Use as a treatment for hair loss
In a 5-year study of men with mild to moderate hair loss, 48% of those treated with Propecia (finasteride 1 mg) experienced some regrowth of hair, and a further 42% had no further loss. Average hair count in the treatment group remained above baseline, and showed an increasing difference from hair count in the placebo group, for all five years of the study.[11]
Propecia is effective only for as long as it is taken; the hair gained or maintained is lost within 6–12 months of ceasing therapy.[12] In clinical studies, Propecia, like minoxidil, was shown to work on both the crown area and the hairline,[13] but is most successful in the crown area.
Some users, in an effort to save money, buy Proscar instead of Propecia, and split the Proscar pills to approximate the Propecia dosage. Doing so is generally considered unadvisable if women of pregnancy age are in the household; this is because finasteride, even in small concentrations, can cause birth defects in a developing male fetus. The birth defects involve the development of male genitalia (no such effects have been noted in developing female fetuses). On most product inserts, it will be mentioned that the dust or crumbs from broken Proscar tablets should be kept away from pregnant women.
Propecia has been shown to be ineffective for treating hair loss in women.[citation needed] However, Propecia's supporters respond that the study was on post-menopausal women whose hair loss was more likely related to the loss of estrogen versus a sensitivity to testosterone. Many doctors prescribe it for women, but not without either careful birth control measures or assurance that the woman cannot become pregnant.