The U.S. Food and Drug Administration (FDA) recently approved two new formulations of drugs for the treatment of male androgenetic alopecia: finasteride (1 mg) for oral treatment of male pattern baldness and minoxidil (5 percent), a topical solution for over-the-counter use. A lower strength of topical minoxidil (2 percent) is currently marketed for use in both men and women. Consultants for The Medical Letter on Drugs and Therapeutics reviewed the data on the new formulations.

Finasteride is a specific inhibitor of type II 5α-reductase, preventing the conversion of testosterone to a more potent metabolite, dihydrotestosterone. It is known that male pseudohermaphrodites with genetic deficiency of 5α-reductase do not lose their hair. After a 1-mg dose of finasteride, serum concentrations of dihydrotestosterone decrease by 65 percent within 24 hours. Finasteride is well absorbed and has a half-life of five to six hours. The 5-mg tablets have been reported to cause erectile dysfunction, gynecomastia, severe myopathy and loss of libido in older men. Adverse events are reduced with the 1-mg tablets.

Because of teratogenic effects in animals, women of reproductive age are warned not to handle crushed or broken tablets. To date, no clinical studies of finasteride for treatment of hair loss have been published, although the results of three double-blind trials have been presented as abstracts. In two studies, 1,553 men with male pattern baldness took 1 mg of finasteride or placebo for one year. After one year, men taking the active drug had an average of 107 more hairs (a 12 percent increase) in a one-inch diameter circle on the scalp than did those who took placebo. Hair counts were maintained up to 24 months in the men who continued active drug therapy. In the other study of 326 men, those who took finasteride had significantly higher hair counts in the frontal area. However, 30 percent of the men taking placebo said they believed their appearance had improved.

Although its mechanism is not completely understood, minoxidil appears to have a direct effect on hair follicles, which increase in size with treatment. Serum concentrations are much lower after topical application than with use of oral minoxidil. Four unpublished studies presented to the FDA compared preparations of 2 percent and 5 percent minoxidil with placebo. The studies in women found no difference in net hair gain between the two active drugs. In men, new hairs increased by five per cm² in the placebo group, 30 per cm² with 2 percent minoxidil and 39 per cm² with 5 percent minoxidil. When the drug therapy was stopped, the newly regrown hairs were shed. In one double-blind study, topical use of 2 percent minoxidil caused significant increases in left-ventricular end-diastolic volume, cardiac output and left ventricular mass. No studies on the safety of 5 percent minoxidil have been published. Local reactions such as erythema have been reported. Oral minoxidil is associated with hypertrichosis of the fetus and multiple congenital anomalies.

A one-month supply of finasteride in 1-mg tablets costs the pharmacist $46.88. The 5-mg tablets cost $63.23. A one-month supply (60 mL) of 2 percent minoxidil costs the pharmacist $22.56. Generic formulations of the same drug cost an average of $10.82. Five percent minoxidil costs $28.32 for 60 mL.

Medical Letter consultants conclude that both 5 percent minoxidil topical solution and 1 mg oral finasteride can produce a modest increase in hair in young men with mild to moderate hair loss, but both medications must be continued indefinitely to maintain the effect. The long-term safety of either formulation has not been determined. The slight difference in new hair growth between the old 2 percent minoxidil solution and the new 5 percent minoxidil solution does not justify the higher cost and the increased risk of adverse events.