GEMFIBROZIL ENHANCES PLATELET ACTIVITY IN PATIENTS WITH COMBINED HYPERLIPOPROTEINEMIA

A placebo-controlled crossover study was conducted to evaluate whether lipid-lowering with gemfibrozil (10 to 12 weeks) affects platelet fun ction in vivo at rest and during mental stress in 21 men with combined hyperlipoproteinemia. Gemfibrozil lowered plasma triglycerides and to tal and VLDL cholesterol (P<.001 for all), whereas HDL cholesterol inc reased (P<.001). Gemfibrozil increased platelet counts by 18% (P<.001) and, according to filtragometry measurements, enhanced overall (means of rest and stress values) platelet aggregability in vivo (P=.014); t his effect was more evident during mental stress (P=.027) than at rest (P=.18). Moreover, the urinary excretion of 11-dehydro-thromboxane-B- 2 was 54% higher during treatment with gemfibrozil (P<.001), whereas t he excretion of beta-thromboglobulin in urine was unaltered. Plasma be ta-thromboglobulin tended to be slightly elevated during active treatm ent (P=.15). Mental stress increased heart rate and catecholamine leve ls and elevated all cholesterol fractions (P<.01) and plasma beta-thro mboglobulin (during placebo, P=.02), but platelet aggregability did no t increase significantly. A positive correlation was found between 11- dehydrothromboxane-B-2 excretion and LDL cholesterol levels during pla cebo (r=.62, P=.0057). In conclusion, gemfibrozil has beneficial effec ts on plasma lipoprotein levels but enhances several aspects of platel et activity in vivo and increases platelet counts. These changes might be prothrombotic and thus adverse for the hyperlipidemic patient. Pri mary preventive effects of gemfibrozil might be enhanced if a platelet inhibitor such as aspirin is administered with gemfibrozil.