When applied topically, the amount of minoxidil absorbed through the skin into the bloodstream is usually too small to cause internal side effects.
Widely available in generic versions and under the brand name Rogaine, minoxidil seems to be more effective for women suffering from diffuse androgenetic alopecia than it is for men. Product labeling recommends that women only use the 2% concentration of minoxidil, not 5%, because the FDA has not approved use of the higher concentration in women.
Many dermatologists do prescribe 5% for women with androgenetic alopecia if used under their supervision. Small clinical trials have shown that the 5% minoxidil solution is significantly more effective in both retaining and regrowing hair in women with androgenetic alopecia than the 2% solution.
Results from clinical studies of mostly white women ages 18 to 45 years with mild to moderate degrees of hair loss report that after using minoxidil for eight months, 19% of users had moderate regrowth and 40% had minimal regrowth. Of those using a liquid without active minoxidil (a placebo) during the same time period, 7% reported moderate hair regrowth while 33% had minimal regrowth.