting the drug and first becomes noticeable on the extensor aspects of the limbs and later on the trunk and face. (The same pattern of hypertrichosis is sometimes caused by injury to the head.) As for the hair, it is often shed when the drug is discontinued but may, in some circumstances, remain. 
     Streptomycin is another drug that has been found to produce hypertrichosis, in much the same way as diphenylhydantoin, when administered to children suffering from tuberculous meningitis. About the same effects were observed and the onset and reversal of the hypertrichosis in relation to the period of treatment with the antibiotic leave little question but that it was the causative agent. 
     Two treatments have been demonstrated as showing some promise in reversing male pattern alopecia. These treatments include the use of a microemulsion cream containing both estradiol and oxandrolone as its active ingredients and the use of organic silicon. 
     In addition to the foregoing, it has been reported in U.S. Pat. Nos. 4,139,619 and 4,968,812 that the compound minoxidil is useful for the treatment of male pattern baldness. That compound, among others, has proven to have considerable therapeutic value in the treatment of severe hypertension. It is a so-called “vasodilator” which, as the name implies, functions to dilate the peripheral vascular system. Dermatologists and others have recognized that prolonged vasodilation of certain areas of the human body other than the scalp sometimes result in increased hair growth even in the absence of any vasodilating therapeutic agent. For instance, increased hair growth around surgical scars is not uncommon. Similarly, arteriovenous fistula have been known to result in increased vascularity accompanied by enhanced hair growth. Externally-induced vasodilation of the skin, such as, for example, by repeated biting of the limbs by the mentally retarded and localized stimulation of the shoulders by water carries has been known to bring on hypertrichosis in the affected areas. Be that as it may, similar techniques such as continued periodic massage of the scalp have been found to be totally ineffective as a means for restoring lost hair growth to the scalp. Scar tissue on the scalp inhibits rather than promotes hair growth. 
     Bimatoprost, which is sold by Allergan, Inc. of Irvine, Calif., U.S.A. as LATISSE® ophthalmic solution, has been found to be effective to increase the growth of eyelashes. 
     It is, therefore, a principal object of the present invention to provide a novel and effective treatment for the stimulation of hair growth and the treatment of male pattern baldness. 
     Another object of the invention is to provide a method of stimulating hair growth in humans and non-human animals that is compatible with various types of therapeutic agents or carriers and, therefore, would appear to be combinable with those which, by themselves, demonstrate some therapeutic activity such as, for example, microemulsion creams or topical compositions containing estradiol and oxandrolone, minoxidil or agents that block the conversion of testosterone to dihydrotesterone (Procipia). 
     Still another objective is the provision of a treatment for the stimulation of hair growth which, while effective for its intended purpose, is apparently non-toxic and relatively free of unwanted side effects. 
     An additional object of the invention herein disclosed and claimed is to provide a method for treating hair loss in men or women which can be applied by the patient under medical supervision no more stringent than that demanded for other topically-administered therapeutic agents. 
     Other objects of the invention are to provide a treatment for male pattern alopecia which is safe, simple, painless, cosmetic in the sense of being invisible, easy to apply and quite inexpensive when compared with hair transplants and the like. 
     U.S. Pat. Nos. 6,410,591; 6,538,018: 6,767,920 and 6,956,057 disclose various 3, 7 or 3 and 7 thia or oxa protanoic acid derivatives as agents for lowering intraocular pressure (IOP) are hereby incorporated by reference in their entireties. U.S. Pat. No. 6,956,057 also discloses that EP 4  agonists other than the 3, 7 or 3 and 7 thia or oxa protanoic acid derivatives disclosed in said patents lower IOP. 
     SUMMARY OF THE INVENTION 
     In the discussion of this invention the following terms have the following meanings: 
     An “EP 4  agonist prodrug” is an inactive precursor of an EP 4  agonist drug that is converted into its active form in the body by normal metabolic processes. Preferably, the prodrug is an ester of an EP 4  agonist, more preferably an alkyl ester, e.g. a lower alkyl ester of PGE. 
     An “EP 4  agonist” is a compound that binds to the EP 4  receptor of a cell and triggers a response by that cell that mimics the action of the naturally occurring endogenous substance that is PGE. 
     An “EP 3  agonist” is a compound that binds to the EP 3  receptor of a cell and triggers a response by that cell that mimics the action of the naturally occurring endogenous substance that is PGE. 
     “Pharmaceutically acceptable salts” refer to those salts which retain the biological effectiveness and properties of the free acid and which are obtained by reaction with inorganic bases such as sodium hydroxide, potassium hydroxide or calcium hydroxide and the like or organic bases such as lysine, arginine, ethanolamine and the like. 
     “Alkyl” refers to a straight-chain, branched or cyclic saturated aliphatic hydrocarbon. Preferably, the alkyl group has 1 to 12 carbons. More preferably, it is a lower alkyl of from 1 to 7 carbons, most preferably 1 to 4 carbons. Typical alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, pentyl, hexyl and the like. The alkyl group may be optionally substituted with one or more substituents are selected from the group consisting of hydroxyl, cyano, alkoxy, ═O, ═S, NO 2 , halogen, dimethyl amino, and SH. 
     “Alkenyl” refers to a straight-chain, branched or cyclic unsaturated hydrocarbon group containing at least one carbon-carbon double bond. Preferably, the alkenyl group has 1 to 12 carbons. More preferably it is a lower alkenyl of from 1 to 7 carbons, most preferably 1 to 4 carbons. The alkenyl group may be optionally substituted with one or more substituents selected from the group consisting of hydroxyl, cyano, alkoxy, ═O, ═S, NO 2 , halogen, dimethyl amino, and SH. 
     “Alkoxyl” refers to an “O-alkyl” group. 
     “Aryl” refers to an aromatic group which has at least one ring having a conjugated pi electron system and includes carbocyclic aryl, heterocyclic aryl and biaryl groups. The aryl group may be optionally substituted with one or more substituents selected from the group consisting of halogen, trihalomethyl, hydroxyl, SH, OH, NO 2 , amine, thioether, cyano, alkoxy, alkyl, and amino 
     “Alkaryl” refers to an alkyl that is covalently joined to an aryl group. Preferably, the alkyl is a lower alkyl. 
     “Effective amount” is defined as an amount which is effective in growing hair. 
     “Hydrocarbyl” refers to a hydrocarbon radical having only carbon and hydrogen atoms. Preferably, the hydrocarbyl radical has from 1 to 20 carbon atoms, more preferably from 1 to 12 carbon atoms and most preferably from 1 to 7 carbon atoms. 
     “Substituted hydrocarbyl” refers to a hydrocarbyl radical wherein one or more, but not all, of the hydrogen and/or the carbon atoms are replaced by a halogen, nitrogen, oxygen, sulfur or phosphorus atom or a radical including a halogen, nitrogen, oxygen, sulfur or phosphorus atom, e.g. fluoro, chloro, cyano, nitro, hydroxyl, phosphate, thiol, etc. 
     “Amide” refers to —C(O)—NH—R′, wherein R′ is alkyl, aryl, alkylaryl or hydrogen. 
     “Amine” refers to a —N(R″)R′″ group, wherein R″ and R″′ are independently selected from the group consisting of alkyl, aryl, and alkylaryl. 
     “Thioether” refers to —S—R″, wherein R″ is alkyl, aryl, or alkylaryl. 
     This invention provides pharmaceutical compositions for topical application to enhance hair growth comprising an effective amount of a 3, 7 or 3 and 7 thia or oxa protanoic 
                                
