SELECTIVE ESTROGEN RECEPTOR MODULATOR - Also referred to as selective estrogen receptor modulators (SERM), this relatively new class of drugs is used in the treatment of osteoporosis (and in one case breast cancer). The SERMs exert their effect by binding to estrogen receptors on cells. Physiologically, this leads to a reduction in the resorption of bone and a decrease in overall bone turnover. Examples include the drugs raloxifene and tamoxifen.