The potential side effects of taking finasteride include impotence, loss of interest in sex trouble having an orgasm, erectile dysfunction, abnormal ejaculation, swelling in your hands or feet, increased tenderness and swelling in your breasts, dizziness, weakness, headache, runny nose, skin rash, depression, and sudden fatigue. In more extreme cases, you could experience lumps or pain in your breasts, nipple discharge, or swelling of the lips, tongue, throat, or face.