acid derivatives represented by the formula I:
 
     wherein hatched lines represent the a configuration, a triangle represents the 13 configuration and a dotted line represents the presence or absence of a double bond; 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2  or 
     
       
                 
         
             
             
         
      
     
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , phenyl, or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, in association with a pharmaceutical carrier adapted for topical application to mammalian skin. 
     A preferred group of the compounds of the present invention includes compounds that have the following structural formula II: 
     
       
                 
         
             
             
         
      
     
     Another preferred group includes compounds having the formula III: 
     
       
                 
         
             
             
         
      
     
     In the above formulae, the substituents and symbols are as hereinabove defined. 
     In the above formulae: 
     Preferably, A and B are both S. 
     Preferably, D represents a covalent bond or is CH 2 ; more preferably D is CH 2 . 
     Preferably Z represents a covalent bond. 
     Preferably R is H. 
     Preferably R 1  is H. 
     Preferably Y is O. 
     Preferably X is CO 2 R and more preferably R is selected from the group consisting of H, methyl and i-propyl. 
     Another aspect of the invention provides methods for stimulating the rate of hair growth and for stimulating the conversion of vellus hair or intermediate hair to growth as terminal hair in a human or non-human animal by administering to the skin of the animal an effective amount of a 3, 7 or 3 and 7 thia or oxa prostanoic acid derivatives represented by the formula I: 
                                
wherein hatched lines represent the a configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2  or 
     
       
                 
         
             
             
         
      
     
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , phenyl, or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl, or substituted derivatives thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, in association with a pharmaceutical carrier adapted for topical application to mammalian skin. 
     Some other embodiments of the invention are included in the following paragraphs: 
     1. The method of treating or preventing alopecia caused by chemotherapy which comprises applying to a patient in need thereof an effective amount of a 3, 7 or 3 and 7 thia or oxa prostanoic acid compound represented by the formula I as a foam produced from a foamable liquid composition, wherein said composition comprises one or more of said compounds of formula I, a surfactant, wherein the surfactant optionally includes a foam stabilizer and an aqueous-alcohol solvent, comprising water and an alcohol, which enables said compound to be solubilized.
 
2. A foamable liquid composition, for use in the method of paragraph 1, comprising one or more of the a 3, 7 or 3 and 7 thia or oxa prostanoic acid compound represented by the formula I and a surfactant, wherein the surfactant optionally includes a foam stabilizer and an aqueous-alcohol solvent, comprising water and an alcohol, which enables said active ingredient to be solubilized.
 
3. The composition of paragraph 2 wherein said aqueous-alcohol solvent further comprises an acid and a water soluble solvent, wherein said acid is an inorganic acid, or an organic acid containing eight carbons or less and said water soluble solvent is selected from the group consisting of butylene glycol, glycerin, polyglycerin, ethylene glycol, and propylene glycol.
 
4. The composition of paragraph 3 wherein said alcohol is selected from the group consisting of methanol, ethanol, propanol and mixtures thereof
 
5. The composition of paragraph 4 wherein said acid is lactic acid and said water soluble solvent is propylene glycol.
 
6. The composition of paragraph 5 wherein said lactic acid is provided at a concentration of from 0.5 to 5 percent, by weight, of the foamable liquid composition and said propylene glycol is provided in an amount of from 1 to 20 percent, by weight, of the foamable liquid composition
 
7. The composition of paragraph 6 wherein said alcohol is ethanol and is provided in an amount of from 1 to 50 percent, by weight, of the foamable liquid composition.
 
8. The composition of paragraph 7 wherein said surfactant is oleth-20 and is provided in an amount of from 0.1 to 5 percent, by weight, of the foamable liquid composition.
 
9. The composition of paragraph 8 wherein said foam stabilizer is lauryl glucoside and is provided in an amount of from 0.05 to 0.5 percent, by weight, of the foamable liquid composition.
 
10. A gel comprising a 3, 7 or 3 and 7 thia or oxa prostanoic acid compound represented by the formula I
 
                                
wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, in a pharmaceutically-acceptable solvent, comprising propylene glycol and alcohol and a crosslinked acrylic polymer thickening agent such as a Carbomer, e.g. Carbomer 934P, wherein the crosslinked acrylic polymer thickening agent is neutralized with a neutralizing agent such as diisopropanolamine. 
     11. A composition in the form of a gel comprising from 0.01% to 10% of a 3, 7 or 3 and 7 thia or oxa prostanoic acid compound represented by the formula I 
                                
wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, in association with a pharmaceutical carrier adapted for topical application to mammalian skin, by weight, a crosslinked copolymer of acrylic acid as a thickening agent, and a pharmaceutically acceptable solvent. 
     12. The composition of paragraph 11, wherein said pharmaceutically acceptable solvent is selected from the group consisting of ethanol, propanol, butanol, propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, PEG-200, PEG-400, glycerol and mixtures thereof
 
13. The composition of paragraph 12, comprising a solvent selected from the group consisting of ethanol, propanol and butanol.
 
14. The composition of paragraph 13, comprising a solvent selected from the group consisting of ethanol and isopropanol.
 
15. The composition of paragraph 14, comprising a solvent selected from the group consisting of propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, PEG-200, PEG-400, and glycerol.
 
