An Investigation of the Metabolism of Amitriptyline Using High Performance Liquid Chromatography

Abstract

A systematic study of the metabolism of the antidepressant amitriptyline was conducted using an inbred strain of rats. Variables affecting rat liver metabolism in vitro that were examined include age of the rat, the substrate concentration, and pH. A liquid-liquid extraction with hexane-butanol and back extraction into phosphoric acid was developed to provide efficient extraction for the wide range of polarity exhibited by amitriptyline and seven metabolites (amitriptyline-N-oxide, cis and trans isomers of 10-hydroxy-amitriptyline, cis and trans isomers of 10-hydroxynortriptyline, nortriptyline, and desmethylnortriptyline). HPLC was performed with 5 μm C-8 reversed phase column and a methanol/sodium phosphate buffer/amine modifier mobile phase.