A METHOD FOR STIMULATING HAIR GROWTH WITH CATIONIC DERIVATIVES OF MINOXIDIL USING THERAPEUTIC IONTOPHORESIS

Abstract: This invention relates to a method of applying a cationic derivative of Minoxidil which is transported by means of iontophoresis to hair follicles where the cationic derivatives promote hair growth. Each of the cationic derivatives of Minoxidil are synthesized by reacting the Minoxidil parent compound with an organic or an inorganic acid to form the cationic derivative.

Description: A METHOD FOR STIMULATING HAIR GROWTH WITH CATIONIC DERIVATIVES OF MINOXIDIL USING THERAPEUTIC IONTOPHORESIS BACKGROUND OF THE DISCLOSURE FIELD OF THE INVENTION: This invention relates to an improved method of application of Minoxidil to stimulate hair growth by means of iontophoretic transport to the hair follicle after converting Minoxidil to an ionic form. BACKGROUND OF THE INVENTION: The patent literature is replete with compositions and processes for stimulating mammalian hair growth and/or keratin formation. Of these, Minoxidil (6-piperidino-2,4-diaminopyrimidine-3-oxide) is a drug which has been found to be useful in promoting hair growth. Minoxidil is normally applied as an active ingredient topically to the area where hair growth is desired. U. S. Patent 4,970,063 describes and defines compositions and methods using what is defined as "Minoxidil," said patent being incorporated herein by reference. Other U.S.A. patents which teach the use of Minoxidil for hair growth are 3,461,461; 3,910,928; 4,139,619; and 4,596,812. It is believed that Minoxidil promotes hair growth after diffusion to the hair follicles. The precise site and mechanism of action have not as yet been elucidated. Although Minoxidil is effective in promoting hair growth after it reaches the hair follicle, the clinical efficacy of topical application is limited by low water solubility and by the fact that the outer layers of skin are an effective barrier to penetration of polar molecules such as Minoxidil. The technique of iontophoresis employs a small electric current to transport ionic drug compounds into the skin or other tissue. Iontophoresis is believed to increase drug entry through so-called "shunt pathways" provided by hair follicles and sweat glands. Since hair follicles are a major pathway for iontophoretic drug delivery, iontophoresis is potentially the ideal method of administering Minoxidil to the hair follicles. Water is the preferred solvent for use in iontophoresis. Minoxidil itself has a low solubility in water and, because it has no net ionic charge, does not migrate in an iontophoretic field. In fact, due to the dipolar nature of Minoxidil, there is some evidence that the iontophoretic field inhibits even the passive migration by electro- osmosis often observed with non-charged compounds in electric fields. Thus, although Minoxidil is effective in promoting hair growth after it reaches the hair follicles, presently there has been no therapeutic delivery system that utilized a transport mechanism other than passive diffusion in its attempt to deliver Minoxidil across the skin's membrane barrier to the hair follicle. SUMMARY OF THE INVENTION The present invention is directed to the application of ionic derivatives or salts of Minoxidil which can effectively be transported via iontophoresis to hair follicles where they promote hair growth. Specifically, the invention is directed to the cationic derivatives of Minoxidil, such as taught in the aforesaid U. S. Patent 4,970,063, which are purified and then applied in an electric conductive solution, usually aqueous, to the area where hair growth is desired and transported to the hair follicles by means of iontophoresis. