WO2006002096A2

WO2006002096A2 - Low doses of l-citrulline for treating diseases

Info

Publication number: WO2006002096A2
Application number: PCT/US2005/021811
Authority: WO
Inventors: Albert Cha; Edgar G. Engleman
Original assignee: Vivo Therapeutics, Inc.
Priority date: 2004-06-18
Filing date: 2005-06-16
Publication date: 2006-01-05
Also published as: WO2006002096A3

Abstract

The present invention is directed to a method of treating vascular diseases, sexual dysfunction, or infertility. The method comprises administering to a subject a composition comprising an effective amount of L-citrulline of less than 1.7 g/day. The composition is a pharmaceutical composition or a nutraceutical composition. Low doses of L-citrulline can be used in conjunction with other therapeutic agents commonly used to treat disorders.

Description

LOW DOSES OF L-CITRULLINE FOR TREATING DISEASES

FIELD OF THE INVENTION The present invention relates to treating a human subject suffering from vascular disease, infertility, or sexual dysfunction with low doses of L-citrulline.

BACKGROUND OF THE INVENTION L-arginine is a substrate of the enzyme nitric oxide synthase (NO synthase), which converts L-arginine to L-citrulline and produces nitric oxide, a gaseous molecule that causes endothelial relaxation and improved vascular function. L-arginine has been studied for the treatment of vascular diseases such as nitrate tolerance, where it was used in conjunction with transdermal nitroglycerin at a dose of 2.8 g/day to prevent nitrate tolerance (J.O. Parker et al., J Am Coll Cardiol. 2002 Apr 3;39(7):1199-203). L-arginine has been studied for the treatment of peripheral arterial disease, where it was used alone at a dose of 16 g/day to improve pain with walking (R.H. Boger et al., J Am Coll Cardiol. 1998 Nov;32(5): 1336-44). L-arginine has been used for the treatment of infertility at a dose of 16 grams/day (C. Battaglia et al., Hum Repro 199, 14(7): 1690-1697), and for the treatment of male and female sexual dysfunction, where it was used in combination with other active ingredients at a dose of 2.5-3 grams/day (T. Ito et al., Hawaii Med J. 1998 Dec;57(12):741-4; T. Ito et al., J Sex Marital Ther. 2001 Oct-Dec;27(5):541-9). The large dose of L-arginine, at or exceeding 2.4 grams per day, is difficult to obtain reasonable compliance from subjects, either as a nutraceutical or pharmaceutical formulation. Human subjects have difficulty maintaining compliance with ingesting more than a certain number and size of tablets per day. Administering large amounts of L-arginine, on the order of 2.4 grams a day or more, typically requires very large tablets (1 gram or larger). These tablets are difficult to swallow, particularly for subjects who are not used to swallowing large pills, and can cause unpleasant sensations as the pills move down the digestive tract. Such effect reduces the compliance of subjects who take the product, and can cause subjects to stop taking the product. In addition, given a large dose of L-arginine that must be given, subjects must take several large pills a day to achieve the minimum level of efficacy. This further reduces compliance of subjects because of the subject's refusal to take multiple large pills on a daily basis. L-arginine, when taken orally, has a relatively short plasma half-life of approximately an hour (W.E. Smoyer et al., J. Lab. Clin. Med. 118: 166-175, 1991). The short half-life of L-arginine is due to the first-pass metabolism of L-arginine that occurs in the liver with hepatic arginases, as well as circulating plasma arginase that degrades the L-arginine during its systemic circulation after absorption. Optimal efficacy of systemic L-arginine results from consistently increased plasma levels. However, because of L-arginine 's short half-life, a subject must take L-arginine four to six separate times a day in order to achieve an optimal efficacy. Multiple dosing also creates significant compliance issues for a subject, since many subjects will not take pills every 4 hours. L-arginine has been demonstrated to be efficacious for the treatment of peripheral arterial disease in human subjects at the dose of 2 x 8 grams a day (R.H. Boger et al., J. Am. Coll. Cardiol. 1998; 32:1336-44). However, such dosage would require the ingestion of at least 16, preferably 20 capsules a day of L-arginine, which is not an acceptable formulation and produces significant compliance issues for human subjects. L-arginine has been demonstrated to be efficacious for the prevention of nitrate tolerance in human subjects at the dose of 2.8 grams per day, with 4 large tablets being given every 6 hours (J.O. Parker et al., J. Am. Coll. Cardiol. 