Finasteride is a FDA approved oral medicine for hair loss in men.
Finasteride inhibits the formation of DHT, a hormone that responsible for male pattern hair loss.
Around 90% of men treated with Finasteride were found to have the progress of their hair loss slowed down and 60% had increase in hair growth.
Concerning the side effects, 1-2% of men treated with Finasteride may have deleterious effect of sexual function including impotence and decreased sex drive. Sexual side effects related to Finasteride almost universally resolve after discontinuation of the medication.
Minoxidil is another FDA-approved drug for treatment of hair loss. It is a topical medicine to apply over the scalp. It dilates blood vessel and stimulates growth of hair.
Small number of people treated by Minoxidil may develop scalp irritation after using Minoxidil. Once again the side effects will resolve once the treatment is terminated.