Cosmetic composition comprising an ester of pyroglutamic acid
This is a continuation application of Ser. No. 07/521,809 filed May 10, 1990, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to cosmetic and pharmaceutical compositions for topical application to mammalian skin or hair, containing an ester of pyroglutamic acid which is capable of promoting hair growth, especially terminal hair growth on the human scalp. 
     BACKGROUND 
     The Hair Growth Cycle 
     It should be explained that in most mammals, hair does not grow continuously, but undergoes a cycle of activity involving alternate periods of growth and rest. The hair growth cycle can be divided into three main stages, namely: 
     (i) the growth phase known as anagen, during which the hair follicle penetrates deep into the dermis with the cells of the bulb dividing rapidly and differentiating to form the hair, 
     (ii) the transitional stage known as catagen, which is heralded by the cessation of mitosis, and during which the follicle regresses upwards through the dermis and hair growth ceases, 
     (iii) the resting stage known as telogen, in which the regressed follicle contains a small secondary germ with an underlying ball of tightly packed dermal papilla cells. 
     The initiation of a new anagen phase is revealed by rapid proliferation in the germ, expansion of the dermal papilla and elaboration of basement membrane components. The hair cycle is then repeated many times until, as a consequence of the onset of male pattern baldness, most of the hair follicles spend an increasing proportion of their time in the telogen stage, and the hairs produced become finer, shorter, and less visible; this is known as terminal to vellus transformation. 
     PRIOR ART 
     Alleged Baldness Cures 
     Although there have been many claims in the scientific literature to the promotion or maintenance of hair growth by the topical application of hair tonics and the like, with the possible exception of minoxidil, none has been shown to be sufficiently free from disadvantageous clinical side effects, whether administered topically, orally or systemically, to warrant commercial exploitation as an ethical pharmaceutical, proprietary medicine, or as a cosmetic product. Possibly, the only means which has met with partial success for growing hair on the bald or balding human head is by transplantation of hair to the bald areas. This is, however, an extremely painful operation and is not always successful. Furthermore, it is immediately apparent to the casual observer that the subject has received a hair transplant and it may take many months or even years before hair regrowth, following this operation, assumes an appearance which resembles that of the original naturally growing hair. 
     Among the many hair regrowth studies that have been reported in the literature, there is included the work of Bazzano as described in PCT International Publication No. WO 85/04577. This publication describes a composition which is useful for increasing the rates of hair growth on mammalian skin, prolonging the anagen phase of the hair growth cycle and for treating various types of alopecias. The composition in question comprises a pyrimidine carbamate. 
     It has also been reported in U.S. Pat. No. 4,139,619 to Chidsey assigned to the Upjohn Company, that a topical composition comprising minoxidil as the free base or acid addition salt thereof, or certain specified related iminopyrimidines, is useful in stimulating the conversion of vellus hair to growth as terminal hair, as well as increasing the rate of growth of terminal hair. 
     In spite of the apparent stimulation of hair growth or regrowth reported independently by Bazzano and Chidsey, following topical application of minoxidil or related compounds, there is general concern that systemic side-effects can result, particularly following topical application of minoxidil. Thus it is generally recognised in the medical literature that the side effects of orally administered minoxidil are very serious, and include fluid retention, tachycardia, dyspnea, gynecomastia, fatigue, nausea and cardiotoxicity. There is also evidence that certain side effects have been experienced following topical application of minoxidil. 
     BACKGROUND TO THE INVENTION 
     During studies into the effects of esters of pyroglutamic acid on human skin, certain unexpected responses were observed which suggested that these substances may be capable of promoting hair growth. This was tested and evidence obtained to substantiate this hypothesis. 
     DEFINITION OF THE INVENTION 
     Accordingly, the invention provides a preserved composition suitable for topical application to mammalian skin or hair for inducing, maintaining or increasing hair growth, which comprises: 
     (i) an effective amount of from 0.0001 to 99% by weight of an ester of pyroglutamic acid having the structure (1): ##STR1##  where aryl group, or a C 1  to C 30  alkyl, branched alkyl or alkenyl group; and 
     (ii) from 1 to 99.999% by weight of a cosmetically acceptable vehicle for the ester; 
     the total amount of the ester of pyroglutamic acid present in the composition being sufficient to increase hair growth in the rat, when said composition is applied topically thereto over a period of no more than 3 months, by at least 10% more than that obtainable using a control composition from which the said ester has been omitted, in accordance with the Rat Hair Growth Test. 
    
    
     DISCLOSURE OF THE INVENTION 
     The Ester of Pyroglutamic Acid 
     According to the invention, the composition comprises an ester of pyroglutamic acid, having the structure: ##STR2## where R is an aryl group, or a C 1  to C 30  alkyl, branched alkyl or alkenyl group. 
     The composition according to the invention can also comprise mixtures of said esters. 
     The preferred esters of pyroglutamic acid are those where R in structure (1) is a C 1  to C 20  alkyl group, particularly preferred examples of which are: 
     