2002; 39:1199-203). However, taking four large tablets every six hours is not an acceptable formulation and has significant compliance issues. L-arginine has been demonstrated to be efficacious, in combination with ginkgo and ginseng and other vitamins and minerals, effective for the treatment of sexual dysfunction in both males and females (T. Ito et al., Hawaii Med J. 1998; 57:741-4; T. Ito et al., J. Sex. Marital Ther. 2001; 27(5): 541-9). However, the L-arginine doses used were in the range of 2.5 grams to 3 grams a day, taken as 6 large capsules a day. Again, taking six tablets a day is not an acceptable formulation and has significant compliance issues. L-arginine has been demonstrated to be efficacious for the treatment of female infertility in patients undergoing in vitro fertilization (C. Battaglia et al., Hum. Repro. 1999, 14(7): 1690-7). The L-arginine doses used were approximately 16 grams per day. L-arginine at doses of 4 to 20 grams per day has also been shown efficacy in treating improving total sperm counts and motility rates of spermatocytes in infertile men (A. Schachter et al., J. Urol, 110: 311-313, 1973). L-arginine has shown efficacy in improving cerebrovascular disease by decreasing infarct size caused by a stroke in rats, at a dose that for a normal 70-kg person would be 21 g/day (Morikawa et al., Am. J. Physiol, 2563: H1632-H1635, 1992). L-arginine has shown benefit in atherosclerotic disease at doses of 10 mg/kg/min for 20 minutes, which would be 14 grams for a normal 70-kg subject (J.P. Cooke et al., J. Clin. Invest. 90: 1169-1172, 1992). L-citrulline is a non-essential amino acid that has been described as a dietary supplement. Doses of L-citrulline on the order of 0.1 g/kg per day, or 7 g for an average human of 70 kg in weight, improved the well-being of patients with sickle cell disease (W.H. Waugh et al., J. National Medical Assoc, 93(10), 363-371, 2001). In this study, L-citrulline also increased plasma L-arginine levels and showed a trend in reducing total leukocyte counts in patients with sickle cell disease. L-citrulline dosed in normal volunteers at 3.8 g/m (yielding a dose of approximately 11 grams for an average human of 66 inches in height) demonstrated increased plasma L- arginine levels (Kuhn, et al "Oral Citrulline Effectively Elevates Plasma Arginine Levels for 24 Hours in Normal Volunteers"). At these large doses typically exceeding 6 grams a day, the large dose of citrulline also yielded a higher systemic bioavailability than an equimolar dose of L-arginine. The total plasma arginine above baseline generated by oral L-citrulline was 1440 μM-hrs, vs. 476 μM-hrs for the equimolar dose of oral L-arginine. L-arginine plasma levels were still 32% above baseline 24 hours after oral L-citrulline administration, whereas plasma L-arginine levels went back to baseline within 5 hours of oral L-arginine. U.S. Patent Nos. 5,874,471 and 6,028,107(Waugh) discloses a method of improving the health of a subject to increase the plasma level of arginine in the subject to a level from a low or normal fasting level to a level which is up to three times an average overnight fasting level, comprising orally administering a substance of L-citrulline or the calcium salt of L- citrulline. Both references are incorporated herein by reference in their entirety. U.S. Patent Application Publication 2001/0056068 (now abandoned) disclosed method of treatment of some nitric oxide deficiency-related disorders using citrulline. In order to have oral doses of several grams of L-citrulline per day, patients must take at least three large pills a day. Large pills can be difficult to swallow, and taking several at once is not desirable. There is a need of a method of treating various diseases using low doses of citrulline; such method is effective, and easy for patients to comply. SUMMARY OF THE INVENTION The present invention is directed to a method of treating a human subject suffering from vascular disease, sexual dysfunction, or infertility. The method comprises the step of administering to a subject a composition comprising a therapeutically effective amount of L- citrulline, wherein the therapeutically effective amount is less than 1.7 g per day. This composition can be either a pharmaceutical or nutraceutical composition comprising a therapeutically effective amount of L-citrulline and a pharmaceutically acceptable carrier or nutraceutically acceptable carrier. The composition is administered to a subject by oral, intravenous, topical, rectal, or vaginal route, with oral being a preferred route. The composition is administered in a form selected from the group consisting of: capsule, tablet, and liquid.

