Influence of nicorandil, an antianginal agent, on the therapeutic and toxic cardiovascular actions of ouabain in the anaesthetized dog.

The effects of nicorandil were investigated on ouabain-induced cardiovascular actions in pentobarbitone-anaesthetized dogs. Nicorandil (500 micrograms/kg per h) and ouabain (100 micrograms/kg per h), alone and in combination, were infused intravenously to three groups of dogs. Nicorandil gradually decreased systemic blood pressure, pressure-rate product, left ventricular systolic pressure, and coronary vascular resistance, but did not significantly affect heart rate, left ventricular dP/dt max, coronary blood flow, plasma electrolyte concentrations and ECG patterns. The lethal dose of ouabain was 122 micrograms/kg (s.e.m. = 3, n = 6) and the dose required to elicit ventricular premature beats was 63 micrograms/kg (s.e.m. = 3, n = 6). When nicorandil and ouabain were simultaneously infused intravenously, nicorandil did not affect either the lethal dose of ouabain or the dose required to produce ventricular premature beats, but it significantly inhibited the marked increases in coronary vascular resistance and systemic blood pressure induced by ouabain alone. Even in combination with nicorandil, ouabain maintained its own positive inotropic effect. The results indicate that the combination of ouabain with nicorandil may be beneficial in some conditions of angina pectoris.