Propecia has side effects but they are very limited and often harmless. Propecia has been used by over one million men since its FDA approval 1998. The FDA approval means that Propecia was carefully clinically tested and the test results were well documented.
Propecia (Finasteride) is beside Rogaine (Minoxidil) the only FDA approved drug against hair loss. It works by blocking a major part of the DHT hormone production. DHT is one of the reasons why men loose hair because it makes your hair follicles to shrink and therefore produce thinner hair or no hair at all anymore. Propecia reduces DHT levels so that the hair folicles can recover and produce more hair again.
Propecia side effects happen in less than 2% of men and go away when you stop using the drug. Although very uncommon they can be disturbing because they are of sexual nature. The side effects can be less desire and problems achieving an erection. There might also be a decrease in semen production. The side effects go away when you stop taking Propecia. These side effects also decreased to 0.3% of men or less by the fifth year of treatment.
Propecia can also affect a blood test called PSA (prostate-specific antigen) for the screening of prostate cancer. If you have a such a test done then inform your doctor that you are taking Propecia.
Other side effects are allergic reactions like itching, rash, hives, swelling of the lips and face, breast tenderness and enlargement and testicular pain. If you notice some of these side effects then consult with your doctor.
There are no long-term side effects of Propecia known other than the ones mentioned above. The Propecia alternative Rogaine with the active component Minoxidil also blocks DHT but since it is applied to the head and not taken orally like Propecia the only side effects are a possible itching of the scalp.
Propecia works best for the vertex (top of the head) area. As for the vertex area clinical studies have shown that 2 out of 3 men could stop hair loss and re-grow hair. Propecia is also effective for the anterior mid-scalp (middle front of the head) area. It is not very effective in other areas of the head. It is not for women.