Pharmacology and therapeutic effects of nicorandil

Nicorandil, a nicotinamide derivative, is an orally efficacious antianginal drug possessing a nitrate moiety in its chemical structure. This drug is an effective and well-tolerated treatment for various types of angina pectoris. Its general efficacy is similar to that of nitrates, with several unique effects on the cardiovascular system. Nicorandil causes sustained dilation of both the arterial resistance and conductive vessels, thus markedly dilating the coronary artery and increasing coronary blood flow. In addition, nicorandil, unlike nitroglycerin or isosorbide dinitrate, possesses little hemodynamic effect on heart rate, blood pressure, or cardiac contractility with clinical doses yielding antianginal effects. The mechanism causing coronary vasodilation has not been completely clarified but appears to be associated partly with increases in c-GMP, as well as the hyperpolarization of the smooth muscle membrane. Nicorandil, in single oral doses of 10-30 mg, has been shown to be effective in chronic stable angina, as assessed objectively by increases in exercise duration and/or the time to onset of ST-segment depression during treadmill exercise. In open studies and controlled efficacy evaluations, nicorandil in daily oral doses of 15-40 mg demonstrated significant effectiveness in the treatment of various types of angina pectoris. Headaches due to vasodilation may occur, and some side effects occurred in 5.1-34% of patients receiving nicorandil, but were generally minor in nature. There was no depressant effect on atrioventricular conduction, which occurs frequently in patients treated with calcium antagonists of the verapamil and diltiazem type. Nicorandil may be effective even in patients with rest and effort angina who do not respond to combination therapy with calcium antagonists and oral nitrates. Thus, nicorandil appears to be a valuable addition to the arsenal of antianginal drugs due to its low incidence of serious side effects.