Find out how finasteride treats benign prostate enlargement and hair loss in men, and how to take it. NHS medicines information on finasteride – what it's used for, side effects, dosage and who can take it. Finasteride (Propecia, Proscar) is a medication used to treat benign prostatic hyperplasia (BPH) and male-pattern hair loss. It’s more likely to cause side effects at the higher dosage (5 mg) used to treat BPH. Common finasteride side effects include erectile dysfunction and decreased sex drive. Finasteride works by reducing the amount of DHT available by blocking an enzyme called 5α-reductase, which converts testosterone into DHT. Lower levels of DHT help improve hair growth in male pattern hair loss and reduce symptoms of BPH. Finasteride is commonly used to treat BPH, which is non-cancerous enlargement of the prostate. In some people, BPH can occur at the same time as prostate cancer. For the majority of users, finasteride is safe and effective, but a vocal minority say the drug can cause serious, long-term side effects. Taking finasteride leads to a reduction in scalp and serum DHT levels; by lowering scalp levels of DHT, finasteride can maintain or increase the amount of terminal hairs in the anagen phase by inhibiting and sometimes reversing miniaturization of the hair follicle. I've been on Finasteride for 7 years, and I'm 29, no side effects I've noticed. My hair looks better today than when I started. I used to take 1.25mg a day, but now I only take 1.25mg 4 times a week. Finasteride is used to treat men who have symptoms of benign prostatic hyperplasia (BPH) and male pattern hair loss, also called androgenetic alopecia. BPH is caused by an enlarged prostate. 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 oral tablet is a generic drug used to treat benign prostatic hyperplasia and male pattern hair loss. Learn about side effects, dosage, uses, and more.