DETAILED DESCRIPTION OF THE INVENTION The applicants discover that low doses (<1.7 g per day) of L-citrulline are efficacious for treating sexual dysfunction, vascular diseases, infertility; and improving health. The method comprises administering to a human subject a composition comprising a therapeutically effective amount of L-citrulline of up to 1.7 grams per day. A therapeutically effective dose of L-citrulline often elevates L-arginine level in a target organ and/or plasma or serum, and is effective to treat diseases. Oral L-arginine has a relatively short half-life in human plasma of 80 minutes (Bode- Boger Sm, et al., Br. J. Clin. Pharmacol. 46:489-97 (1998)), which suggests an optimal dosing of L-arginine of every 4-6 hours, or four to six times a day, with which human subjects often have difficulties maintaining compliance. The applicants have discovered that oral L- citrulline has a half-life on the order of 6 to 8 hours. Because of the low dose and long half- life, citrulline can be given in smaller pills and much less frequently such as once or twice a day, which significantly improves patient compliance while maintaining an optimal biological activity of plasma L-arginine for human subjects. Low doses of L-citrulline are beneficial in treating a number of different diseases. Low doses of L-citrulline are beneficial in treating vascular disease, which includes but is not limited to peripheral arterial disease, nitrate tolerance, sickle cell disease, pulmonary hypertension, coronary artery disease, cerebrovascular disease, and migraine headache. Peripheral arterial disease causes patients suffering from the disease to experience pain in the affected limbs, during exercise, walking, or even at rest. Nitrate tolerance is defined as the wearing off of the clinical effect of nitrates, which comprise nitroglycerin, isosorbide mononitrate, and isosorbide dinitrate, after the nitrates have being given continuously for a period of time of no less than 48 hours. Low doses of L-citrulline are particularly useful in treating peripheral arterial disease, sickle cell disease, and migraine headache Low doses of L-citrulline are beneficial for treating sexual dysfunction, which includes but is not limited to erectile dysfunction, sexual arousal disorders, orgasmic disorders, and sexual pain disorders (including vaginismus and dyspareunia). As used herein, the term "sexual dysfunction" means a medical diagnosis according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, (DSM-IV), Washington DC, American Psychiatric Association, 1996, which includes the criteria, types, disorders, and subtypes of sexual dysfunction listed therein. Erectile dysfunction arises from the patient's ability to have or maintain an erection. Sexual arousal disorders arise from the patient's inability to become sexually aroused. Orgasmic disorders arise from the patient's inability to experience orgasm or sexual climax during sexual intercourse. Sexual pain disorders arise from subjects experiencing pain during intercourse such that it interferes with normal coitus. Low doses of L-citrulline are effective in treating various components of sexual dysfunction, including improvement of erectile dysfunction, increasing frequency of intercourse, improving vaginal dryness, increasing frequency of orgasm, increasing degree of penile sensation, increasing frequency and level of sexual desire, or satisfaction with overall sex life. It is particularly effective when given with ginseng extracts and/or ginkgo biloba extracts. Various types of ginseng are available on the commercial market and are available from various sources, such as, for example, East Earth Herb and Natural Sourcing Solutions, Inc. The types and relative abundance of the chemical constituents of ginseng depend on the species, the part of the plant, the place of origin, the method of cultivation, and the technique of extraction used to obtain the ginseng. Various types of ginseng are useful in combination with L-citrulline for treating sexual dysfunction. Preferred materials are extracted from Panax ginseng or Panax quinquefolius. In one embodiment, a mixture of American ginseng and Korean ginseng is employed. Ginseng composition extracted from the roots of various plants are similar. Generally, ginseng contains ginsenosides. A further discussion of the constituents of various types of ginseng can be found in the American Chemical Society publication entitled "Folk Medicine: The Art and the Science," edited by Richard P. Steiner, University of Utah (1986). Ginkgo biloba is extracted from the leaves of the ginkgo biloba tree. The leaves are harvested in late summer when the leaves have the highest level of active compounds. Ginkgo biloba extract is partially purified to remove undesirable compounds that do not contribute to the desired health benefits. Ginkgo biloba extract can be highly