What are the side effects of Propecia (Finasteride) and how often do they occur?
Clinical studies showed that side effects were uncommon and did not affect most men. A small number of men had sexual side effects, with each occurring in less than 2% of men. These included less desire for sex, difficulty in achieving an erection, and a decrease in the amount of semen. These side effects went away in men who stopped taking Propecia (Finasteride) because of them. In addition, these side effects decreased to 0.3% or less by the fifth year of treatment.