High-pressure liquid chromatographic analysis of drugs in biological fluids. III. Analysis of disopyramide and its mono-N-dealkylated metabolite in plasma and urine.

A high-pressure liquid chromatographic analysis for disopyramide (I) and its mono-N-dealkylated metabolite (II) in plasma and urine is described. The analysis, in which I and II together with an internal standard are chromatographed as ion pairs with heptanesulphonic acid, employs a simple and rapid method of sample preparation. The method is more sensitive, reproducible, and rapid than previously reported gas chromatographic methods.