Pharmacotherapeutic group: Other vasodilators used in cardiac diseases, ATC code: C01DX16
Mechanism of action
Nicorandil, a nicotinamide ester, is a vasodilator agent with a dual mechanism of action, which leads to relaxation of smooth tonic vascular muscles in both venous and arterial part of vessels.
It possesses a potassium channel opening effect. This activation of potassium channels induces vascular cell membrane hyperpolarisation with an arterial muscle relaxant effect, thereby leading to arterial dilation and afterload reduction. In addition, the activation of the potassium channel leads to cardioprotective effects mimicking ischemic preconditioning.
Due to its nitrate moiety, nicorandil also relaxes vascular smooth muscle, particularly in the venous system via an increase in intracellular cyclic guanosine monophosphate (cGMP). This results in an increased pooling in capacitance vessels with a decrease in preload.
Pharmacodynamic effects
Nicorandil has been shown to exert a direct effect on coronary arteries, both on normal and stenotic segments, without leading to a steal phenomenon. Furthermore, the reduction of end-diastolic pressure and wall tension decreases the extravascular component of vascular resistance. Ultimately, this results in an improved oxygen balance in the myocardium and improved blood flow in the post-stenotic areas of the myocardium.
Furthermore, nicorandil has demonstrated a spasmolytic activity in both in vitro and in vivo studies and reverses coronary spasm induced by methacholine or noradrenalin.
Nicorandil has no direct effect on myocardial contractility.
Clinical efficacy and safety
The IONA study was a randomised, double blind, placebo controlled study carried out in 5126 patients more than 45 years old with chronic stable angina, treated with standard anti-anginal therapies and at high risk of cardiovascular events defined by either: 1) previous myocardial infarction, or 2) coronary artery bypass grafting , or 3) coronary artery disease confirmed by angiography, or a positive exercise test in the previous two years, together with one of the following: left ventricular hypertrophy on the ECG, left ventricular ejection fraction ≤ 45%, or an end diastolic dimension of > 55 mm, age ≥ 65, diabetes, hypertension, peripheral vascular disease, or cerebrovascular disease. Patients were excluded from the study if they were receiving a sulphonylurea as it was felt these patients may not benefit; (sulphonylurea agents have the potential to close potassium channels and may thus antagonise some of the effects of nicorandil). Study follow up for endpoint analysis was between 12 and 36 months with a mean of 1.6 years.
The composite primary endpoint [coronary heart disease (CHD) death, non-fatal myocardial infarction, or unplanned hospital admission for cardiac chest pain], occurred in 337 patients (13.1%) treated with nicorandil 20 mg twice daily compared with 389 patients (15.5%) receiving placebo [hazard ratio 0.83; 95% confidence interval (CI) 0.72 to 0.97; p=0.014].