16. A composition of paragraph 15, wherein said solvent comprises a mixture comprising a first solvent selected from the group consisting of ethanol, propanol and butanol and a second solvent selected from the group consisting of propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, PEG-200, PEG-400, and glycerol.
 
17. The composition of paragraph 16, wherein said solvent comprises a mixture of ethanol and propylene glycol.
 
18. The composition of paragraph 17, further comprising a neutralizing agent.
 
19. The composition of paragraph 18, wherein said neutralizing agent is selected from the group consisting of ammonium hydroxide, arginine, 2-amino-2-methyl-1-propanol, dimethanolamine, dibutanolamine, diisobutanolamine, tributanolamine, triisobutanolamine, tri-sec-butanolamine, tripropylamine, ethanolamine, diethanolamine, triethanolamine, PEG-15 cocamine, diisopropanolamine, methylethanolamine, diisopropylamine, dipropylenetriamine, tromethamine, isopropylamine ethylene diamine, triisopropanolamine, tetrahydroxypropyl ethylenediamine, trimethamine, 2-aminobutanol, aminoethyl propanediol, aminomethyl propanediol, aminomethyl propanol, sodium hydroxide, and potassium hydroxide.
 
20. The composition of paragraph 19, wherein said neutralizing agent is selected from the group consisting of 2-amino-2-methyl-1-propanol, diisopropanolamine, triisopropanolamine, and tetrahydroxypropyl ethylenediamine.
 
21. The composition of paragraph 20, wherein said neutralizing agent is 2-amino-2-methyl-1-propanol.
 
22. The composition of paragraph 11, wherein said solvent is present in said composition in an amount of at least about 20%.
 
23. The composition of paragraph 22 which comprises from about 20% to about 99%, by weight, of said solvent.
 
24. The composition of paragraph 11, wherein said crosslinked copolymer of acrylic acid comprises an acrylate/C 10-30  alkyl acrylate crosspolymer.
 
25. The composition of paragraph 24 wherein said solvent is present in said composition in an amount of at least about 20%.
 
26. A composition in the form of a gel comprising: from about 0.1 to 10% a 3, 7 or 3 and 7
 
                                
thia or oxa prostanoic acid compound represented by the formula I:
 
wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, from about 30% to about 80% of a first solvent selected from the group consisting of propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, PEG-200, PEG-400, and glycerol; from about 10% to about 50% a second solvent selected from the group consisting of ethanol, propanol and butanol; from about 0.01% to about 50% of a crosslinked copolymer of acrylic acid; from about 0% to about 3% of a neutralizing agent; and water. 
     27. A method for stimulating hair growth in a human comprising applying to human skin an effective amount of a 3, 7 or 3 and 7 thia or oxa prostanoic acid compound represented by the formula I 
                                
wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, in association with a pharmaceutical carrier adapted for topical application to mammalian skin. 
     28. The method of paragraph 27 wherein Y is O. 
     29. The method of paragraph 27 wherein the concentration of the compound applied is from about 0.0000001% to about 50% by weight of the pharmaceutical carrier. 
     30. The method of paragraph 27 wherein the compound is selected from the group consisting of: 
     
         
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-(hydroxy)-5-(naphthyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid methyl ester; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-(hydroxy)-5-(naphthyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-(hydroxy)-5-(naphthyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid isopropyl ester; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzothienyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid methyl ester; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzothienyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzothienyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid isopropyl ester; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzofuranyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid methyl ester; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzofuranyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid; and 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzofuranyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid isopropyl ester.
 
31. The method of paragraph 27 wherein the compound is 3,7-dithia PGE1-isopropyl ester.
 
32. The method of paragraph 27 wherein the hair is eyelashes.
 
33. The method of paragraph 27 wherein the compound is applied to the eyelids.
 
34. The method of paragraph 33 wherein the compound is applied to the eyelid margins.
 
35. The method of paragraph 27 wherein the compound is applied to the eyebrows.
 
36. The method of paragraph 27 wherein the compound is applied to the scalp.
 
37. A method of increasing one or more of length, thickness, number, and density, of eyelash hair or eyebrow hair, comprising administering an effective amount of a 3, 7 or 3 and 7 thia or oxa protanoic acid compound represented by the formula I
 
       
    
     
       
                 
         
             
             
         
      
     
     wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond; 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or substituted derivatives thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, in association with a pharmaceutical carrier adapted for topical application to mammalian skin, to a person on the area where hair growth is desired. 
     38. The method of paragraph 37 wherein Y is O. 
     39. The method of paragraph 37 wherein the composition is administered to an eyelid margin or to an eyebrow. 
     40. The method of claim  37  wherein the compound is selected from the group consisting of: 
     
         
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-(hydroxy)-5-(naphthyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid methyl ester; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-(hydroxy)-5-(naphthyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-(hydroxy)-5-(naphthyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid isopropyl ester; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzothienyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid methyl ester; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzothienyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzothienyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid isopropyl ester; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzofuranyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid methyl ester; 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzofuranyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid; and 
         {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzofuranyl)pent-1-enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid isopropyl ester.
 
41. The method of paragraph 37 wherein the compound is 3,7-dithia PGE1-isopropyl ester.
 
42. The method of paragraph 37 wherein the hair is eyelashes.
 
43. The method of paragraph 37 wherein the compound is applied to the eyelids.
 
44. The method of paragraph 43 wherein the compound is applied to the eyelid margins.
 
45. The method of paragraph 37 wherein the compound is applied to the eyebrows.
 
46. The method of paragraph 37 wherein the compound is applied once a day.
 
47. A method for stimulating hair growth in a mammalian species or converting vellus hair or intermediate hair to terminal hair or stimulating hair follicles to increase hair growth and one or more properties selected from the group consisting of luster, sheen, brilliance, gloss, glow, shine or patina of hair associated with the follicles or increasing one or more of length, thickness, number, and density, of eyelash hair or eyebrow hair comprising applying to the skin of a patient an effective amount of an EP 3  agonist or an EP 4  agonist prodrug or a mixture thereof
 
48. The method of paragraph 47 comprising applying to the skin of a patient an effective amount of a 1 to 1 mixture of an EP 3  agonist and an EP 4  agonist prodrug.
 