         ______________________________________                                    
                   Promotor No.                                           
                   in Examples                                            
______________________________________                                    
pyroglutamic acid n-propyl ester                                          
                     1                                                    
pyroglutamic acid n-butyl ester                                           
                     2                                                    
pyroglutamic acid n-pentyl ester                                          
                     3                                                    
pyroglutamic acid n-hexyl ester                                           
                     4                                                    
pyroglutamic acid n-heptyl ester                                          
                     5                                                    
pyroglutamic acid n-octyl ester                                           
                     6                                                    
pyroglutamic acid n-nonyl ester                                           
                     7                                                    
pyroglutamic acid n-decyl ester                                           
                     8                                                    
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     The total amount of ester of pyroglutamic acid present in the composition according to the invention is sufficient to increase hair growth in the rat, the model selected for this test, when said composition is applied topically thereto over a period of no more than 3 months, by at least 10% more than that obtainable using a control composition from which the said ester have been omitted, in accordance with the Rat Hair Growth Test. 
     Preferably, the amount of ester should be sufficient to increase hair growth in the rat by at least 20%, more preferably by at least 30%, most preferably by at least 40% and ideally by at least 50%. 
     The effective amount which is sufficient to induce, maintain or increase hair growth will depend on the effectiveness of the ester, some being more effective than others, but in general, an amount of from 0.0001 to 99%, preferably from 0.01 to 20% by weight of the composition will provide an adequate dose to the skin after topical application. 
     Preservation of the Composition 
     The composition according to the invention is preferably preserved in such a manner that it will enjoy an extended shelf life following manufacture and prior to sale and use. Ideally the composition will have an indefinite shelf life. 
     It is accordingly apparent that the ester is likely to be prone to attack by bacteria, moulds and fungi and other microbial influences, particularly at pH values near that of the skin that characterise the preferred composition. The shelf-life of the composition can therefore be unacceptably short due to the biodegradation of the ester unless steps are taken to preserve the composition. 
     In order to be preserved, the composition should preferably be free, or substantially free, from viable microbial contaminants that are capable of resulting in microbial spoilage of the composition, and/or biodegradation of the ester prior to topical application of the composition to mammalian skin or hair. It is to be understood, however, that the invention is also concerned with compositions, as herein defined, which may contain viable but dormant microorganisms, such as bacterial spores, provided that the conditions of preservation do not result in substantial proliferation of the microorganisms prior to use of the composition. 
     Examples of methods that can be employed to achieve preservation of the composition, includes the following: 
     (i) Sterilisation 
     The composition according to the invention can be preserved by sterilisation to remove or kill substantially all viable microbial contaminants. This can be achieved for example by irradiation using a lethal dose of gamma rays, by heat sterilisation or by ultrafiltration using techniques that are well established in the pharmaceutical industry. 
     (ii) Chemical Preservative 
     The composition according to the invention can also be preserved by including in it a chemical preservative which functions to prevent the growth of or kill bacteria, fungi or other microorganisms. 
     Examples of chemical preservatives include ethanol, benzoic acid, sodium benzoate, sorbic acid, potassium sorbate, sodium propionate and the methyl, ethyl, propyl and butyl esters of p-hydroxybenzoic acid. The amount of chemical preservative that can be incorporated in the composition according to the invention will generally be from 0.05 to 5%, preferably from 0.1 to 2% by weight, the amount chosen being sufficient to arrest microbial proliferation. 
     (iii) Water activity depressants 
     The composition according to the invention can also be preserved by the inclusion of a water activity depressant such as glycerol, propylene glycol, sorbitol, sugars and salts, for examples alkali metal halides, sulphates and carboxylates. When employing a water activity depressant, sufficient should be incorporated in the composition according to the invention to reduce the water activity (α w ) from 1 to &lt;0.9, preferably to &lt;0.85 and most preferably &lt;0.8, the lowest of these values being that at which yeasts, moulds and fungi will not proliferate. 
     pH 
     The esters of pyroglutamic acid may be susceptable to hydrolysis, particularly when the pH value of the composition is alkaline. It is accordingly preferred that the composition, when aqueous, should have an acid pH value. The preferred pH value of the composition, when aqueous, is from 2 to &lt;7, ideally from 4 to 6.5. 
     The Vehicle 
     The composition according to the invention also comprises a solid, semi-solid or liquid cosmetically and/or physiologically acceptable vehicle, to enable the ester to be conveyed to the skin at an appropriate dilution. The nature of the vehicle will depend upon the method chosen for topical administration of the composition. The vehicle can itself be inert or it can possess physiological or pharmaceutical benefits of its own. 
     The selection of a vehicle for this purpose presents a wide range of possibilities depending on the required product form of the composition. Suitable vehicles can be classified as described hereinafter. 
     It should be explained that vehicles are substances which can act as diluents, dispersants, or solvents for the ester which therefore ensure that they can be applied to and distributed evenly over the hair and/or scalp at an appropriate concentration. The vehicle is preferably one which can aid penetration of the esters into the skin to reach the immediate environment of the hair follicle. Compositions according to this invention can include water as a vehicle, and/or at least one cosmetically acceptable vehicle other than water. 
     Vehicles other than water that can be used in compositions according to the invention can include solids or liquids such as emollients, solvents, humectants, thickeners and powders. Examples of each of these types of vehicles, which can be used singly or as mixtures of one or more vehicles, are as follows: 
     Emollients, such as stearyl alcohol, glyceryl monoricinoleate, glyceryl monostearate, propane-1,2-diol, butane-1,3-diol, mink oil, cetyl alcohol, ispropyl isostearate, stearic acid, isobutyl palmitate, isocetyl stearate, oleyl alcohol, isopropyl laurate, hexyl laurate, decyl oleate, octadecan-2-ol, isocetyl alcohol, cetyl palmitate, dimethylpolysiloxane, di-n-butyl sebacate, isopropyl myristate, isopropyl palmitate, isopropyl stearate, butyl stearate, polythylene glycol, triethylene glycol, lanolin, sesame oil, coconut oil, arachis oil, castor oil, acetylated lanolin alcohols, petroleum, mineral oil, butyl myristate, isostearic acid, palmitic acid, isopropyl linoleate, lauryl lactate, myristyl lactate, decyl oleate, myristyl myristate; 
