Influence of smoking on the antiosteoporotic efficacy of raloxifene.

Abstract

The efficacy of estrogen therapy may be modified in women who smoke because of increased catabolism of estrogen and the interaction of tobacco products with the estradiol receptor. We examined whether the efficacy of raloxifene differed in smoking vs. nonsmoking women. We compared change in bone mineral density and biochemical markers of bone turnover, and incidence of new vertebral fracture in postmenopausal women of the Multiple Outcomes on Raloxifene Efficacy trial, who were randomized to either raloxifene (60 or 120 mg/d) or placebo. In the 17% of women who were current smokers, we found, compared with nonsmokers, lowered baseline trochanter bone mineral density (0.540 vs. 0.557 g/cm(2); P < 0.001) and serum osteocalcin (24.8 vs. 26.6 ng/liter; P < 0.001). Baseline urinary type I collagen breakdown products was increased among smokers (291.8 vs. 276.9 micromol/liter; P = 0.04). Body mass index was also lower in smokers (24.3 vs. 25.4; P < 0.001). After 6 months of treatment, there was no significant difference in reduction of bone turnover between smokers and nonsmokers. After 4 yr of treatment, the smoking-treatment interaction was not significant between smokers and nonsmokers for the percent increase in femoral neck bone mineral density (P = 0.25), trochanter bone mineral density (P = 0.24), and spine bone mineral density (P = 0.37). The smoking-treatment interaction for reduction in vertebral fracture risk was not significant either [odds ratio for fracture, 0.67 (0.45-0.98) for smokers and 0.56 (0.47-0.68) for nonsmokers; P = 0.44]. These results were not modified after stratification by tertiles of body mass index or when comparing heavy smokers vs. light smokers. We conclude that smoking does not influence the antiosteoporotic effect of raloxifene. This may represent an advantage over estrogen replacement therapy.