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The term "Minoxidil" as used herein refers to the compound 6-(1 -piperidinyl)-2,4- pyrimidinediamine 3-oxide (the uninverted name used by Chemical Abstracts Service during the ninth and/or subsequent Collective Index Periods and having the Chemical Abstracts Registry Number [38304-91-5]). The Merck Index, Eleventh Edition (published by Merck & Co., Inc., Rathway, N.J., U.S.A., 1989) lists a number of other names, including6-piperidino-2,4-diaminopyrimidine3-oxideand6-amino-1,2-dihydro-1- hydroxy-2-imino-4-piperidinopyrimidine, one of the tautomers of Minoxodil. Reference is also made to U. S. Patents 4,970,063 and 3,461,461. Ionic specifically cationic derivatives of Minoxidil are formed according to a preferred embodiment of the present invention by means such as set forth in the following general procedure. GENERAL PROCEDURE FOR CREATING IONIC DERIVATIVES OF MINOXIDIL A solution of 4.2 g (0.02 mole) of Minoxidil (6-piperidino-2, 4-diaminopyrimidine- 3-oxide) in 100 ml of 95% alcohol at about 70°C is placed in a 500 ml three-necked flask equipped with a reflux condenser, stirrer and a dropping funnel. The stoichiomet- ric amount of an organic acid (0.01 mole of d-tartaric acid or 0.02 mole of one of the other acids listed below) dissolved in 100 ml of 95% ethanol at a temperature of about 70 >C was placed in the dropping funnel and added to the stirred Minoxidil solution in a dropwise fashion over a period of about one hour. Upon completion of the addition, the reaction mixture is stirred, for from 16 to 24 hours, while being maintained at a temperature of about 70<>C. Any significant amount of solid present is removed by filtration. The remaining solution is transferred to a 500 ml one-necked flask and concentrated to about 50 ml under reduced pressure using a Roto Vac device. The precipitates formed are collected by vacuum filtration and purified by recrystallization from absolute alcohol. Seven prototype salts or cationic derivatives were prepared using the general procedure. The salt obtained from the reaction with 5-nitro-2-furoic acid was bright yellow in color; all other compounds were white solids. The salts were characterized by their melting points, elemental analyses, infrared spectra, proton NMR spectra and carbon 13 NMR spectra. The percentage yields, melting points and elemental analyses are summarized in Table I. TABLE I ORGANIC ACID MOLECULAR % MELTING ELEMENTAL ANALYSIS REACTANT FORMULA OF YIELD POINT, °C PRODUCT %C %H %N [R-(R*,R*)]-2,3- CggHggN^Og 87% 212-214 Theory 47.14 6.47 24.99 dihydroxy-butan- edioc acid (d-tar- Found 46.48 6.19 24.46 taric acid) 2,4,6(1 H.3H.5H)- Cι 3 H 19 N 7 0 4 86% 198-200 Theory 46.29 5.68 29.06 pyrimidinet one (barbituric acid) Found 45.05 5.77 28.16 3,4-dihydroxy- Cι 6 H 21 N 5 0 5 89% 212-214 Theory 52.89 5.83 19.27 benzoic acid (protocatechuic Found 52.49 5.96 22.37 acid) 2,3,4-trihydroxy- C 16 H 21 N 5°6 62% 226-228 Theory 50.66 5.58 18.46 benzoic acid Found 50.22 5.57 20.13 3,4,5-trihydroxy- Cι 6 H 2 ιN5°6 85% 211-212 Theory 50.66 5.58 18.46 benzoic acid (gallic acid) Found 50.63 5.84 21.82 5-nitro-2-furoic C 14 H 18 N6θ 6 55% 226-228 Theory 45.90 4.95 22.94 acid Found 45.81 4.82 22.84 5,5-dimethyl- C 14 H22N 6 0 4 65% 165-167 Theory 49.70 6.55 24.84 oxazolidine-2,4- dione Found 50.21 6.68 26.16 (dimethadione) Equations for the reactions of Minoxidil with the seven organic acids listed in Table 1 are listed below. Equations for the reactions of Minoxidil with various acids (barbituric acid) (protocatechuic acid) 2,3,4-trihydroxybenzoic acid 3,4,5-trihydroxybenzoic acid (gallic acid) The cationic derivatives of Minoxidil are not limited to those produced by the seven acids which are listed but may be produced with other organic and inorganic acids. IONTOPHORETIC TRANSPORT OF CATIONIC DERIVATIVES OF MINOXIDIL The transdermal iontophoresis of cationic derivatives of Minoxidil was demonstrated in laboratory