Quantitation of pentisomide and its metabolite by high-pressure liquid chromatography in human serum.

A rapid, inexpensive, and accurate high-performance liquid chromatographic method for the simultaneous determination of pentisomide and its major mono-N-dealkylated metabolite has been developed. After a simple and inexpensive solvent extraction procedure, the unchanged drug, its metabolite, and the internal standard are separated using a C18 reversed-phase column with a 5-microns particle size. The eluent is monitored with ultraviolet detection at 260 nm. Endogenous substances or a variety of drugs do not interfere with the assay. The mean recoveries of pentisomide and its metabolite are 92.6% and 92.2%, respectively. The limit of detection of the assay is 28 ng/mL for both drugs. Serum levels of pentisomide and its metabolite in patients on oral therapy for supraventricular tachycardia are reported.