Clomiphene (Clomid)

Clomiphene citrate (brand name Clomid) is a selective estrogen receptor modulator (SERM). By blocking estrogen's negative feedback on the hypothalamus and pituitary, it causes the body to release more FSH and LH, stimulating one or two follicles to develop and ovulate.

It is typically taken on cycle days 3–7 or 5–9 at doses of 50–150 mg. Common uses include anovulation (especially from PCOS) and unexplained infertility. Side effects include hot flashes, mood changes, cervical mucus thinning, and a ~10% risk of twins. Letrozole has largely replaced clomiphene for PCOS because of better ovulation and live birth rates.