experiments utilizing fresh, full-thickness mouse skin with clipped hair, which has been reported to be an excellent model for studying the drug permeability of human skin. Iontophoresis was conducted with side-by-side diffusion cells obtained from the Crown Glass Co. A piece of mouse skin was clamped between the two half-cells, and the donor cell was filled with an aqueous solution of one of the ionic derivatives of Minoxidil. The receiver cell was filled with 0.05 molar sodium chloride solution. An electric current was applied across the two half-cells using silver/silver chloride electrodes inserted into both cells through teflon plugs. The donor cell electrode was always the anode (positive pole +) except where otherwise noted. An electric stimulator was used to apply a 0.8 milliamp, current to a diffusion area of 0.64 cm 2 for periods of up to 90 minutes, and the iontophoretic mobility of the ionic derivatives of Minoxidil was determined by sampling the receiver cell compartment at various times throughout the study. The concentration of cationic derivatives of Minoxidil in the receiver cell was measured by ultraviolet spectrophotometry. Data was also obtained under passive conditions without any electric current. The results of 4 to 8 separate experiments with each Minoxidil ionic derivative were used to calculate the average flux for passive and active iontophoretic conditions and these data are shown in Table 2 below. Iontophoresis significantly enhanced the skin permeation of the Minoxidil ionic derivatives. The Minoxidil tartrate derivative of those tested showed significant improvement in iontophoretic mobility across the skin. These results demonstrate that iontophoresis can be used to enhance the delivery of Minoxidil to the skin. TABLE 2 Active (Iontophoretic) and Passive Flux (ug/cm 2 /h) of Minoxidil Ionic Derivates 1 MINOXIDIL IONIC 5-30 MINUTES 30-90 MINUTES 5-90 MINUTES DERIVATES 2 Dimethadione 0.1% ACTIVE 68.6 ±. 10.3 136.0 _± 19.8 95.8 ±. 13.3 PASSIVE 25.7 _± 5.5 25.8 ±. 2.4 17.2 _± 1.6 Dimethadione 0.2% ACTIVE 74.0 ±. 15.3 146.6 _+ 9.9 97.7 ±. 6.6 PASSIVE 34.9 ± 5.8 29.2 _± 1.7 19.5 ±-. 1.2 Tartrate 0.1% ACTIVE 65.4 ±. 19.4 189.7.± 36.2 144.6 ± 23.0 PASSIVE 59.2 _± 17.6 25.6 ±. 6.2 29.6 ±. 6.6 Tartrate 0.2% ACTIVE 74.3 _± 21.8 180.4 _± 26.7 140.9 ± 22.7 PASSIVE 23.3 _± 4.7 20.6 _± 6.8 20.2 ^ 5.8 Trihydroxybenzoate 0.1% ACTIVE 37.2 _+ 5.8 62.4 _± 9.9 59.7 ±. 7.8 PASSIVE 24.7.± 4.3 24.5.± 3.4 21.9 _± 3.6 Trihydroxybenzoate 0.2% ACTIVE 53.2 ±. 5.6 173.9 ±. 29.0 115.9 _± 19.4 PASSIVE 4.3 _+ 1.9 6.0 ±. 1.8 4.0 ± 1.2 1 Values are the mean and standard error of 4 to 8 separate studies. 2 The terminology for the derivatives is expressed as the common name for the acid used and the concentration is expressed as percentage of Minoxidil base. In practice, one method of practicing the invention is to mix the cationic derivative salt of Minoxidil as a distilled water solution in proportion of 0.1 mg/ml to a saturated solution. An iontophoretic device such as manufactured and sold by General Medical Co. under the registered mark LECTRO PATCH would be used. Both treatment pads are saturated with the Minoxidil salt solution. The saturated treatment pads are placed on the skin where enhanced growth is desired. This particular device will only accept up to 1 milliamp (mA) of current. Other iontophoretic devices, such as New Life Litronic Stimulator manufactured by Mid-western Electronics Inc. Model No. 0880 can deliver up to .5 mA per cm 2 can also be used. The tolerance of an individual patient determines time and milliamp limits above .5 mA per cm 2 . While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiment set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claimed or claims, including the full range of equivalency to which each element thereof is entitled.

