Generically referred to as finasteride, Propecia is an anti-androgen used for the treatment of male pattern hair loss or the gradual thinning of the hair on the scalp, leading to a receding hairline or balding on the top of the head in men. Propecia treats male pattern hair loss by blocking the body's production of a male hormone in the scalp that stops hair growth. Finasteride is in a class of medications called 5-alpha reductase inhibitors which prevent the conversion of testosterone to dihydrotestosterone (DHT) in the body.

Propecia has not been shown to treat thinning hair at the temples and is not used to treat hair loss in women or children.