How does finasteride treat enlarged prostate?

Finasteride is the main ingredient in Proscar. This drug is used to treat symptoms of benign prostatic hyperplasia (BPH) in males with an enlarged prostate. Proscar can also be used to reduce the risk of a sudden inability to pass urine. It can also reduce the need for surgery related to BPH in men with an enlarged prostate. BPH is an enlargement of the prostate gland. An enlarged prostate can slowly restrict the flow of urine. This can lead to difficulty voiding, urinary tract infections, and a sudden inability to pass urine. Proscar lowers levels of a hormone called DHT (dihydrotestosterone), which is a cause of prostate growth. Lowering DHT helps shrink the prostate gland in most men.