High-performance liquid chromatographic method for stability and pharmacokinetic studies of nicorandil

Nicorandil is a unique vasodilator that combines the actions of a potassium channel activator and a nitrovasodilator. Little literature is available on its chemical stability and pharmacokinetics in animals. We developed a simple, specific, sensitive, and precise high-performance liquid chromatographic method for the determination of nicorandil in aqueous solution and rat plasma, achieving a detection limit of 0.3 microgram/ml with 180-microliters samples. Nicorandil was found to be relatively stable between pH 2 and 10 at 37 degrees C (half-life = 461-84 h) and it is subjected to specific base catalysis above pH 10. Both chemical degradation and in vivo metabolism produced N-(2-hydroxyethyl)nicotinamide, the denitrated product. Preliminary pharmacokinetic investigations showed that the assay is capable of quantitating nicorandil in rat plasma over a range of 0.3-100 micrograms/ml. These studies also suggested that the pharmacokinetics of nicorandil are dose-dependent.