name Propecia®, Finasteride belongs to a class of drugs known as 5-alpha-reductase inhibitors. Consistency is key. If you miss a day, it’s all good, just skip your missed dose and get back on your game the next day. Just don’t take two doses to make up for it. Finasteride treats hair loss in men by blocking DHT (dihydrotestosterone). DHT is an androgen hormone derived from testosterone thought to shrink hair follicles and cause many guys to experience hair loss.