Use of high-performance liquid chromatography-mass spectrometry for the study of the metabolism of ranitidine in man.

High-performance liquid chromatography has been used for the qualitative analysis of metabolites and the quantitative analysis of ranitidine in the urine from subjects given oral and intravenous doses of ranitidine. Ranitidine, ranitidine-N-oxide, ranitidine-S-oxide and desmethylranitidine were identified in extracts of the urine obtained by the XAD-methanol procedure. A selected-ion monitoring technique, using [2H3]ranitidine as the internal standard, was used to determine ranitidine. A normal-phase system consisting of methanol-propan-2-ol-5 M ammonium acetate (50:50:1) was used, and because of this the volume of urine which could be injected on-column without deterioration of the chromatography was limited to 10 microliters. This limited the sensitivity of the method to 1.0 microgram of ranitidine per millilitre of urine.