concentrated and standardized to a known and consistent level of the active principals known as ginkgolides. Ginkgo biloba is readily available from various sources throughout the herbal medicine industry; for example, East Earth Herb and Natural Sourcing Solutions, Inc. Low doses of L-citrulline are useful for treating male infertility. Male infertility is typically caused by deficiencies in the sperm produced by the male, in the number of sperm, the motility of sperm, and/or the linearity of the sperm (ability for the sperm to move in a straight line). Low doses of L-citrulline are effective in treating male infertility by improving sperm count, linearity, and/or sperm motility. Low doses of L-citrulline are particularly effective when given in combination with L-carnitine, an amino acid that promotes formation of healthy sperm. Low doses of L-citrulline are useful for treating female infertility. Female infertility has multiple etiologies. Treating female infertility includes improving the likelihood of successful pregnancies carried to term. Treating female infertility also includes improving uterine perfusion and follicular formulation, which improves probability of successful implantation by the fertilized egg. Low doses of L-citrulline are particularly effective when given in combination with extracts of Vitex agnus castus (chasteberry), and/or green tea extracts. Chasteberry is also known as Agnus Castos, Chaste Tree, Hemp Tree, Monk's Pepper. Its scientific name is Vitex Agnus Castus from the family Verbenacaea. Chasteberry has been used orally for the reduction of menopausal symptoms. Chasteberry is antiandrogenic. Chasteberry enhances hormone balance by increasing progesterone release and ovulation frequency. Green tea is also known as Chinese tea. Its scientific name is Camellia Sinensis, Camellia Thea, Camellia Theifera, Thea Sinensis, Thea Bohea, or Thea Viridis from the family Theaceae. The useful parts are the leaf bud, leaf and stem. Green tea improves overall reproductive health and contains anti-oxidants beneficial to cellular viability. Low doses of L-citrulline are beneficial in improving health. The effects of low doses L-citrulline are seen throughout the body. For example, low doses of L-citrulline improve blood flow, which leads to improved vascular compliance and exercise tolerance in subjects that are in good health as well as subjects affected by vascular diseases. Low doses of L-citrulline can optimize male and female sexual health by improving lubrication, erection, libido, desire, satisfaction, and orgasm. Low doses of L-citrulline can also optimize male and female reproductive health by improving probability of successful fertilization and pregnancy, as well as quality and quantity of sperm count. Low doses of L-citrulline can be formulated as a pharmaceutical composition or a nutraceutical composition comprising a therapeutically effective amount of L-citrulline and other suitable excipients. Nutraceutical compositions (nutraceuticals) are a general term used to describe dietary supplements that are regulated by the FDA under the Dietary Supplement Health and Education Act of 1994 (DSHEA), which was passed to regulate dietary supplements separately from foods. Nutraceuticals include vitamins, minerals, herbs or other botanicals, amino acids, dietary substances such as enzymes, metabolites, constituents, extracts, concentrates, and combinations of the preceding types of ingredients. Dietary supplements may be found in many forms, such as tablets, capsules, liquids, or bars. Nutraceuticals are not subject to pre-market safety evaluations required for new food ingredients or for new uses of old food ingredients, but they must meet the requirements of safety provisions. Once the FDA has been notified regarding a specific nutraceutical under DSHEA, the product can be marketed directly to the U.S. consumer. The pharmaceutical composition of the present invention comprises a therapeutically effective amount of L-citrulline and a pharmaceutically acceptable carrier. The nutraceutical composition of the present invention comprises a therapeutically effective amount of L- citrulline and a nutraceutically acceptable carrier. The composition of the present invention contains L-citrulline as the active ingredient in an amount of 0.5% by weight or more, preferably 10 to 90% by weight, based on the total weight of the composition. These compositions optionally contain other therapeutically active compounds. The composition of the present invention encompasses non- toxic acceptable salts of L-citrulline, including but not limited to, alkali metal salts such as lithium, sodium or potassium salts, or alkaline earth metal salts such as magnesium or calcium salts; or ammonium or mono-, di-, tri- or tetraalkyl ammonium salts, such as NH₄ ⁺, NLH₃ ⁺, NL₂H₂ ⁺, NL₃H⁺, or NL₄ ⁺ (wherein L is Ci_-4 alkyl) salts. Acceptable