Abstract 3114: Antiplatelet Therapy Use and the Risk of Venous Thromboembolic Events in the Double-Blind Raloxifene Use in The Heart (RUTH) Trial

Abstract

Background: Raloxifene (RLX) use in postmenopausal women (PMW) with osteoporosis increases risk of venous thromboembolic events (VTE) 2-fold, compared to placebo (PL). Platelet activation is involved in the pathophysiology of arterial thromboses more than venous thromboses, but some data suggest that aspirin may reduce VTE risk associated with estrogen use. This analysis examines the effects of concomitant antiplatelet (AP) therapy on VTE risk in RLX-treated women. Methods: In RUTH, 10,101 PMW with coronary heart disease (CHD) or increased risk of CHD were randomized to either PL or RLX 60 mg/d and followed for a median 5.6 yr. Reports of clinical symptoms of VTE were supported by relevant diagnostic data and adjudicated. Concomitant use of AP agents (aspirin, clopidogrel, ticlopidine, dipyridamole) was allowed. Cox proportional hazard models, with use of warfarin, presence of fracture, and/or hospitalization as covariates, were used to estimate hazard ratios (HR) with 95% confidence intervals (CI). Results: Overall, RLX 60 mg/d use was associated with an increased VTE risk [HR 1.44 (95% CI 1.06 –1.95)] from PL. Most women (71%) reported using aspirin, and 14.2% reported using non-aspirin AP agents. VTE risk was similar (HR = 1.04, Table ) for women who used RLX alone versus those who used RLX with AP agents. The increase in VTE risk with RLX compared to PL was similar between women who used any AP prior to VTE and those who did not (interaction P=0.29). Women who used aspirin prior to VTE had a similar increased VTE risk with RLX from PL [HR 1.57(95% CI 1.00 –2.47)], compared to women who did not use aspirin [HR 1.34 (95% CI 0.89 –2.01)] (interaction P=0.62). Conclusion: In RUTH, PMW with CHD or at high risk of CHD treated with RLX had an increased risk of VTE compared to PL. Concomitant use of aspirin or non-aspirin AP agents with RLX therapy did not lower VTE risk from RLX alone.