Claims: CLAIMS What is claimed is: 1. A pharmaceutically acceptable composition useful in promoting mammalian hair growth when applied using iontophoresis comprising a) a cationic derivative of Minoxidil in solution. 2. The composition according to claim 1 wherein the cationic derivative of Minoxidil is derived by mixing solutions of Minoxidil with an organic acid selected from the group consisting of: [R-(R*,R*)]-2,3-dihydroxybutanedioic acid (also known as d-tartaric acid); 2,4,6(1 H,3H,5H)-pyrimidinetrione (also known as barbituric acid); 3,4-dihydroxybenzoic acid (also known as protocatechuic acid); 2,3,4-trihydroxybenzoic acid; 3,4,5-trihydroxybenzoic acid (also known as gallic acid); 5-nitro-2-furoic acid; and 5,5-dimethyloxazolidine-2-4-dione (also known as dimethadione). 3. The composition according to claim 2 wherein the solutions are mixed at 70< C. 4. The composition according to Claim 2 wherein the solutions are mixed and stirred for up to 24 hours. 5. A method of promoting hair growth on skin of a human or animal comprising the steps of applying a pharmaceutically effective amount of a cationic derivative of Minoxidil to said skin, and applying safe electric current to the skin sufficient to create iontophoresis to transport said cationic derivative of Minoxidil to the hair follicles. 6. The method of claim 5 wherein said cationic derivative of Minoxidil is produced by the steps of: a) mixing a solution of Minoxidil with a solution of organic acid at an elevated temperature for a period of time sufficient to form a precipitate b) collecting and purifying the precipitate so the precipitate can be used in iontophoresis. 7. The method of claim 6 wherein said organic acid solution contains an organic acid selected from the group consisting of: [R-(R*,R*)]-2,3-dihydroxybutanedioic acid (also known as d-tartaric acid); 2,4,6(1 H,3H,5H)-pyrimidinetrione (also known as barbituric acid); 3,4-dihydroxybenzoic acid (also known as protocatechuic acid); 2,3,4-trihydroxybenzoic acid; 3,4,5-trihydroxybenzoic acid (also known as gallic acid); 5-nitro-2-furoic acid; and 5,5-dimethyloxazolidine-2-4-dione (also known as dimethadione). 8. The method according to claim 6 wherein the two solutions are mixed at a temperature substantially within the range of 60°C to 80°C, preferably 70°C and stirred for up to 24 hours. 9. The method of claim 5 wherein said cationic derivative of Minoxidil is produced by the steps of: a) mixing a solution of Minoxidil with a solution of inorganic acid at an elevated temperature for a period of time sufficient to form a precipitate b) collecting and purifying the precipitate so the precipitate can be used in iontophoresis. 10. In a method of promoting mammalian hair growth by using a cationic derivative of Minoxidil in pharmaceutically effective solutions the improvement comprising the use of safe electrical current to create iontophoresis. 11. A pharmaceutically effective topical composition for promoting hair growth in humans using iontophoresis, said composition comprising a pharmaceutical solution of a cationic Minoxidil derivative. 12. A pharmaceutically effective topical composition for promoting hair growth in humans using iontophoresis, said composition comprising a pharmaceutical solution of Minoxidil tartrate possessing a superior water solubility. 13. A pharmaceutically effective topical composition for promoting mammalian hair growth comprising a polar N-oxide compound that has been converted to a cationic derivative and capable of transport into hair follicles by iontophoresis. 14. A pharmaceutically effective topical composition for human non-invasive treatment comprising a polar N-oxide compound that has been converted to a cationic derivative and capable of transport into hair follicles by iontophoresis. 15. A method of human treatment comprising the application of a pharmaceutically effective polar N-oxide compound, that has been converted to a cationic derivative, for non-invasive therapeutic transport using iontophoresis.

Inventors: ALLEN LOYD V JR, BRENNER GEORGE M, HUERTA PEDRO L JR, POULOS CHARLES W, PRABHU VILAS A, ALLEN, LOYD, V., JR., BRENNER, GEORGE, M., HUERTA, PEDRO, L., JR., POULOS, CHARLES, W., PRABHU, VILAS, A.
Applicants: TULSA FORTE PHARMACY ENTERPRIS, TULSA FORTE PHARMACY ENTERPRISES, INC.
Application year: 1993
Main classification: A61K7
IPC codes: A61K8, A61K31, A61N1, A61Q5, A61Q7, C07D239