Spironolactone is a diuretic, a medication which prevents testosterone from binding to receptors on the hair follicles, thus blocking the effect of testosterone and helping to limit abnormal hair growth. It is usually given in dosages of 50 to 200mg each day, and may take up to six months before the maximal effect is seen.
Side effects of spironolactone include low blood pressure or altered potassium levels. Your doctor may want to monitor your potassium levels through periodic blood tests. Spironolactone may be used with oral contraceptives for a greater result.