     Propellants, such as trichlorofluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane, monochlorodifluoromethane, trichlorotrifluoroethane, propane, butane, isobutane, dimethyl ether, carbon dioxide, nitrous oxide; 
     Solvents, such as ethyl alcohol, methylene chloride, isopropanol, castor oil, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, dimethyl sulphoxide, dimethyl formamide, tetrahydrofuran; 
     Humectants, such as glycerin, sorbitol, sodium 2-pyrrolidone-5-carboxylate, soluble collagen, dibutyl phthalate, gelatin; 
     Powders, such as chalk, talc, fullers earth, kaolin, starch, gums, colloidal silicon dioxide, sodium polyacrylate, tetra alkyl and/or trialkyl aryl ammonium smectites, chemically modified magnesium aluminium silicate, organically modified montmorillonite clay, hydrated aluminium silicate, fumed silica, carboxyvinyl polymer, sodium carboxymethyl cellulose, ethylene glycol monostearate. 
     The amount of vehicle in the composition, including water if present, should preferably be sufficient to carry at least a portion of a selected ester to the skin in an amount which is sufficient effectively to enhance hair growth. The amount of the vehicle can comprise the balance of the composition, particularly where little or no other ingredients are present in the composition. Accordingly, the vehicle or vehicles can comprise from 1 to 99.99%, preferably from 50 to 99.5% and ideally from 90 to 99% by weight of the composition. 
     Perfume 
     The composition according to the invention can also optionally comprise a perfume in an amount sufficient to make the composition acceptable to the consumer and pleasant to use. Usually, the perfume will form from 0.01 to 10% by weight of the composition. 
     Activity Enhancer 
     The composition according to the invention can also optionally comprise an activity enhancer. 
     The activity enhancer can be chosen from a wide variety of molecules which can function in different ways to enhance the hair growth effects of the ester. Particular classes of activity enhancers include other hair growth stimulants, penetration enhancers and cationic polymers, whose presence can further improve the delivery of the ester through the stratum corneum to its site of action in the immediate environment of the hair follicle. 
     Some activity enhancers can also function as vehicles for the ester. 
     (a) Other Hair Growth Stimulants 
     Examples of other substances which themselves possess the ability to stimulate or increase hair growth include, for example; 
     Benzalkonium chloride 
     Benzethonium chloride 
     Phenol 
     Estradiol 
     Diphenhydramine hydrochloride 
     Chlorpheniramine maleate 
     Chlorophyllin derivatives 
     Cholesterol 
     Salicylic acid 
     Cystine 
     Red pepper tincture 
     Benzyl nicotinate 
     dl-Menthol 
     Peppermint oil 
     Calcium pantothenate 
     Panthenol 
     Castor oil 
     Hinokitiol 
     Prednisolone 
     Resorcinol 
     Further substances which themselves possess the ability to increase the rate of terminal hair growth include: 
     α-1,4 esterified disaccharides described by Choay S.A. in EP-A-O 064,012, having the structure (2): ##STR3## where Z represents a functional nitrogen group, such as an azide or a group having the structure --NHB, in which B represents --H or a functional group such as acetyl or sulphate as a salt with an organic or mineral cation; 
     M represents --H or SO 3  M 1 , where M 1  is an organic or metallic cation, particularly an alkali metal; or an acetyl group; 
     R represents a C 1  to C 4  alkyl radical, especially methyl; or an aryl radical; 
     A represents a functional group such as an acid or --COOR 1 , where R 1  represents --H or a C 1  to C 4  alkyl radical, especially methyl; or a metal, especially an alkali metal; 
     esterified oligosaccharides as described by Unilever in EP-A-0 211 610, including at least one esterified disaccharide unit consisting of a uronic acid residue having the structure (3): ##STR4## and a hexosamine residue having the structure (4): ##STR5## where R&#39; is --H, C 3  to C 10  alkyl or ##STR6## R&#34; is --H, C 1  to C 4  alkyl, --CO(CH 2 ) m  CH 3 , --SO 3  M, 
     R&#39;&#34; is --H, --CO(CH 2 ) m  CH 3 , or --SO 3  M, 
     M is --H, or a metallic or organic cation 
     n is 0 or an integer of from 1 to 7, and 
     m is 0 or the integer 1 or 2; 
     the groups designated R&#34; being the same or different, one R&#34; group from each pyranose ring structure being linked by a glycosidic linkage having the configuration α-1,3, α-1,4, β-1,3 or β-1,4; and the --COOR&#39;, --CH 2  OR&#34; and --OR&#34; groups being of either configuration with respect to the pyranose rings; 
     Minoxidil glucuronides, as described by Unilever in EP-0 242 967, 
     Minoxidil sulphates, as described by The Upjohn Co. in WO 86/04231, and 
     Minoxidil, and other derivatives thereof as described by The Upjohn Co, in U.S. Pat. No. 4,139,619. 
     Particularly preferred mixtures of minoxidil and an ester according to the invention include the following: 
     Minoxidil and pyroglutamic acid n-pentyl ester 
     Minoxidil and pyroglutamic acid n-hexyl ester 
     Minoxidil and pyroglutamic acid n-heptyl ester 
     Minoxidil and pyroglutamic acid n-octyl ester 
     (b) Penetration Enhancers 
     As has been stated earlier, the presence of a penetration enhancer can potentiate the benefit of the ester, by improving its delivery through the stratum corneum to its site of action in the immediate environment of the hair follicle close to the dermal papilla. 
     The penetration enhancer can accordingly function in a variety of ways. It can for example, improve the distribution of the ester on the skin surface or, it can increase its partition into the skin from the composition when applied topically, so aiding its passage to its site of action. Other mechanisms enhancing the benefit of the ester may also be involved. 
     Examples of penetration enhancers include: 
     2-methyl propan-2-ol 
     Propan-2-ol 
     Ethyl-2-hydroxypropanoate 
     Hexan-2,5-diol 
     POE(2) ethyl ether 
     Di(2-hydroxypropyl) ether 
     Pentan-2,4-diol 
     Acetone 
     POE(2) methyl ether 
     2-hydroxypropionic acid 
     2-hydroxyoctanoic acid 
     Propan-1-ol 
     1,4 Dioxane 
     Tetrahydrofuran 
     Butan-1,4-diol 
     Propylene glycol dipelargonate 
     Polyoxypropylene 15 stearyl ether 
     Octyl alcohol 
     POE ester of oleyl alcohol 
     Oleyl alcohol 
     Lauryl alcohol 
     Dioctyl adipate 
     Dicapryl adipate 
     Diisopropyl adipate 
     Diisopropyl sebacate 
     Dibutyl sebacate 
     Diethyl sebacate 
     Dimethyl sebacate 
     Dioctyl sebacate 
     Dibutyl suberate 
     Dioctyl azelate 
     Debenzyl sebacate 
     Dibutyl phthalate 
     Dibutyl azelate 
     Ethyl myristate 
     Dimethyl azelate 
     Butyl myristate 
     Dibutyl succinate 
     Didecyl phthalate 
     Decyl oleate 
     Ethyl caproate 
     Ethyl salicylate 
     Isopropyl palmitate 
     Ethyl laurate 
     2-ethyl-hexyl pelargonate 
     Isopropyl isostearate 
     Butyl laurate 
     Benzyl benzoate 
     Butyl benzoate 
     Hexyl laurate 
     Ethyl caprate 
     Ethyl caprylate 
     Butyl stearate 
     Benzyl salicylate 
     2-hydroxypropanoic acid 
     2-hyroxyoctanoic acid, 
     Further examples of penetration enhancers include:- 
     Dimethyl sulphoxide 
     N,N-Dimethyl acetamide 
     N,N-Dimethyl formamide 
     2-Pyrrolidone 
     1-Methyl-2-pyrrolidone 
     5-Methyl-2-pyrrolidone 
     1,5-Dimethyl-2-pyrrolidone 
     1-Ethyl-2-pyrrolidone 
     Phosphine oxides 
     Sugar esters 
     Tetrahydrofurfural alcohol 
     Urea 
     Diethyl-m-toluamide, and 
     1-Dodecylazacyloheptan-2-one 
     Further examples of penetration enhancers include surface active agents, preferred examples of which include: 
     (i) 
     Anionic surface active agents, such as metallic or alkanolamine salts of fatty acids for example sodium laurate and triethanolamine oleate; 