49. A method of treating or preventing alopecia caused by chemotherapy which comprises applying to a patient in need thereof an effective amount of a 3, 7 or 3 and 7 thia or oxa
 
       
    
                                
prostanoic acid compound represented by the formula I
 
     wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond; 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, in association with a pharmaceutical carrier adapted for topical application to mammalian skin. 
     50. The method of treating or preventing alopecia caused by chemotherapy according to claim  13  which comprises applying to a patient in need thereof an effective amount of a 3, 7 or 
                                
3 and 7 thia or oxa prostanoic acid compound represented by the formula I 3, 7 or 3 and 7 thia or oxa prostanoic acid compound represented by the formula I
 
wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, as a foam produced from a foamable liquid composition, wherein said foamable liquid composition comprises one or more of said compounds of formula I, a surfactant, 
     wherein the surfactant optionally includes a foam stabilizer and an aqueous-alcohol solvent, comprising water and an alcohol, which solvent enables said compound to be solubilized. 
     51. A foamable liquid composition, for use in the method of claim  1 , comprising one or more of the a 3, 7 or 3 and 7 thia or oxa prostanoic acid compounds represented by the formula 
                                
wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, and a surfactant, wherein the surfactant optionally includes a foam stabilizer and an aqueous-alcohol solvent, comprising water and an alcohol, which solvent enables said compound to be solubilized. 
     52. The composition of paragraph 51 wherein said aqueous-alcohol solvent further comprises an acid and a water soluble solvent, wherein said acid is an inorganic acid, or an organic acid containing eight carbons or less and said water soluble solvent is selected from the group consisting of butylene glycol, glycerin, polyglycerin, ethylene glycol, and propylene glycol and said alcohol is selected from the group consisting of methanol, ethanol, propanol and mixtures thereof.
 
53. A gel comprising a 3, 7 or 3 and 7 thia or oxa prostanoic acid compound represented by the formula I
 
                                
wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, in a pharmaceutically-acceptable solvent, comprising propylene glycol and alcohol and a crosslinked acrylic polymer thickening agent such as a Carbomer, e.g. Carbomer 934P, wherein the crosslinked acrylic polymer thickening agent is neutralized with a neutralizing agent such as diisopropanolamine. 
     54. A composition in the form of a gel comprising a 3, 7 or 3 and 7 thia or oxa prostanoic acid compound represented by the formula I 
                                
wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, a crosslinked copolymer of acrylic acid as a thickening agent, and a pharmaceutically acceptable solvent. 
     55. The composition of paragraph 54, wherein said pharmaceutically acceptable solvent is selected from the group consisting of ethanol, propanol, butanol, propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, PEG-200, PEG-400, glycerol and mixtures thereof.
 
56. A composition in the form of a gel comprising: from about 0.1 to 10% of a 3, 7 or 3 and 7 thia or oxa prostanoic acid compound represented by the formula I
 
                                
wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2 , tetrazole or triazole; 
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl or a substituted derivative thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof from about 30% to about 80% of a first solvent selected from the group consisting of propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, PEG-200, PEG-400, and glycerol; from about 10% to about 50% a second solvent selected from the group consisting of ethanol, propanol and butanol; from about 0.01% to about 50% of a crosslinked copolymer of acrylic acid; from about 0% to about 3% of a neutralizing agent and water. 
     These and other aspects of the invention will become apparent from the description of the invention which follows below. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Alopecia (baldness) a deficiency of either normal or abnormal hair, is primarily a cosmetic problem in humans. It is a deficiency of terminal hair, the broad diameter, colored hair that is readily seen. However, in the so-called bald person although there is a noticeable absence of terminal hair, the skin does contain vellus hair which is a fine colorless hair which may require microscopic examination to determine its presence. This vellus hair is a precursor to terminal hair. In accordance with the invention as described herein, compounds represented by formula I: 
                                
wherein hatched lines represent the α configuration, a triangle represents the β configuration and a dotted line represents the presence or absence of a double bond;
 
     A and B are independently selected from the group consisting of O, S and CH 2 ; 
     provided that at least one of A or B is S; 
     D represents a covalent bond or CH 2 , O, S or NH; 
     X is CO 2 R, CONR 2 , CH 2 OR, P(O)(OR) 2 , CONRSO 2 R, SONR 2  or 
     
       
                 
         
             
             
         
      
     
     Y is O, halogen or cyano; 
     Z is CH 2  or a covalent bond; 
     R is H or R 2 ; 
     R 1  is H, R 2 , phenyl, or COR 2 ; 
     R 2  is C 1 -C 5  lower alkyl or alkenyl and R 3  is hydrocarbyl, or substituted derivatives thereof, wherein the substituents maybe selected from the group consisting of C 1 -C 5  alkyl, halogen, CF 3 , CN, NO 2 , NR 2 , CO 2 R and OR in free form or a pharmaceutically acceptable salt thereof, in association with a pharmaceutical carrier adapted for topical application to mammalian skin. 
     Some examples of representative compounds useful in the practice of the present invention include the compounds shown in Table 1: 
     
       
         
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-(hydroxy)-5-(naphthyl)pent-1- 
               
               
                 enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid methyl ester. 
               
               
                   
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-(hydroxy)-5-(naphthyl)pent-1- 
               
               
                 enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid. 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-(hydroxy)-5-(naphthyl)pent-1- 
               
               
                 enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid isopropyl ester. 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzothienyl)pent-1- 
               
               
                 enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid methyl ester. 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzothienyl)pent-1- 
               
               
                 enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid. 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzothienyl)pent-1- 
               
               
                 enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid isopropyl ester. 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzofuranyl)pent-1- 
               
               
                 enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid methyl ester. 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzofuranyl)pent-1- 
               
               
                 enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid. 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxy-5-(benzofuranyl)pent-1- 
               
               
                 enyl)-5-oxocyclopentylsulfanyl]propylsulfanyl}acetic acid isopropyl ester. 
               
