Selective Estrogen Receptor Modulators

Abstract

Selective estrogen receptor modulators (SERMs) competitively bind to estrogen receptors to act as agonists or antagonists in certain tissues, distinguishing the various available SERMS. Although tamoxifen, toremifene, and additional new compounds are discussed briefly, raloxifene is the only SERM currently indicated for the prevention and treatment of postmenopausal osteoporosis in women. The effects of raloxifene on vertebral fractures, nonvertebral fractures, and bone mineral density (BMD) have been explored. In the Multiple Outcomes of Raloxifene Evaluation (MORE) trial, vertebral fractures were significantly reduced in the raloxifene treatment group (relative risk of 0.60, 95% confidence interval 0.50–0.70, p<0.01). Raloxifene did not significantly reduce nonvertebral fractures with either 60 or 120 mg/d in the MORE trial. BMD increased by 0.4 to 1.20% at the lumbar spine and the effects have been documented for at least 7 yr in the Continuing Outcomes Relevant to Evista trial. Fracture prevention is greater than expected based on BMD changes. Adverse effects that should be considered with raloxifene include hot flushes and an increased risk for venous thromboembolism. Raloxifene is a viable option for postmenopausal patients with osteoporosis, particularly in patients at increased risk of invasive breast cancer. Although not yet indicated by the US Food and Drug Administration for breast cancer prevention, clinical trail data is encouraging.