Nicorandil-d4 is intended for use as an internal standard for the quantification of nicorandil by GC- or LC-MS. Nicorandil is an activator of sulfonylurea receptor 2B (SUR2B) linked to ATP-sensitive potassium channel Kir6.2 (EC50 = ~10 µM) and a nitric oxide (NO) donor. It is selective for SUR2B/Kir6.2 over the SUR2A/Kir6.2 channel (EC50 = >500 µM). Nicorandil activates soluble guanylate cyclase in a cell-free assay and relaxes partially depolarized isolated bovine coronary artery strips (EC50 = 4.4 µM). It decreases mean blood pressure, coronary resistance, and heart rate, as well as increases coronary sinus outflow, in dogs when administered intravenously at a dose of 1 mg/kg. Nicorandil increases survival and decreases infarct size in a rabbit model of myocardial ischemia-reperfusion injury induced by left coronary artery occlusion. Formulations containing nicorandil have been used in the treatment of angina pectoris.