Finasteride is an anti-androgen agent that is used to treat benign prostatic hyperplasia (prostate enlargement) and male pattern baldness.

Finasteride works by inhibiting the type II 5-alpha reductase enzyme, which converts testosterone into its more potent form, dihydrotestosterone (DHT). DHT stimulates development of the penis, testes and scrotum as well as other male sexual characteristics such as body hair and pubic hair. DHT also promotes growth of the prostate. Finasteride can therefore help reduce the size of the prostate in benign prostatic hyperplsia by blocking the conversion of testosterone to DHT and lowering the blood and tissue levels of this hormone.

In 1992, finasteride (5 mg per day) was approved by the U.S. Food and Drug Administration (FDA) as a treatment for benign prostatic hyperplasia. The agent was marketed by Merck under the name Proscar. In 1997, finasteride (1 mg) per day was also approved by the FDA as a treatment for male pattern baldness and this time the agent was marketed by Merck as Propecia.

Some of the brand names which finasteride is sold under include (in alphabetical order) Appecia (from Ajanta Pharma), Finalo (from Intas Pharmaceuticals), Finara (from Ranbaxy), Finast (from Dr. Reddy's), Finasterid Alternova, Finasterid IVAX, Finax (from Dr. Reddy's), Fincar (from Cipla), Finpecia (from Cipla), Finpros (from Zentiva), Hyplafin (from Actavis), Penester (from Zentiva), Prezepa (from Teva), Propecia (from Merck), Proscar (from Merck), Prosteride (from Aleppo Pharmaceutical) and Tectum (from Hemofarm).