     alkyl benzene sulphonates, for example triethanolamine dodecyl benzene sulphonate; 
     alkyl sulphates, for example sodium lauryl sulphate; 
     alkyl ether sulphates, for example sodium lauryl ether sulphate [2 to 8 EO]; 
     sulphosuccinates, for example sodium dioctyl sulphosuccinate; 
     monoglyceride sulphates, for example sodium glyceryl monostearate monosulphate; 
     isethionates, for example sodium isethionate; 
     methyl taurides, for example Igepon T; 
     acylsarcosinates, for example sodium myristyl sarcosinate; 
     acyl peptides, for example Maypons and Lamepons; 
     acyl lactylates, 
     polyalkoxylated ether glycollates, for example trideceth-7 carboxylic acid; 
     phosphates, for example sodium dilauryl phosphate. 
     (ii) 
     Cationic surface active agents, such as amine salts, for example sapamin hydrochloride; 
     quartenary ammonium salts, for example Quaternium 5, Quaternium 31 and Quaternium 18; 
     (iii) 
     Amphoteric surface active agents, such as imidazol compounds, for example Miranol; 
     N-alkyl amino acids, such as sodium cocaminopropionate and asparagine derivatives; 
     betaines, for example cocoamidopropylbetaine 
     (iv) 
     Nonionic surface active agents, such as fatty acid alkanolamides, for example oleic ethanolamide; 
     esters of polyalcohols, for example Span; 
     polyglycerol esters, for example that esterified with C 12-18  fatty acids and one or several OH groups; 
     polyalkoxylated derivatives, for example polyoxy:polyoxyethylene stearate, and octylphenoxy polyethoxyethanol (TRITON X-100); 
     ethers, for example polyoxyethylene lauryl ether; 
     ester ethers, for example Tween; 
     amine oxides, for example coconut and dodecyl dimethyl amine oxides. 
     Mixtures of two or more of the above surface active agents can be employed in the composition according to the invention. 
     (c) cationic polymers chosen from: 
     Guar Hydroxypropyltrimonium chloride 
     Quaternium-19 
     Quaternium-23 
     Quaternium-40 
     Quaternium-57 
     Poly(dipropyldiallylammonium chloride) 
     Poly(methyl-β-propaniodiallylammonium chloride) 
     Poly(diallylpiperidinium chloride) 
     Poly(vinyl pyridinium chloride) 
     Quaternised poly (vinyl alcohol) 
     Quaternised poly (dimethylaminoethylmethacrylate); 
     and mixtures thereof 
     The amount of activity enhancer, when employed in accordance with the invention, will normally be from 0.1 to 50%, preferably from 0.5 to 25% and most preferably from 0.5 to 10% by weight of the composition. 
     Other Hair Growth Promoter Adjuncts 
     The composition according to the invention can also contain adjuncts other than those already mentioned, depending on the form of the intended product. It is, for example, possible to include antiseptics, preservatives, antioxidants, emulsifiers and colouring agents, which can improve the stability and consumer appeal of the composition. 
     The composition according to the invention can also be employed as a vehicle for a wide variety of cosmetically or pharmaceutically active ingredients, particularly ingredients which have some beneficial effect other than the promotion of hair growth when applied to the skin. 
     Process 
     The invention also provides a process for the preparation of a composition suitable for topical application to mammalian skin or hair which comprises mixing a ester of pyroglutamic acid, as herein defined, with a suitable vehicle to provide a composition according to the invention, in which the ester forms from 0.0001 to 99% by weight of the composition. 
     Product Form and Container 
     The compositions of the invention can be formulated as liquids, for example as a lotion, shampoo, milk or cream for use in conjunction with an applicator such as a roll-ball applicator, or a spray device such as an aerosol can containing propellant, or a container fitted with a pump to dispense the liquid product. Alternatively, the compositions of the invention can be solid or semi-solid, for example sticks, creams or gels, for use in conjunction with a suitable applicator or simply a tube, bottle or lidded jar, or as a liquid-impregnated fabric, such as a tissue wipe. 
     The invention accordingly also provides a closed container containing a composition as herein defined. 
     Use of the Ester of Pyroglutamic Acid for Inducing, Maintaining or Increasing Hair Growth 
     The invention also provides for the use of an ester of pyroglutamic acid, as herein defined, for topical application to mammalian skin or hair for inducing, maintaining or increasing hair growth. 
     The compositions according to the invention are primarily intended for topical application to the scalp of the human subject, particularly where the head is already bald or balding, in order to promote the regrowth of terminal hair. The compositions can also be applied profilactically to the hair and hence the scalp to reduce or prevent the onset of baldness. 
     The amount of the composition and the frequency of application to the hair and/or scalp can vary widely, depending on personal needs, but it is suggested as an example that topical application of from 0.1 to 5g daily containing from 0.00001 to 1 g of a selected chemical inhibitor over the period of at least six months will in most cases result in an improvement in hair growth. 
     EVALUATION OF EFFICACY OF ESTERS OF PYROGLUTAMIC ACID AS HAIR GROWTH PROMOTERS USING THE RAT MODEL 
     The Rat Hair Growth Test 
     The effect of compounds on hair growth was assessed using male albino Wistar rats as an animal model. The rats were chosen from as few litters as possible and were each approximately 42 days of age at the start of the test. Each rat was housed individually to prevent licking. 
     In each comparison, 10 rats were used in each group and hair growth was assessed as follows: 
     A small patch of normal skin (4 cm×4 cm) on the upper back of each rat was clipped at the start and 0.3 ml of a hair growth stimulant composition (or a control) applied topically twice daily and once on Saturdays and Sundays to each clipped area. The concentration of test compound in the composition was chosen from 0.01 to 20% by weight. 
     It is to be understood that the potency of each of the esters of pyroglutamic acid in terms of its ability to induce, maintain or increase hair growth is unlikely to be uniform, some being more potent than others, and therefore the concentration of any ester chosen for thorough evaluation must be carefully selected after preliminary testing to determine its potential as a hair growth promoter. In any case, this concentration will lie within the range of from 0.01 to 20% by weight as stipulated above. 
     Hair was clipped from the area of the patch twice weekly, collected and weighed at each time point over a standard period of 3 months, and cumulative hair weight calculated. From these data, it was possible to estimate the effect of an ester of pyroglutamic acid as a hair growth stimulant (test compound) on the amount and duration of hair growth during the experiment. A positive response, i.e. an increase of at least 10% by weight of hair after 3 months treatment, compared with a control indicates the potential of the test compound to prevent hair loss and/or reverse baldness in human subjects. 
     Accordingly, when the esters, as herein defined, are assessed either individually or in combination as test compound by the Rat Hair Growth Test, an increase of at least 10% by weight of hair after 3 months treatement will be obtained. Usually, the 10% by weight minimum value will be attained well before the end of this 3 months period. 
     EXPERIMENT 1 
     Measurement of Hair Growth Following Topical Application of 1% w/v Pyroglutamic Acid n-Hexyl Ester 
     Topical treatment with a composition according to the invention was found to stimulate hair growth. In this example, the effect of topical application of pyroglutamic acid n-hexyl ester is shown. The test solution in this experiment contained 1% (w/v) of the ester in the form of a solution in 50% w/v aqueous ethanol. The hair growth results are shown below in Table 1. 
     