               
                   
               
             
          
         
       
     
     Presently preferred compounds for use in the practice of the present invention are {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxyoct-1-enyl)-5-oxocyclopentyl-sulfanyl]propylsulfanyl}acetic acid (3,7-dithia PGE1) and {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxyoct-1-enyl)-5-oxocyclopentyl-sulfanyl]propylsulfanyl}acetic acid isopropyl ester (3,7-dithia PGE1-isopropyl ester). 
     The synthesis of the compounds described above has been disclosed in U.S. Pat. Nos. 6,410,591; 6,538,018: 6,767,920 and 6,956,057 which are hereby incorporated by reference in their entireties. The invention thus relates to the use of the above compounds, or prodrugs of the active compounds, for treatment for the stimulation of hair growth. As used herein, hair growth includes hair associated with the scalp, eyebrows, eyelids (including upper and lower eyelid margins), beard, and other areas of the skin of animals including humans. 
     In accordance with one aspect of the invention, the compound is mixed with a dermatologically compatible vehicle or carrier. The vehicle which may be employed for preparing compositions of this invention may comprise, for example, aqueous solutions such as e.g., physiological salines, oil solutions or ointments. The vehicle furthermore may contain dermatologically compatible preservatives such as e.g., benzalkonium chloride, surfactants like e.g., polysorbate 80, liposomes or polymers, for example, methyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone and hyaluronic acid; these may be used for increasing the viscosity. Furthermore, it is also possible to use soluble or insoluble drug inserts when the drug is to be administered. 
     The invention is also related to dermatological compositions for topical treatment for the stimulation of hair growth which comprise an effective hair growth stimulating amount of one or more compounds as defined above and a dermatologically compatible carrier. Effective amounts of the active compounds may be determined by one of ordinary skill in the art but will vary depending on the compound employed, frequency of application and desired result, and the compound will generally range from about 0.0000001 to about 50%, by weight, of the dermatological composition, preferably from about 0.001 to about 50%, by weight, of total dermatological composition, more preferably from about 0.1 to about 30%, by weight of the composition and most preferably from 0.1, 0.2, 0.3, 0.4. 0.5, 0.6, 0.7, 0.8, 0.9 to 1.0% by weight of the composition. 
     The present invention finds application in all mammalian species, including both humans and animals. In humans, the compounds of the subject invention can be applied for example, to the scalp, face, beard, head, pubic area, upper lip, eyebrows, and eyelids. In animals raised for their pelts, e.g., mink, the compounds can be applied over the entire surface of the body to improve the overall pelt for commercial reasons. The process can also be used for cosmetic reasons in animals, e.g., applied to the skin of dogs and cats having bald patches due to mange or other diseases causing a degree of alopecia. 
     The pharmaceutical compositions contemplated by this invention include pharmaceutical compositions suited for topical and local action. 
     The term “topical” as employed herein relates to the use of a compound, as described herein, incorporated in a suitable pharmaceutical carrier, and applied at the site of thinning hair or baldness for exertion of local action. Accordingly, such topical compositions include those pharmaceutical forms in which the compound is applied externally by direct contact with the skin surface to be treated. Conventional pharmaceutical forms for this purpose include ointments, liniments, creams, shampoos, lotions, pastes, jellies, sprays, aerosols, gels, foams and the like, and may be applied in patches or impregnated dressings depending on the part of the body to be treated. The term “ointment” embraces formulations (including creams) having oleaginous, water-soluble and emulsion-type bases, e.g., petrolatum, lanolin, polyethylene glycols, as well as mixtures of these. 
     Typically, the compounds are applied repeatedly for a sustained period of time topically on the part of the body to be treated, for example, the eyelids, eyebrows, skin or scalp. The preferred dosage regimen will generally involve regular, such as daily, administration for a period of treatment of at least one month, more preferably at least three months, and most preferably at least six months. 
     For topical use on the eyelids or eyebrows, the active compounds can be formulated in aqueous solutions, creams, ointments or oils exhibiting physiologically acceptable osmolarity by addition of pharmacologically acceptable buffers and salts. Such formulations may or may not, depending on the dispenser, contain preservatives such as benzalkonium chloride, chlorhexidine, chlorobutanol, parahydroxybenzoic acids and phenylmercuric salts such as nitrate, chloride, acetate, and borate, or antioxidants, as well as additives like EDTA, sorbitol, boric acid etc. as additives. Furthermore, particularly aqueous solutions may contain viscosity increasing agents such as polysaccharides, e.g., methylcellulose, mucopolysaccharides, e.g., hyaluronic acid and chondroitin sulfate, or polyalcohol, e.g., polyvinylalcohol. Various slow releasing gels and matrices may also be employed as well as soluble and insoluble ocular inserts, for instance, based on substances forming in-situ gels. Depending on the actual formulation and compound to be used, various amounts of the drug and different dose regimens may be employed. Typically, the daily amount of compound for treatment of the eyelid may be about 0.1 ng to about 100 mg per eyelid. 
     For topical use on the skin and the scalp, the compound can be advantageously formulated using ointments, creams, liniments or patches as a carrier of the active ingredient. Also, these formulations may or may not contain preservatives, depending on the dispenser and nature of use. Such preservatives include those mentioned above, and methyl-, propyl-, or butyl-parahydroxybenzoic acid, betain, chlorhexidine, benzalkonium chloride, and the like. Various matrices for slow release delivery may also be used. Typically, the dose to be applied on the scalp is in the range of about 0.1 ng to about 100 mg per day, more preferably about 1 ng to about 10 mg per day, and most preferably about 10 ng to about 1 mg per day depending on the compound and the formulation. To achieve the daily amount of medication depending on the formulation, the compound may be administered once or several times daily with or without antioxidants. 
     In instances wherein it is desirable to maximize the contact of the active ingredients, disclosed above, with the skin of a patient, the formulation of the pharmaceutical composition of the invention may be in the form of a foam or gel. A foam is especially preferred for treating the scalp to restore lost hair or prevent hair loss, including loss of the scalp hair or eyelashes or eyebrows, resulting from chemotherapy. 
     A foamable liquid composition, for use in the method of this invention, comprises one or more of the above compounds of formula I, and one or more of: a surfactant, wherein the surfactant optionally includes a foam stabilizer; a solvent, such as water; an alcohol; an acid and a water soluble solvent. 
     In one example, the solvent includes an acid at a concentration of from 0.5 to 5 percent, by weight, of the foamable liquid composition. The acid is optionally any inorganic acid or any organic acid with chain length of eight carbons or less. A preferred composition of the solvent includes from 1 to 4 percent, by weight, lactic acid, from 1 to 50, preferably from 5 to 30 percent, by weight, of an alcohol having from one to four carbon atoms, such as methanol, ethanol, propanol and mixtures thereof, and one or more water soluble solvents, such as butylene glycol, glycerin, polyglycerin, ethylene glycol, and propylene glycol. Preferably said alcohol is ethanol and preferably said water soluble solvent is propylene glycol in an amount of from 1 to 20 percent, by weight, and more preferably from 5 to 15 percent, by weight, of the foamable liquid composition. 
     A pharmaceutically elegant gel comprising the compounds of formula I may be prepared by mixing the below-described mixtures: 
     
