Pravastatin potentiates the anticoagulant effects of low molecular weight heparin.

INTRODUCTION: Statins have been shown in randomized trials to reduce coronary events independent of baseline LDL-C level. In the case of pravastatin sodium (PS), there is conflicting evidence as to what is the actual mechanism of its non-lipid lowering beneficial effects. Because pravastatin has been found to prolong the clotting time in vitro, we conducted a study to determine if pravastatin plus low molecular weight heparin (LMWH) would result in a synergistic effect on the in vitro clotting time, thus supporting the hypothesis that pravastatin exerts antithrombotic effects through reduction of fibrin formation.

MATERIALS AND METHODS: Aliquots of PS were combined with dalteparin, a LMWH, in 500 microl of human whole blood. The clotting time in seconds was analyzed on a Sonoclot Coagulation Analyzer, a miniviscometer that is sensitive to early fibrin generation.

RESULTS: PS and LMWH, each resulted in a significant prolongation of the clotting time compared with control. The combination of PS and LMWH resulted in a significantly prolonged clotting time compared with either given alone. All values were significantly different from each other (p<0.05). Our results showed that the combination of PS and a LMWH prolongs the clotting time to a significantly greater degree when compared to either administered alone.

CONCLUSIONS: The synergistic effect of PS and LMWH on prolongation of the clotting time suggests that PS exerts its effect by inhibition of the coagulation cascade and fibrin formation.