BACKGROUND AND PURPOSE

Raloxifene, a selective estrogen receptor modulator, reduces risk of invasive breast cancer and osteoporosis, but the effect on risk for stroke and venous thromboembolism in different patient subgroups is not established. The purpose of this analysis was to evaluate the effect of raloxifene on the incidence of all strokes, stroke deaths, and venous thromboembolic events according to participant subgroups.

METHODS

This was a secondary end point analysis of an international, randomized, placebo-controlled clinical trial of 10 101 postmenopausal women with or at increased risk of coronary heart disease followed a median of 5.6 years. Strokes, venous thromboembolic events, and deaths were adjudicated by expert centralized committees. Strokes were categorized as ischemic, hemorrhagic, or undetermined and venous thromboembolic events were subclassified.

RESULTS

The incidences of all strokes did not differ between raloxifene (incidence rate per 100 woman-years=0.95) and placebo (incidence rate=0.86) treatment groups (P=0.30). In women assigned raloxifene versus placebo, there was a higher incidence of fatal strokes (incidence rates=0.22 and 0.15, respectively, P=0.0499) and venous thromboembolic events (incidence rates=0.39 and 0.27, respectively, P=0.02). No significant subgroup interactions were found except that there was a higher incidence of stroke associated with raloxifene use among current smokers.

CONCLUSIONS

In postmenopausal women at increased risk for coronary events, the incidences of venous thromboembolism and fatal stroke but not all strokes were higher in those assigned raloxifene versus placebo. Raloxifene's effect did not differ across subgroups, except that the risk of stroke differed by smoking status. Treatment decisions about raloxifene should be based on a balance of projected absolute risks and benefits.

The effects of single doses of intravenous (IV) ciprofloxacin and rifampin and of multiple doses of rifampin on glyburide exposure and blood glucose levels were investigated in nine healthy volunteers. A single IV dose of rifampin significantly increased the area under the concentration-time curve (AUC) of glyburide and its metabolite. Blood glucose levels were significantly lower than those observed after dosing with glyburide alone. Multiple doses of rifampin induced an increase in liver enzyme levels, leading to a marked decrease in glyburide exposure and blood glucose levels. When IV rifampin was administered after multiple doses of rifampin, the inhibition of hepatic uptake transporters masked the induction effect; however, the relative changes in AUC for glyburide and its hydroxyl metabolite were similar to those seen under noninduced conditions. The studies reported here demonstrate how measurements of the levels of both the parent drug and its primary metabolite are useful in unmasking simultaneous drug-drug induction and inhibition effects and in characterizing enzymatic vs. transporter mechanisms.