THE EFFECT OF PROBUCOL ON FEMORAL ATHEROSCLEROSIS - THE PROBUCOL QUANTITATIVE REGRESSION SWEDISH TRIAL (PQRST)

The Probucol Quantitative Regression Swedish Trial tested whether treatment of hypercholesterolemic persons with probucol for 3 years affected femoral atherosclerosis. The primary end point was the change in atheroma volume estimated as change in lumen volume of the femoral artery assessed by quantitative arteriography. Three hundred three patients with visible atherosclerosis were randomized to probucol 0.5 g twice daily, or to placebo. All patients were given diet and cholestyramine, 8 to 16 g/day. Twenty-nine patients were excluded because of inadequate primary end point measurements. The mean age of the remaining 274 subjects (158 were men) was 55 years. Seventeen percent had intermittent claudication and 24% bad angina pectoris. After 3 years, the probucol-treated patients had 17% lower serum cholesterol, 12% lower low-density lipoprotein cholesterol, 24% lower total high-density lipoprotein cholesterol, and 34% tower high-density lipoprotein(2) cholesterol levels than control subjects. All lipoprotein differences between the treatment groups remained highly significant during the trial. There was no statistically significant change in lumen volume between the probucol and the control group. Furthermore, there was no difference between the treatment groups with regard to change in arterial edge roughness or amount of aorto-femoral atherosclerosis; neither were there any differences between the treatment groups with regard to change in ST-segment depressions on exercise tests or ankle/arm blood pressure (secondary end points). In the control group, lumen volume increased (p <0.001) and roughness of the femoral artery decreased (p <0.05). It is concluded that the addition of probucol to diet and cholestyramine did not result in any significant regression of atherosclerosis compared with that found in patients treated only with diet and cholestyramine. However, in this control group there was statistically significant evidence of improvement.