Nicorandil suppressed myocardial purine metabolism during exercise in patients with angina pectoris.

To elucidate the effect of Nicorandil on myocardial energy metabolism and myocardial sympathetic activity, we administered Nicorandil orally to eight patients with angina pectoris prior to exercise testing. Arterial and coronary sinus levels of lactate, ammonia, hypoxanthine (HX), adrenaline and noradrenaline were measured during exercise in order to determine the irrespective myocardial extraction ratios (MER). Compared to placebo, Nicorandil increased the time to development of significant ST depression (322 vs 390 s) while decreasing the maximum amplitude of ST depression (0.244 vs 0.216 mV). Heart rate, systolic blood pressure, and the rate pressure product during exercise were not significantly affected. The MER of lactate, measured during exercise, was significantly higher after Nicorandil than placebo (13.6 vs 27.9). Similarly, the MERs of ammonia and HX were significantly higher after Nicorandil (-46.0 vs 7.4% and -47.0 vs 9.9% respectively). Nicorandil, had no apparent effect on myocardial sympathetic activity as the MERs of adrenaline and noradrenaline were essentially unaffected. We conclude that Nicorandil decreased myocardial ischaemia and suppressed myocardial accelerated purine metabolism (a marker of cellular energy metabolism) during exercise in patients with angina pectoris. This effect appears not to be related to myocardial sympathetic activity.