Finasteride is a medication used to treat male pattern baldness, and is a 5-alpha reductase inhibitor, which means it inhibits the conversion of testosterone to dihydrotestosterone(DHT). Finasteride has been shown to be an effective treatment for male pattern baldness in 9 out of 10 men. It is not an effective treatment for female pattern baldness.
Results can take up to 12 months to be seen, but some men will see results as early as 3 months. 90% success rate is based on a minimum 12-month treatment length. Cessation of the treatment will lead to hair loss resuming within 12 months.