                       TABLE 1                                                     
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               Mean Cumulative                                            
               Hair Weight   Significance                                 
               (mg) ± sd, Level                                        
Treatment      after 58 days (vs control)                                 
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1% (w/v) pyroglutamic                                                     
               711.1 ± 96.1                                            
                             p &lt; 0.05*                                    
acid n-hexyl ester                                                        
Control (50% w/v                                                          
               595.5 ± 126.3                                           
aqueous ethanol)                                                          
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 *statistically significant                                               
 
    
     These results indicate that a statistically significant increase (19%) in hair growth was obtained in this experiment. 
     Measurement of Hair Growth Following Topical Application of 5% W/V Pyroglutamic Acid n-Hexyl or n-Octyl Esters 
     Experiment 1 was repeated using seperately 5% w/v pyroglutamic acid n-hexyl and n-octyl esters in place of the 1% w/v pyroglutamic acid used in that Experiment. The hair growth results are shown below in Table 2. 
     
                       TABLE 2                                                     
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               Mean Cumulative                                            
               Hair Weight   Significance                                 
               (mg) + sd,    Level                                        
Treatment      after 49 days (vs. Control)                                
______________________________________                                    
5% (w/v)       454.7 ± 74.1                                            
                             p = 0.025*                                   
pyroglutamic                                                              
acid n-hexyl ester                                                        
5% (w/v)       549.0 ± 124.4                                           
                             p = 0.002*                                   
pyroglutamic                                                              
acid n-octyl ester                                                        
Control (50% w/v                                                          
               377.5 ± 66.6                                            
aqueous ethanol)                                                          
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 *statistically significant                                               
 
