Studies on Drug Metabolism by Use of Isotopes. XVII. Mass Spectrometric Quantification of Urinary Metabolites of Deuterated l-Ephedrine in Man

Abstract

In order to develop a practical technique useful for metabolic studies in man by the use of drugs labeled with a stable isotope, l-ephedrine-d₅ was administered to man and the urinary metabolites were quantitatively determined by mass spectrometry. In this method, unlabeled compounds were used as carriers and internal standards for deuterated metabolites of interest. It was thereby found that 75.1% of the administered l-ephedrine was excreted unchanged, 3.6% as norephedrine, and 3.5% as hippuric acid.