Propecia (finasteride) is a prescription drug that works for most males willing to grow back some of the hair they have lost. The effects of Propecia are based on its active ingredient finasteride interfering with a hormone called DHT thought to interrupt the normal process of hair growth. The areas affected most include the crown area, the temporal area and the top of the scalp, which has to do with special glands that produce DHT and are concentrated there. This drug is not exactly a cure for the condition, but a treatment that needs to be used all the time to achieve stable results. Once you started taking Propecia you will have to continue the treatment in order to ensure visible results. If you decide to stop the treatment you will most likely lose all of the hair you have re-grown.