    
     These results indicate a 20% and a 45% increase in hair weight (i.e. growth) respectively. 
     EXAMPLES 
     The invention is illustrated by the following examples, in each of which the selected pyroglutamic acid ester is identified as the hair growth promoter enumerated hereinbefore. 
     EXAMPLE 1 
     This Example illustrates a lotion according to the invention which is suitable for topical application to the scalp in order to promote hair growth. The lotion has the following formulation: 
     
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              % w/w                                                       
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Promoter No. 1  0.1                                                       
ethanol          99.995                                                   
perfume         q.s.                                                      
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     EXAMPLE 2 
     This Example illustrates a hair tonic which is suitable for application to hair or scalp. 
     The hair tonic has the following formulation: 
     
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              % w/w                                                       
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Promoter No. 2  0.8                                                       
ethanol         50                                                        
water           49                                                        
perfume         q.s.                                                      
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     EXAMPLE 3 
     This Example also illustrates a lotion which is suitable for topical application to the scalp. The lotion has the following formulation: 
     
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              % w/w                                                       
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Promoter No. 3  1.5                                                       
propan-2-ol     10                                                        
ethanol         88.5                                                      
perfume         q.s.                                                      
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     EXAMPLE 4 
     This Example also illustrates a hair tonic which is suitable for application to hair or scalp. 
     The hair tonic has the following formulation: 
     
         ______________________________________                                    
              % w/w                                                       
______________________________________                                    
Promoter No. 4  0.2                                                       
ethanol         40                                                        
water           59.80                                                     
perfume         q.s.                                                      
______________________________________                                    
 
    
     EXAMPLES 5 to 8 
     The following formulations represent lotions which can be used topically in the treatment of bald or balding male or female heads. 
     
         ______________________________________                                    
            % w/w                                                         
            5     6         7       8                                     
______________________________________                                    
Hydroxyethyl cellulose                                                    
              0.4     --        0.4   --                                  
Absolute ethanol                                                          
              25      25        25     25                                 
Propane-1,2-diol                                                          
              --      --        38.4                                      
              38.4                                                        
Butane-1,3-diol                                                           
              38.4    38.8      --    --                                  
Paramethyl benzoate                                                       
              0.2     0.2       0.2                                       
                    0.2                                                   
Promoter No. 5                                                            
              5       --        --    --                                  
Promoter No. 6                                                            
              --      1         --    --                                  
Promoter No. 7                                                            
              --      --        0.8   --                                  
Promoter No. 8                                                            
              --      --        --                                        
                   0.6                                                    
Perfume       1       1         1      1                                  
Water to      100     100       100   100                                 
______________________________________                                    
 
    
     EXAMPLES 9 to 12 
     The following formulations represent creams which can be used in the treatment of baldness. 
     
