Allopurinol does not increase free radical scavenging capacity during reperfusion in coronary artery bypass graft patients

Objectives: Allopurinol protects the heart against ischaemic events during coronary artery bypass grafting (CABG), possibly because of its antioxidant properties. This double-blind study was designed to investigate whether al lopurinol (1 g), given before cardiopulmonary bypass and prior to the openi ng of cross-clamping, has an antioxidant effect in CABG patients by measuri ng plasma total peroxyl radical scavenging capacity. Design: Twenty-seven patients with stabile angina were randomized into allo purinol (n = 14) or placebo (n = 13) groups. Results: During 10 min reperfusion, plasma hypoxanthine and xanthine concen trations increased only in the allopurinol group, whereas uric acid concent rations decreased. Total peroxyl radical scavenging capacity (TRAP) decreas ed from the initial value at all measuring points in both groups. Conclusions: The reducing effect of allopurinol on free radical generation cannot be seen in TRAP values, obviously because the uric acid concentratio n of plasma decreases markedly. The positive clinical effects of allopurino l in CABG patients may arise from its direct oxygen free radical scavenging function.