salts are salts that retain the desired biological activity of the parent compound and do not impart undesired toxicological effects. The compositions of the present invention can be applied by any of the accepted modes of systemic administration including oral, parenteral, rectal, and otherwise systemic routes of administration. Any pharmaceutically acceptable form can be used, including solid, semi-solid, or liquid dosage forms, such as for example, tablets, suppositories, pills, capsules, powders, liquids suspensions, or the like, preferably in unit dosage form suitable to single administration of precise dosages, or in sustained or controlled release forms for the prolonged administration of the compound at a predetermined rate. The compositions typically include a conventional pharmaceutical carrier or excipient and the drug product L- citrulline as well as pharmacologically acceptable salts and optionally include other medicinal agents, pharmaceutical agents, carriers, etc. The compositions are advantageously compounded into unit dosage forms, containing a predetermined, standard amount of the active compound, to make dosing and patient compliance simpler. Any nutraceutically acceptable form can also be used, including solid, semi-solid, or liquid dosage forms such as tablets, pills, capsules, bars, powders, liquid suspensions, or the like. The amount of active compound (L-citrulline) administered depends on the subject being treated, the severity of the affliction, the manner of administration, and the judgment of the prescribing physician. The effective dose of the present invention is less than 1.7 g/day. In one embodiment, an effective dosage of L-citrulline is in the range of 250 to 1600 mg/day. In another embodiment, an effective dosage is in the range of 500, 750, or 1000 to 1600 mg/day. In another embodiment, an effective dosage is in the range of 500, 750, or 1000 to 1500 mg/day. These doses may be administered all at a time or in divided doses. The dosage of these compounds may vary in accordance with the administration route, the age of the patient and the degree of the therapeutic effect desired. Pharmaceutical carriers or nutraceutical carriers useful for the present invention include all organic or inorganic carrier materials that are usually used for the pharmaceutical or nutraceutical preparations, and are inert to the active ingredient. Examples of carriers suitable for the preparation of tablets capsules, granules and fine granules are diluents such as lactose, starch, sucrose, D-mannitol, calcium sulfate, or microcrystalline cellulose; disintegrators such as sodium carboxymethylcellulose, modified starch, or calcium carboxymethylcellulose; binders such as methylcellulose, gelatin, acacia, ethylcellulose, hydroxypropylcellulose, or polyvinylpyrrolidone; lubricants such as light anhydrous silicic acid, magnesium stearate, talc, or hydrogenated oil; or the like. When formed into tablets, they may be coated in a conventional manner by using the conventional coating agents such as calcium phosphate, carnauba wax, hydroxypropyl methylcellulose, macrogol, hydroxypropyl methylphthalate, cellulose acetate phthalate, titanium dioxide, sorbitan fatty acid ester, or the like. Examples of carriers suitable for the preparation of syrups are sweetening agents such as sucrose, glucose, fructose, or D-sorbitol; suspending agents such as acacia, tragacanth, sodium carboxymethylcellulose, methylcellulose, sodium alginate, microcrystalline cellulose, or veegum; dispersing agents such as sorbitan fatty acid ester, sodium lauryl sulfate, or polysorbate 80; or the like. When formed into syrups, the conventional flavoring agents, aromatic substances, preservatives, or the like may optionally be added thereto. The syrups may be in the form of dry syrup that is dissolved or suspended before use. Examples of bases used for the preparation of suppositories are cacao butter, glycerin saturated fatty acid ester, glycerogelatin, macrogol, or the like. When formed into suppositories, the conventional surface active agents, preservatives or the like may optionally be admixed. When formed into injections, the compound is dissolved in distilled water for injection, to which may optionally be added the conventional solubilizers, buffering or pH adjusting agents, isotonic agents, preservatives and other suitable substances. The injections can be in the solid dry preparations, which are dissolved before use. For solid compositions, conventional non-toxic carriers such as mannitol, lactose, starch, magnesium stearate, sodium saccharin, talcum, cellulose, glucose, sucrose, magnesium carbonate, and the like may be used. The active compound may be formulated as suppositories using, for example, polyalkylene glycols, for example, propylene glycol as a carrier. Liquid compositions can, for example, be prepared by dissolving, dispersing, etc. an