Finasteride blocks the action of an enzyme called 5-alpha-reductase. This enzyme changes testosterone to another hormone that causes the prostate to grow. It will increase testosterone levels in the body, which decreases prostate size. The effect of finasteride will only last as long as the medicine is taken.

Finasterideis used alone or in combination with another medication (doxazosin [Cardura]) to treat benign prostatic hypertrophy (BPH, enlargement of the prostate gland). Finasteride is used to treat symptoms of BPH such as frequent and difficult urination and may reduce the chance of acute urinary retention (sudden inability to urinate). It also may decrease the chance that prostate surgery will be needed. Finasteride is also used to treat male pattern hair loss (gradual thinning of the hair on the scalp, leading to a receding hairline or balding on the top of the head in men.) Finasteride has not been shown to treat thinning hair at the temples and is not used to treat hair loss in women or children. Finasteride is in a class of medications called 5-alpha reductase inhibitors. Finasteride treats BPH by blocking the body's production of a male hormone that causes the prostate to enlarge. Finasteride treats male pattern hair loss by blocking the body's production of a male hormone in the scalp that stops hair growth.

Finasteride comes as a tablet to take by mouth. It is usually taken once a day with or without food. Take finasteride at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take finasteride exactly as directed.

If you are taking finasteride to treat BPH, you should know that finasteride may control your condition, but will not cure it. It may take at least 6 months before your symptoms improve. Continue to take finasteride even if you feel well.

If you are taking finasteride to treat male pattern hair loss, it may take at least 3 months before you see any improvement because hair loss and growth happen slowly over time. However, you should expect to see improvement during the first 12 months of your treatment. If you have taken finasteride for 12 months and have not noticed any improvement, further treatment probably will not help. Talk to your doctor about whether you should continue your treatment.

Finasteride will only slow hair loss while you are taking the medication. Continue to take finasteride even if you have already noticed an improvement. Do not stop taking finasteride without talking to your doctor. You will probably lose any hair that grew back while you were taking finasteride during the first 12 months after you stop taking the medication..