       
         
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 % w/w 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Part I 
               
             
          
           
               
                   
                 Purified water USP 
                 q.s. 100 
               
               
                   
                 Carbopol ® 934P 
                 0.45 
               
             
          
           
               
                 Part II 
               
             
          
           
               
                   
                 Ompound of formula 
                 0.01 to 10.0 
               
               
                   
                 propylene glycol USP 
                 10 
               
               
                   
                 alcohol USP 
                 13 
               
               
                   
                 diisopropanolamine NF 
                 0.45 
               
             
          
           
               
                 Part III 
               
             
          
           
               
                   
                 alcohol USP 
                 27 
               
               
                   
                   
               
             
          
         
       
     
     The component parts are prepared separately. Part III is then mixed with Part I. When a uniform mixture is obtained, Part II is then added using planetary mixing under vacuum until a uniform gel is obtained. 
     The invention is further illustrated by the following non-limiting examples: 
     Example 1 
     In Vivo Treatment 
     A study will be initiated to systematically evaluate the appearance of lashes and hair around the eyes of patients who are administering the drug, i.e. {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxyoct-1-enyl)-5-oxocyclopentyl-sulfanyl]propylsulfanyl}acetic acid (3,7-dithia PGE1), or {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxyoct-1-enyl)-5-oxocyclopentyl-sulfanyl]propylsulfanyl}acetic acid isopropyl ester (3,7-dithia PGE1-isopropyl ester) {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxyoct-1-enyl)-5-oxocyclopentyl-sulfanyl]propylsulfanyl}acetic acid (3,7-dithia PGE1), or {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxyoct-1-enyl)-5-oxocyclopentyl-sulfanyl]propylsulfanyl}acetic acid isopropyl ester (3,7-dithia PGE1-isopropyl ester) or combinations thereof in only one eye. Each subject is treated daily by the topical application of one drop of one of the compounds at a dosage of 1.5 .mu.g/ml/eye/day (0.03%, by weight,) to the eyelid margin by instilling the drop onto the upper eyelid margin. The non-treated eye will serve as a control. 
     Observations will be made under high magnification at the slit lamp biomicroscope. Documentation of differences between the control and treatment areas will be accomplished using a camera specially adapted for use with the slit lamp biomicroscope. 
     The results of the observations will be as follows: 
     Length of lashes: Increased length of eyelashes will be regularly observed on the side treated with drug. The difference in length varies from approximately 10% to as much as 30%. 
     Number of lashes: Increased numbers of lashes will be observed in the treated eye of each patient. In areas where there are a large number of lashes in the control eye, the increased number of lashes in the drug-treated eye will give the lashes on the treated side a more thickly matted overall appearance. 
     Auxiliary lash-like hair growth: Several patients will have an apparent increase in lash-like hair in transitional areas adjacent to areas of normal lash distribution. These prominent lash-like hairs appear to be of comparable length to the actual lashes. These long, thick lash-like hairs will be present in the central portion of the lids of several patients in a linear arrangement just above the lash line. Hairs will be present at similar locations in the control eyes but by contrast will be thinner or more fine in appearance, have less luster and pigment and are more flat against the skin of the lid typical of vellus or intermediate hairs. In several patients, lash-like terminal hairs will grow luxuriantly in the medial canthal area in the treated eye. In the corresponding control eye, vellus hairs will be seen at the same location. Lash-like hairs will be present in the lateral canthal area of the treated eye but not in the control eye in several subjects. 
     Increased growth of vellus hair on lids: Fine microscopic vellus hair will be present on the skin of the lids and will be easily seen with the slit lamp biomicroscope. This vellus hair will be typically denser adjacent to and below the lateral portion of the lower lids. While remaining microscopic, vellus hairs will increase in number, appear more robust and are much longer and thicker in treated than in control eyes in the areas below and lateral to the lower lid. 
     Perpendicular angulation of hairs: In areas where there are lash-like hairs above the lash line and in the medial and lateral canthal areas, the hairs will be much longer, thicker and heavier. 
     The above compounds are evaluated for their selectivity for various prostaglandin (PG) receptors. The results are reported in Table 2, and show that they are selective for EP 3  and EP 4  receptors. Thus, the method of the present invention may be carried out with EP 3  and EP 4  receptor agonists and/or prodrugs of EP 3  and EP 4  receptor agonists. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 EC50 (nM) on Prostanoid Receptor Functional Activity 
               
               
                 Measured by FLIPR 
               
             
          
           
               
                   
                 hDP 
                 hEP 1   
                 hEP 2   
                 hEP 3   
                 hEP 4   
                 hFP 
                 hIP 
                 hTP 
               
               
                   
                   
               
             
          
           
               
                 #1 
                 &gt;10,000 
                 304 
                 380 
                 36 
                 0.26 
                 &gt;10,000 
                 &gt;10,000 
                 561 
                 n = 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 6 
               
               
                 #2 
                 &gt;10,000 
                 2258 
                 1106 
                 44 
                 2.55 
                 &gt;10,000 
                 &gt;10,000 
                 3287 
                 n = 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 3 
               
               
                   
               
             
          
         
       
     