active compound as defined above and optional adjuvants in a carrier, such as, for example, water, saline, aqueous dextrose, glycerol, ethanol, and the like to thereby form a solution or suspension. If desired, the composition may also contain minor amounts of non- toxic auxiliary pH buffering agents and the like, for example, sodium acetate, sorbitan monolaurate, triethanolamine oleate, etc. Methods of preparing such dosage forms are known to those skilled in this art; for example, see Remington's Pharmaceutical Sciences, Mack Publishing Company, Easton, Pa., 15th Edition, 1975. Dosage forms or compositions containing active ingredient in the range of 0.25 to 95% with the balance made up from non-toxic carrier may be prepared. For oral administration, an acceptable non-toxic composition is formed by the incorporation of any of the normally employed excipients, and may contain l%-95% active ingredient, preferably 5%-90%. Parenteral administration is generally characterized by injection, whether subcutaneously, intramuscularly, or perineurally. Injectables can be prepared in conventional forms, either as liquid solutions, suspensions, or emulsions. Suitable excipients include, for example, water, saline, aqueous dextrose, glycerol, ethanol or the like. In addition, the pharmaceutical compositions may also contain minor amounts of non-toxic substances such as wetting or emulsifying agents, auxiliary pH buffering agents and the like, such as, sodium acetate, sorbitan monolaurate, triethanolamine oleate, etc. The percentage of active compound contained in such parenteral compositions is highly dependent on the specific nature thereof, as well as the activity of the compound and the needs of the subject. However, percentages of active ingredient in solution are in general 0.1 % to 10%, and preferably 0.2-2%. Other modes of administration can also be practiced in accordance with the present invention. For example, intravenous, intramuscular, and subcutaneous delivery are examples of delivery methods that are contemplated by the present invention. For delayed release, the compounds of the invention may be formulated in a composition, such as in microcapsules formed from biocompatible polymers, or in liposomal carrier systems according to methods known in the art. For continuous release of active agent, the compound maybe covalently conjugated to a water soluble polymer, such as a polylactide or biodegradable hydrogel derived from an amphipathic block copolymer, as described in U.S. Patent No. 5,320,840. Collagen-based matrix implants, such as described in U.S. Patent No. 5,024,841, are also useful for sustained delivery of therapeutics. In one embodiment, an oral dose of L-citrulline of <1.7 gram per day; or 250, 500, 750, or 1000 to 1600 mg/day; or 250, 500, 750, or 1000 to 1500 mg/day; is effective in treating vascular disease such as erectile dysfunction, nitrate tolerance, peripheral arterial disease, coronary artery disease, sickle cell disease, migraine headache, and cerebrovascular disease. This dose of L-citrulline prevents nitrate tolerance that is caused by continuous administration of organic nitrates such as nitroglycerin, isosorbide mononitrate, or isosorbide dinitrate. In another embodiment, an oral dose of L-citrulline of <1.7 gram per day; or 250, 500, 750, or 1000 to 1600 mg/day; or 250, 500, 750, or 1000 to 1500 mg/day; is effective in treating male and female sexual dysfunction. L-citrulline is particularly effective when given in combination with ginseng extracts and/or ginkgo biloba extracts. Ginseng extracts are, for example, given in an amount of 5-500 mg per day, preferably 50-250 mg per day, and more preferably 75-150 mg per day. Ginkgo biloba are, for example, given in an amount of 5-200 mg per day, preferably 25-100 mg per day, and more preferably 35-70 mg per day. In another embodiment, an oral dose of L-citrulline of <1.7 gram per day; or 250, 500, 750, or 1000 to 1600 mg/day; or 250, 500, 750, or 1000 to 1500 mg/day; is effective in treating male infertility. L-citrulline is particularly effective when given in combination with L-carnitine. L-carnitine is, for example, given in an amount of 200-2000 mg per day, preferably 400-1600 mg, and more preferably 800-1300 mg per day. hi another embodiment, an oral dose of L-citrulline of <1.7 gram per day; or 250, 500, 750, or 1000 to 1600 mg/day; or 250, 500, 750, or 1000 to 1500 mg/day; is effective in treating female infertility and improving follicular formation and uterine perfusion. L- citrulline is particularly effective when given with chasteberry (extracts of Vitex agnus castus), and/or green tea extracts. Chasteberry is often given in an amount of 25 to 250 mg per day, preferably 50 to 150 mg per day, and more preferably 60 to 100 mg per day. Green tea extracts are often given in an amount of 50-500 mg per day, preferably 100 to 300 mg per day.

