Finasteride is a drug used in the treatment of benign prostatic hyperplasia (BPH) and androgenic alopecia. It belongs to a class of drugs known as 5-alpha reductase inhibitors, meaning it that blocks the conversion of testosterone to dihydrotestosterone. This reduction in DHT renders the prostate gland smaller while, at the same time, stimulating the follicular growth of hair in those who experience male pattern baldness.Finasteride (Proscar) is a steroid reductase inhibitor which works by reducing the amount of hormone dihydrotestosterone in the body, making the prostate gland smaller. Reducing the size of the prostate gland helps treat urinary problems. Finasteride is mainly used to treat urinary problems caused by conditions such as an enlarged prostate gland or benign prostatic hyperplasia. This medication is also used together with other medications to reduce the amount of dihydrotestosterone in the body. However, Finasteride may also be used for other purposes as determined by the doctor. Do not use Finasteride if you are allergic to any ingredient in it or if you are pregnant. Consult the doctor if this pertains to you before taking Finasteride.