     Example 2 
     Topical Cream 
     A topical cream is prepared as follows: Tegacid and spermaceti are melted together at a temperature of 70-80° C. Methylparaben is dissolved in about 500 gm of water and propylene glycol, polysorbate 80, and 1 to 1 mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester are added in turn, maintaining a temperature of 75-80° C. The methylparaben mixture is added slowly to the Tegacid and spermaceti melt, with constant stirring. The addition is continued for at least 30 minutes with additional stirring until the temperature has dropped to 40-45° C. Finally, sufficient water is added to bring the final weight to 1000 gm and the preparation stirred to maintain homogeneity until cooled and congealed. 
     Example 3 
     Topical Cream 
     A topical cream is prepared as follows: Tegacid and spermaceti are melted together at a temperature of 70-80° C. Methylparaben is dissolved in water and propylene glycol, polysorbate 80, and a 1 to 1 mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester are added in turn, maintaining a temperature of 75-80° C. The methylparaben mixture is added slowly to the Tegacid and spermaceti melt, with constant stirring. The addition is continued for at least 30 minutes with additional stirring until the temperature has dropped to 40-45° C. Finally, sufficient water is added to bring the final weight to 1000 gm and the preparation stirred to maintain homogeneity until cooled and congealed. The composition will be applied to bald human scalp once daily to stimulate the growth of hair. 
     Example 4 
     Topical Ointment 
     An ointment containing 2% by weight a 1 to 1 mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester is prepared as follows: 
     White petrolatum and wool fat are melted, strained and liquid petrolatum is added thereto. The mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester, zinc oxide, and calamine are added to the remaining liquid petrolatum and the mixture milled until the powders are finely divided and uniformly dispersed. The mixture is stirred into the white petrolatum, melted and cooled with stirring until the ointment congeals. 
     The foregoing ointment can be applied topically to mammalian skin for increased rate of hair growth, and can be prepared by omitting the zinc oxide and calamine. 
     Example 5 
     Ointment 
     A dermatological ophthalmic ointment containing 10% by weight a 1 to 1 mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester is prepared by adding the active compound to light liquid petrolatum. White petrolatum is melted together with wool fat, strained, and the temperature adjusted to 45-50° C. The liquid petrolatum slurry is added and the ointment stirred until congealed. Suitably the ointment is packaged in 30 gm tubes. 
     The foregoing ointment can be applied to the eyelid to enhance the growth of eyelashes. Similarly the composition can be applied to the brow for eyebrow growth. 
     Example 6 
     Solution 
     An aqueous solution containing 5%, by weight, a 1 to 1 mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester is prepared as follows. A mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester is dissolved in water and the resulting solution is sterilized by filtration. The solution is aseptically filled into sterile containers. 
     The composition so prepared can be used in the topical treatment of baldness by application to the scalp daily. 
     Example 7 
     Lotion 
     A sample of a 1 to 1 mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester is dissolved in the vehicle of N-methylpyrrolidone and propylene glycol. The composition can be used for application to dogs or cats having hair loss due to mange or alopecia of other causes. 
     Example 8 
     Aerosol 
     An aerosol containing approximately 0.1% by weight a 1 to 1 mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester is prepared by dissolving a 1 to 1 mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester in absolute alcohol. The resulting solution filtered to remove particles and lint. This solution is chilled to about minus 30° C. To the solution is added a chilled mixture of dichlorodifluoromethane and dichlorotetrafluoroethane. Thirteen ml plastic-coated amber bottles are cold filled with 11.5 gm each of the resulting solution and capped. The composition can be sprayed on the scalp daily to stimulate the growth of hair. 
     Example 9 
     Dusting Powder 
     A powder of the compound a 1 to 1 mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester is prepared by mixing in dry form with talcum powder at a weight/weight ratio of 1:10. The powdered mixture is dusted on the fur of minks or other commercially valuable fur bearing animals and show animals for increased rate of hair growth. 
     Example 10 
     Related Compounds 
     Following the procedure of the preceding Examples, compositions are similarly prepared substituting an equimolar amount of a compound of Formula I for the 1 to 1 mixture of 3,7-dithia PGE1 and 3,7-dithia PGE1-isopropyl ester disclosed in the preceding Examples similar results are obtained. 
     Example 11 
     In-Vivo Animal Studies 
     A comparison of a topical composition comprising 0.03%, by weight, of [(1R,3R)-3-hydroxy-2-[(1E,3S)-3-hydroxyoct-1-en-1-yl]-5-oxocyclopentyl sulfanyl]propylsulfanyl}acetic acid or (3,7-dithia PGE1-isopropyl ester) with the vehicle, for the onset of hair growth and full hair growth, in a mouse model for hair growth, gave the results summarized in Table 3, below. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 First Day of New Hair Appearance and Hair grow back normal 
               
             
          
           
               
                   
                   
                   
                 First day of new 
                 First day of hair 
               
               
                   
                   
                 Animal 
                 hair appearance 
                 grow back to 
               
               
                 Group 
                 Test Article 
                 Number 
                 (Day) 
                 normal (Day) 
               
               
                   
               
             
          
           
               
                 1 
                 PDA 206 
                 101 
                 14 
                 28 
               
               
                   
                 (0.03% 3,7- 
                 102 
                 26 
                 52 
               
               
                   
                 dithia PGE2 
                 103 
                 21 
                 52 
               
               
                   
                 isopropyl ester) 
                 104 
                 18 
                 N.O. 
               
               
                   
                   
                 105 
                 16 
                 31 
               
               
                   
                   
                 106 
                 14 
                 25 
               
               
                   
                   
                 107 
                 14 
                 35 
               
               
                   
                   
                 108 
                 14 
                 26 
               
               
                   
                   
                 Mean 
                 17.13 
                 35.57 
               
               
                   
                   
                 SD 
                 4.39 
                 11.70 
               
               
                 2 
                 PDA 210 
                 201 
                 31 
                 47 
               
               
                   
                 (Vehicle) 
                 202 
                 14 
                 N.O. 
               
               
                   
                   
                 203 
                 22 
                 40 
               
               
                   
                   
                 204 
                 13 
                 21 
               
               
                   
                   
                 205 
                 14 
                 27 
               
               
                   
                   
                 206 
                 18 
                 47 
               
               
                   
                   
                 207 
                 31 
                 48 
               
               
                   
                   
                 208 
                 42 
                 55 
               
               
                   
                   
                 Mean 
                 23.13 
                 40.71 
               
               
                   
                   
                 SD 
                 10.53 
                 12.34 
               
               
                   
               
             
          
         
       
     
