Primed in U.S.A. DETERMINATION OF OPTICALLY ACTIVE THIOPENTAL, THIAMYLAL, AND THEIR METABOLITES IN HUMAN URINE

Methods involving solvent extraction and gas-liquid chromatography have been developed for quantitative determination of certain thiobarbiturates and their major metabolites in urine. The structures of the metabolites identified were confirmed by the use of gas chroma-tography/mass spectrometry and 13C-nuclear magnetic resonance spectroscopy. The pres-ent analytic methods were applied to the quantitative determination of (R)-(+)- and (S)-(-)-thiopental as well as (R)-(+)- and (S)-(-)-thiamylal and their major metabolites excreted in human urine. Minor metabolites were isolated and identified. Thiopental and thiamylal are widely used anes-thetic barbiturates which are rapidly redistri-buted into body tissues and fat depots but metab-olized at relatively slow rates in vivo. Some stud-ies of the biotransformation of thiopental in man are available (1-5) but almost none of thiamylal (4)