Although there is some evidence against sexual dysfunction occurring in patients taking 5 mg and 10 mg of finasteride, most studies describe relatively common adverse effects of decreased libido, impotence, and ejaculation disorders... We identified 5 studies that did not support the increased rates of sexual dysfunction in men taking 1 mg finasteride for androgenic alopecia. However, we feel that the evidence describing increased rates of sexual dysfunction is more compelling. We identified 10 studies demonstrating sexual adverse effects, including ED and decreased libido... Three studies identified in this review describe complete reversibility of sexual dysfunction in all patients, but 11 studies describe patients experiencing irreversible adverse effects. These findings were most convincing in a retrospective review of 11,909 patients that identified 167 with persistent ED.
Zakhem, George A. et al. [Journal of the American Academy of Dermatology]