     The results of this comparison shows that a representative compound used in the method of treatment of this invention significantly improves the onset of hair growth and the return to normal. This result further indicates that the compounds are useful in treating alopecia caused by chemotherapy. 
     Example 12 
     Foam 
     A liquid composition for the treatment and prevention of hair loss in humans, said liquid comprising: a foamable composition, comprising. 0.03%, by weight, of a compound of formula I, e.g. [(1R,3R)-3-hydroxy-2-[(1E,3S)-3-hydroxyoct-1-en-1-yl]-5-oxocyclopentyl sulfanyl]propylsulfanyl}acetic acid or (3,7-dithia PGE1-isopropyl ester) dissolved in a solvent system, comprising an aqueous-alcoholic solvent medium; a surfactant, selected from the group consisting of: an anionic surfactant; a cationic surfactant; a non-ionic surfactant; an amphoteric surfactant and mixtures thereof and a foam stabilizer, said foam stabilizer, selected from the group consisting of: a fatty amine oxide; a quaternary amine; a derivative of cellulose; a methyl cellulose derivative; and an ethyl cellulose derivative is prepared by methods known in the art. The foamable composition has a hydrophilic-lipophilic balance (HLB) value of greater than fifteen. 
     Said composition comprises from 0.1 to 5 percent of a surfactant, preferably oleth-20, by weight, and from 0.05 to 0.5 percent of a foam stabilizer, e.g. lauryl glucoside, by weight. 
     Said solvent system comprises water; an acid, wherein said acid is selected from the group consisting of: an inorganic acid; and an organic acid comprising eight or fewer carbon atoms, e.g. lactic acid, and an alcohol comprising one to four carbon atoms. 
     Said alcohol is selected from the group consisting of methanol, ethanol, propanol and mixtures thereof. 
     Said solvent system further comprises at least one of butylene glycol, glycerin, polyglycerin, ethylene glycol and propylene glycol. 
     The foamable liquid composition includes from 30 to 80 percent water, by weight. Preferably the foamable liquid composition includes from 30 to 60 percent water, by weight. The foamable liquid composition includes an acid at a concentration of from 0.5 to 5 percent, by weight, of the foamable liquid composition, preferably from 1 to 4 percent, by weight, lactic acid; from 1 to 50, preferably from 5 to 30 percent, by weight, of an alcohol having from one to four carbon atoms, such as methanol, ethanol, propanol and mixtures thereof, and one or more water soluble solvents, such as butylene glycol, glycerin, polyglycerin, ethylene glycol, and propylene glycol. Preferably said alcohol is ethanol and preferably said water soluble solvent is propylene glycol in an amount of from 1 to 20 percent, by weight, and more preferably from 5 to 15 percent, by weight, of the foamable liquid composition. 
     Said foam is utilized by a method of delivering said composition as a foam for the treatment and prevention of hair loss in humans, said method comprising the steps of: providing said foamable composition in a container, producing a foam from said foamable liquid composition and dispensing a measured dosage of said foam from said container onto a patient. 
     Said step of producing a foam may comprise a step of: mixing said foamable composition and air contained within said container. 
     Said foam is administered to the scalp or other body part of a patient and is maintained thereon for a time sufficient to obtain the desired therapeutic effect. 
     Example 13 
     Gel 
     A pharmaceutically elegant gel comprising 0.03%, by weight, of a compound of formula I, e.g. [(1R,3R)-3-hydroxy-2-[(1E,3S)-3-hydroxyoct-1-en-1-yl]-5-oxocyclopentyl sulfanyl]propylsulfanyl}acetic acid or (3,7-dithia PGE1-isopropyl ester and alcohol and a crosslinked acrylic polymer thickening agent such as a Carbomer, e.g. Carbomer 934P, is prepared as described below. 
     The crosslinked acrylic polymer thickening agent is neutralized with a neutralizing agent such as diisopropanolamine. 
     The gel comprises from 0.001% to 10% (3,7-dithia PGE1-isopropyl ester) by weight. More preferably said gel comprises from 0.01% to 0.5% (3,7-dithia PGE1-isopropyl ester), by weight, most preferably said composition comprises 0.3%, by weight 
     Said pharmaceutically acceptable solvent is selected from the group consisting of ethanol, propanol, butanol, propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, PEG-200, PEG-400, glycerol and mixtures thereof. 
     Most preferably, said solvent is selected from the group consisting of ethanol and isopropanol. 
     Alternatively, said solvent selected from the group consisting of propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, PEG-200, PEG-400, and glycerol. 
     Most preferably, said solvent is propylene glycol. 
     In a second alternative embodiment of the invention, said solvent comprises a mixture comprising a first solvent selected from the group consisting of ethanol, propanol and butanol and a second solvent selected from the group consisting of propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, PEG-200, PEG-400, and glycerol. 
     Preferably, in said second alternative embodiment of the invention, said solvent comprises a mixture of ethanol and propylene glycol. 
     The gel further comprising a neutralizing agent, wherein said neutralizing agent may be selected from the group consisting of ammonium hydroxide, arginine, 2-amino-2-methyl-1-propanol, dimethanolamine, dibutanolamine, diisobutanolamine, tributanolamine, triisobutanolamine, tri-sec-butanolamine, tripropylamine, ethanolamine, diethanolamine, triethanolamine, PEG-15 cocamine, diisopropanolamine, methylethanolamine, diisopropylamine, dipropylenetriamine, tromethamine, isopropylamine ethylene diamine, triisopropanolamine, tetrahydroxypropyl ethylenediamine, trimethamine, 2-aminobutanol, aminoethyl propanediol, aminomethyl propanediol, aminomethylpropanol, sodium hydroxide, and potassium hydroxide. 
     The component parts are prepared separately. Part III is then mixed with Part I. When a uniform mixture is obtained, Part II is then added using planetary mixing under vacuum until a uniform gel is obtained. 
     
       
         
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 % w/w 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Part I 
               
             
          
           
               
                   
                 Purified water USP 
                 q.s. 100 
               
               
                   
                 Carbopol ® 934P 
                 0.45 
               
             
          
           
               
                 Part II 
               
             
          
           
               
                   
                 (3,7-dithia PGE1-isopropyl ester) 
                 0.3 
               
               
                   
                 propylene glycol USP 
                 10 
               
               
                   
                 alcohol USP 
                 13 
               
               
                   
                 diisopropanolamine NF 
                 0.45 
               
             
          
           
               
                 Part III 
               
             
          
           
               
                   
                 alcohol USP 
                 27 
               
               
                   
                   
               
             
          
         
       
     
     The component parts are prepared separately. Part III is then mixed with Part I. When a uniform mixture is obtained, Part II is then added using planetary mixing under vacuum until a uniform gel is obtained. 
     While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. For example, while the above examples demonstrates the use of {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxyoct-1-enyl)-5-oxocyclopentyl-sulfanyl]propylsulfanyl}acetic acid (3,7-dithia PGE1), {3-[(1R,2S,3R)-3-Hydroxy-2-((S)-(E)-3-hydroxyoct-1-enyl)-5-oxocyclopentyl-sulfanyl]propylsulfanyl}acetic acid isopropyl ester (3,7-dithia PGE1-isopropyl ester) and a 50/50 mixture thereof in the method of the present invention, these compounds demonstrate that the combination of an EP 4  agonist prodrug with an EP 3  agonist is effective in a method for stimulating hair growth in a mammalian species comprising the application to mammalian skin of an effective amount of said combination.