The following examples further illustrate the present invention. These examples are intended merely to be illustrative of the present invention and are not to be construed as being limiting.

EXAMPLES Example 1 : Human subjects were enrolled in a crossover pharmacokinetic study where the subjects take orally either L-arginine or L-citrulline in doses of 750 mg twice a day. Serum levels of plasma L-arginine are taken at baseline prior to dosing, and at several time points over the next 24 hours, to generate a pharmacokinetic curve, to determine the bioavailability and ability of L- arginine or L-citrulline to increase plasma L-arginine levels. The data indicate that 750 mg of citrulline given twice a day gives more than 50% greater increased serum L-arginine as compared to the same dose of arginine by weight. The data also indicate that human subjects taking citrulline show substantially better vascular function as measured by ultrasound in comparison with human subjects taking arginine.

Example 2: Women suffering from sexual dysfunction are given the self-administered Female Sexual Function Index (FSFI) to quantify overall satisfaction with sexual function, sexual desire, quality of sexual intercourse, orgasm, lubrication, and clitoral sensation. A composition comprising 750-1500 mg L-citrulline, and optionally 25-100 mg ginkgo biloba extract and/or 50-250 mg ginseng root extract, is given orally twice a day to female subjects for 25-60 days. The FSFI index is measured at baseline, and after the study period. The difference in FSFI index is measured at the end of the study from baseline. The treatment group shows an increased percentage of women who improve by at least one point on the various subparts of the FSFI scale.

