Unequal disposition of enantiomers of the organic cation oxyphenonium in the rat isolated perfused liver.

This paper describes the results of pharmacokinetic experiments in the rat isolated perfused liver with enantiomers of oxyphenonium. The study was performed with the [14C]methyl labelled compounds. In this preparation both metabolism and biliary excretion were significantly different for the (+)- and the (-)-isomer. Hepatic uptake rate was similar, but total biliary excretion (including metabolites) of the (-)-isomer was only 55% compared with the excretion of the (+)-isomer. In line with these data, after 2 h only 30% of the dose of the (+)-isomer and over 50% of the dose of the (-)-isomer was still found in the liver, predominantly in the form of metabolites. The metabolic profile was investigated using ion pair TLC. At least two metabolites were detected in bile for both enantiomers. However, unchanged (-)-oxyphenonium persisted for longer in bile, indicating either a more rapid canalicular transport of the (+)-isomer and/or a more rapid metabolism of (+)-oxyphenonium to cholephilic metabolites.