Hemodynamic Actions of Nicorandil, a New Antianginal Agent, in the Conscious Dog

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Abstract
We studied the hemodynamic effects of nicorandil (SG-75) and nitroglycerin in conscious dogs before and after β-adrenergic receptor blockade. Nicorandil (25–300 μg/kg/min) and nitroglycerin (5–60 (μg/kg/min) produced increases in heart rate and decreases in aortic and left ventricular pressures. In the doses studied, nicorandil caused greater decreases in aortic and left ventricular systolic pressure than nitroglycerin; however, nitroglycerin reduced left ventricular end-diastolic pressure to a greater degree. Nicorandil but not nitroglycerin produced an increase in cardiac output secondary to an increase in heart rate. Global contractility (peak positive dP|dt) was increased in a dose-related manner during nicorandil infusion before β-blockade. In spite of marked hypotensive responses to higher doses, mean coronary blood flow and coronary conductance were increased by nicorandil. In contrast, both parameters were reduced during nitroglycerin infusion. The effects of nicorandil on coronary blood flow were unaltered by β-adrenergic blockade, suggesting that metabolic autoregulation is not an important mediator of the response. Nicorandil (75–300 μg/kg/min) produced a dose-related increase in trans-mural myocardial blood flow with the greatest increases in perfusion occurring in the subepicardium and midmyocardium. The results of the present study demonstrate that despite structural similarities, nicorandil and nitroglycerin have varying hemodynamic spectra.