Finasteride, sold under the brand name Propecia, prevents the conversion of testosterone to DHT, or dihydrotestosterone, to prevent hair loss, states WebMD. As of 2015, it is the only DHT inhibitor approved by the U.S. Food and Drug Administration for the treatment of male pattern baldness, according to Bosley.
Taking 1 milligram of finasteride per day effectively lowers DHT in men by as much as 60 percent, reports the American Hair Loss Association. During clinical trials, the progression of hair loss stopped in 86 percent of the trial subjects taking finasteride, and 65 percent of the trial subjects exhibited substantial hair growth.
Women and children should not use finasteride. Men must continue taking finasteride to maintain hair growth benefits, notes WebMD.