Raloxifene, the first of a new class of drugs, termed selective estrogen receptor modulators (SERMs), has estrogen agonist effects on bone and antagonist effects on breast and endometrium. It blocks estrogen in a similar manner to tamoxifen, while also binding and stimulating other tissue receptors to act like estrogen. Raloxifene inhibits trabecular and vertebral bone loss in a manner similar, but not identical, to estrogen - i.e. by blocking the activity of cytokines that stimulate bone resorption.
Raloxifene therapy results in decreased serum total and low-density lipoprotein (LDL) cholesterol without any beneficial effects on serum total high-density lipoprotein (HDL) cholesterol or triglycerides.41,42 The side effects of raloxifene are vaginitis and hot flushes.43 Investigators in the Multiple Outcomes of Raloxifene (MORE) trial of more than 7000 postmenopausal, osteoporotic women over three years showed a decreased breast cancer risk in those already at low risk for the disease.44 The study results were analyzed separately for women presenting with pre-existing fracture. While treatment effectiveness was similar in both groups, the absolute risk of fractures in the group with pre-existing fractures was 4.5 times greater than in the group with osteoporosis but no pre-existing fracture (21% versus 4.5%). Thus, it is important to identify and treat patients at higher risk. Studies of women at higher risk for breast cancer are currently under way.
A summary of overall treatment strategies is given in Table 14.6, and guidelines for dosing of the pharmacologic agents are given in Table 14.7.
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