[Metabolism and distribution of bupivacaine-experiments in rats I. Methods and metabolism (author's transl)].

A method is described enabling blood concentrations and urinary and biliary excretion of bupivacaine to be estimated in unanaesthetized rats. After enteral application of bupivacaine, the urine volumes of 40 rats are collected, cleared off and analysed by gas chromatography. 5 fractions are obtained, of which the structures are identified by mass spectrometry and nuclear magnetic resonance. The following five metabolites could be identified: (1) Desbutyl-bupivacaine, (2) 3'-Hydroxy-bupivacaine, (3) N-Butylpipecolyl-2-amide, (4, 5) mono-hydroxylated isomeres on the piperidine ring.