Cimetidine, brand name Tagamet, belongs to a class of histamine blockers used mainly to treat gastrointestinal ulcers. The histamine-blocking action prevents the stomach from producing excess acid, allowing the body to heal the ulcer. Cimetidine also has a fairly powerful anti-androgenic effect and has been shown to block dihydrotestosterone from binding the follicle receptor sites.
Cimetidine has been used to treat excess facial hair growth (hirsutism) in women and has shown promising results in studies of women with androgenic alopecia. High doses are needed to achieve results, so men should not take cimetidine to treat their hair loss due to possible feminizing effects, including adverse sexual side effects.