Example 3: Men suffering from erectile dysfunction are given a self-administered Sexual Function Questionnaire (SFQ) to quantify overall satisfaction with sexual function, erectile function, sexual desire, quality and frequency of sexual intercourse, and orgasm. A composition comprising 750-1500 mg L-citrulline, and optionally, 25-100 mg ginkgo biloba extract and/or 50-250 mg ginseng root extract, or placebo, is given orally twice a day to male subjects for 25-60 days. The SFQ index is measured at baseline, and at the end of the study. The difference in SFQ index is measured at the end of the day from baseline. The treatment group shows that several subjects improve by at least one point on the various subparts of the SFQ scale.

Example 4: Women suffering from infertility are enrolled in a study, where the endpoint of the study is a positive pregnancy test. None of the patients have taken fertility treatments within one month of initiating the study. A composition comprising 750-1500 mg citrulline and 60-100 mg chasteberry extract, and optionally 100-300 mg green tea extract, is administered orally twice a day to female subjects for 60-120 days. Several patients achieve a positive pregnancy test in the treatment group, demonstrating efficacy of the composition.

The invention, and the manner and process of making and using it, are now described in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains, to make and use the same. It is to be understood that the foregoing describes preferred embodiments of the present invention and that modifications may be made therein without departing from the scope of the present invention as set forth in the claims. To particularly point out and distinctly claim the subject matter regarded as invention, the following claims conclude the specification.

Claims

WHAT IS CLAIMED IS:

1. A method of treating sexual dysfunction, comprising the step of administering to a subject suffering from sexual dysfunction a composition comprising a therapeutically effective amount of L-citrulline, wherein the therapeutically effective amount of citrulline is less than 1.7 g per day.

2. The method according to Claim 1, wherein said composition further comprises ginkgo extracts.

3. The method according to Claim 1, wherein said composition further comprises ginseng extracts.

4. The method according to Claim 1, wherein said composition further comprises ginseng extracts and ginkgo extracts.

5. A method of treating a vascular disease selected from the group consisting of peripheral arterial disease, sickle cell disease, and migraine headache, comprising the step of administering to a subject suffering from peripheral arterial disease, sickle cell disease, or migraine headache a composition comprising a therapeutically effective amount of L- citrulline, wherein the therapeutically effective amount of citrulline is less than 1.7 g per day.

6. A method of treating infertility in a female subject, comprising the step of administering to a female subject suffering from infertility a composition comprising a therapeutically effective amount of L-citrulline and extracts of Vitex agnus castus, wherein the therapeutically effective amount of citrulline is less than 1.7 g per day.

7. A method of treating infertility in a female subject, comprising the step of administering to a female subject suffering from infertility a composition comprising a therapeutically effective amount of L-citrulline and extracts of green tea, wherein the therapeutically effective amount of citrulline is less than 1.7 g per day.

8. The method according to Claim 7, wherein said composition further comprises extracts of Vitex agnus castus.

9. A method of treating infertility in a male subject, comprising the step of administering to a male subject suffering from infertility a composition comprising a therapeutically effective amount of L-citrulline and L-carnitine, wherein the therapeutically effective amount of citrulline is less than 1.7 g per day.

10. The method according to Claim 9, wherein the subject has a condition selected from the group consisting of poor sperm motility, oligospermia, and poor sperm linearity.

11. The method according to any one of Claims 1-10, wherein the therapeutically effective amount of citrulline is between 750 mg and 1.6 g.

12. The method according to any one of Claims 1-10, wherein the therapeutically effective amount of citrulline is between 1.0 g and 1.5 g.

13. The method according to any one of Claims 1-10, wherein said composition is administered orally to said subject.

14. The method according to any one of Claims 1-10, wherein said composition is administered in a form of a capsule, tablet, or liquid.

15. The method according to any one of Claims 1-10, wherein said composition is a pharmaceutical composition.

16. The method according to any one of Claims 1-10, wherein said composition is a nutraceutical composition.