         ______________________________________                                    
           % w/w                                                          
           9     10        11      12                                     
______________________________________                                    
Cetyl alcohol                                                             
             4       4         4     4                                    
polyoxyethylene (10)                                                      
Cetyl alcohol                                                             
             4       4         4     4                                    
Mineral oil  4       2         --    --                                   
Paraffin wax --      2         4     --                                   
Partial glyceride                                                         
             --      --        --    4                                    
of palmitic and                                                           
stearic acids                                                             
Promoter No. 1                                                            
             2       --        --    --                                   
Promoter No. 2                                                            
             --      1.5       --    --                                   
Promoter No. 3                                                            
             --      --        2     --                                   
Promoter No. 4                                                            
             --      --        --    1                                    
Triethanolamine                                                           
             0.75    0.75      0.75                                       
             0.75                                                         
Butane-1,3-diol                                                           
             3       3         3     3                                    
Xanthan gum  0.3     0.3       0.3                                        
                               0.3                                        
Preservative 0.4     0.4       0.4                                        
                               0.4                                        
Perfume      q.s.    q.s.      q.s.                                       
                  q.s.                                                    
Water to     100     100       100   100                                  
______________________________________                                    
 
    
     EXAMPLE 13 
     This Example illustrates a water-in-oil high internal phase emulsion containing an ester according to the invention. 
     The emulsion consisted of 10% by volume oily phase and 90% by weight aqueous phase. 
     The oily phase and the aqueous phase had the following constitution: 
     
         ______________________________________                                    
                     % w/w                                                
______________________________________                                    
Oily phase                                                                
Sorbitan monooleate    20                                                 
Quaternium-18 hectorite                                                   
                       5                                                  
Liquid paraffin        75                                                 
Aqueous phase                                                             
Promoter No. 5         0.5                                                
Xanthan gum            1                                                  
Preservative           0.3                                                
Perfume                q.s.                                               
Sodium chloride (1% w/w solution) to                                      
                       100                                                
______________________________________                                    
 
    
     The emulsion was prepared by taking 10 parts by volume of the oily phase and to it adding slowly with stirring 90 parts by volume of the aqueous phase. 
     The high internal phase water-in-oil emulsion so formed can be applied topically to the scalp, to improve hair growth and regrowth. 
     The following examples 14 to 18 illustrates shampoos for use in washing the hair and scalp, and for promoting hair growth on the scalp. 
     EXAMPLE 14 
     
         ______________________________________                                    
                       % w/w                                              
______________________________________                                    
Sodium lauryl ether sulphate                                              
                         41.4                                             
(2 EO) [21% AD]                                                           
Lauryl dimethylamino acetic acid                                          
                         4                                                
betaine: [30% AD]                                                         
Coconut fatty acid diethanolamine                                         
                         1.5                                              
Oleyl triethoxy phosphate (BRIPHOS 03D)                                   
                         1                                                
Polyglycol-polyamine condensation                                         
                         1.5                                              
resin (POLYQUART H) [50% active]                                          
Preservative, colouring matter, salt                                      
                         0.58                                             
Promoter No. 6           5                                                
Perfume                  q.s.                                             
Water to                 100                                              
______________________________________                                    
 
    
     EXAMPLE 15 
     
         ______________________________________                                    
                     % w/w                                                
______________________________________                                    
Sodium lauryl ether sulphate (2 EO)                                       
                       12                                                 
[100% AD]                                                                 
POLYMER JR400          2.5                                                
BRIPHOS 03D            2.5                                                
Promoter No. 7         4                                                  
Magnesium Sulphate     5                                                  
Perfume                q.s.                                               
Water to               100                                                
______________________________________                                    
 
    
     EXAMPLE 16 
     This Example also illustrates a lotion which is suitable for topical application to the scalp. 
     The lotion has the following formulation: 
     
         ______________________________________                                    
              % w/w                                                       
______________________________________                                    
Promoter No. 8  1.5                                                       
propan-2-ol     10                                                        
ethanol         88.5                                                      
perfume         q.s.                                                      
______________________________________                                    
 
    
     EXAMPLE 17 
     This Example also illustrates a hair tonic which is suitable for application to hair or scalp. 
     The hair tonic has the following formulation: 
     
         ______________________________________                                    
              % w/w                                                       
______________________________________                                    
Promoter No. 8   5                                                        
ethanol         40                                                        
water           50                                                        
perfume         q.s                                                       
______________________________________                                    
 
    
     EXAMPLE 17a 
     This Example also illustrates a hair tonic which is suitable for application to hair or scalp. 
     The hair tonic has the following formulation: 
     
         ______________________________________                                    
              % w/w                                                       
______________________________________                                    
Promoter No. 8  5                                                         
minoxidil       0.5                                                       
ethanol         40                                                        
water           50                                                        
perfume         q.s.                                                      
______________________________________                                    
 
    
     EXAMPLE 18 
     
         ______________________________________                                    
                    % w/w                                                 
______________________________________                                    
Monoethanolamine lauryl sulphate:                                         
                      20                                                  
[100% AD]                                                                 
JAGUAR C13S           3                                                   
BRIPHOS 03D           1.7                                                 
Coconut diethanolamide                                                    
                      5                                                   
Promoter No. 2        1                                                   
Zinc gluconate        3                                                   
Perfume               q.s.                                                
Water to              100                                                 
pH adjusted to 6.5                                                        
______________________________________                                    
 
    
     EXAMPLE 19 
     
         ______________________________________                                    
                     % w/w                                                
______________________________________                                    
Sodium lauryl ether sulphate (3 EO):                                      
                       12                                                 
[100% AD]                                                                 
JAGUAR C13S            0.3                                                
BRIPHOS 03D            1                                                  
Promoter No. 3         2                                                  
Sodium chloride        4                                                  
Perfume                q.s.                                               
Water to               100                                                
pH adjusted to 6.5                                                        
______________________________________                                    
 
    
     EXAMPLE 20 
     
         ______________________________________                                    
                     % w/w                                                
______________________________________                                    
Sodium lauryl ether sulphate (2 EO)                                       
                       12                                                 
[100% AD]                                                                 
POLYMER JR400          3                                                  
BRIPHOS 03D            1                                                  
Opacifier              9                                                  
Promoter No. 4         5                                                  
Perfume                q.s.                                               
Water to               100                                                
pH adjusted to 6.5                                                        
______________________________________                                    
 
    
     EXAMPLES 21 
     This example illustrates a powder composition according to the invention which can be applied topically to the scalp. 
     
         ______________________________________                                    
                % w/w                                                     
______________________________________                                    
Chemically modified                                                       
                  5                                                       
starch                                                                    
Chemically modified                                                       
                  --                                                      
cellulose                                                                 
Boric acid        10                                                      
Zinc oxide        5                                                       
Promoter No. 5    3                                                       
Minoxidil glucuronide                                                     
                  5                                                       
Perfume           q.s.                                                    
Chalk             10                                                      
Talc to           100                                                     
______________________________________                                    
 
    
     EXAMPLE 22 
     The following example illustrates a lotion according to the invention which can be applied topically to the scalp to prevent hair loss and stimulate hair regrowth. 
     
         ______________________________________                                    
                      % w/w                                               
______________________________________                                    
Promoter No. 6          7                                                 
Minoxidil               0.2                                               
ethanol                 16                                                
citric acid             1.05                                              
water to                100                                               
pH adjusted to 4.2 with sodum hydroxide                                   
______________________________________                                    
 
    
     EXAMPLES 23 &amp; 24 
     These examples illustrate hair tonics which are suitable for application to the hair and scalp. 
     The hair tonics had the following formulation: 
     
         ______________________________________                                    
                 % w/w                                                    
                 26   27                                                  
______________________________________                                    
Promoter No. 7      2     --                                              
Promoter No. 8     --      3                                              
ethanol            50     50                                              
water              48     47                                              
perfume            q.s.   q.s.                                            
______________________________________                                    
 
    
     EXAMPLE 25 
     This example illustrates a microgel which is suitable for topical application to hair or scalp. 
     The gel had the following formulation: 
     
         ______________________________________                                    
                     % w/w                                                
______________________________________                                    
A.     Polyoxyethylene (10) oleyl ether                                   
                           14.5                                           
       Polyoxyethylene fatty glyceride                                    
                           14.5                                           
       Light liquid petroleum                                             
                           13.7                                           
       Propylene glycol    7.6                                            
       Sorbitol            5.9                                            
       Promoter No. 1      4                                              
B.     Perfume             q.s.                                           
C.     Water to            100                                            
______________________________________                                    
 
    
     This microgel was prepared by heating part A to 90° C. and part C to 95° C. and then adding part C to part A with stirring. Part B was then added at 70° C. and the final mixture cooled and poured into jars at 55° C. to 60° C. On further cooling, a gel was formed. 
     EXAMPLE 26 
     This example illustrates a shampoo which is suitable for topical application to hair in order to cleanse it, at the same time delivering an inhibitor to the scalp to enhance hair growth or regrowth. 
     The shampoo had the following formulation: 
     
         ______________________________________                                    
                   % w/w                                                  
______________________________________                                    
Triethanolamine lauryl                                                    
                     16.8                                                 
sulphate                                                                  
Coconut diethanolamide                                                    
                     3.0                                                  
Hydroxypropylmethyl- 0.25                                                 
cellulose (1)                                                             
Corn syrup (80% solids) (2)                                               
                     20.5                                                 
Dimethylpolysiloxane (3)                                                  
                     1.0                                                  
Cationic cellulose (4)                                                    
                     0.5                                                  
Ethyl alcohol (SDA 40)                                                    
                     9.0                                                  
Vinyl carboxy polymer (5)                                                 
                     0.75                                                 
Promoter No. 2       1                                                    
Perfume, colour, preservative                                             
                     q.s.                                                 
Water to             100                                                  
Acid or base to pH:  6.5                                                  
______________________________________                                    
 (1) Methocel E4M (Dow Chemical)                                          
 (2) 42 Dextrose equivalent (Staley 1300)                                 
 (3) 60,000 centistokes (Viscasil, GEC)                                   
 (4) Polymer JR 400                                                       
 (5) Carbopol 941 (BF Goodrich)                                           
 
    
     EXAMPLES 27 to 28 
     The following formulations represent lotions which can be used topically in the treatment of bald or balding male or female heads. 
     
         ______________________________________                                    
                 % w/w                                                    
                 27    28                                                 
______________________________________                                    
Hydroxyethyl cellulose                                                    
                   0.4     --                                             
Absolute ethanol   25      25                                             
Propane-1,2-diol   --      --                                             
Butane-1,3-diol    38.4    38.8                                           
Paramethyl benzoate                                                       
                   0.2     0.2                                            
Promoter No. 3     5       --                                             
Promoter No. 4     --      1                                              
Perfume            1       1                                              
Water to           100     100                                            
______________________________________