The characterization of the metabolites of ranolazine in man by liquid chromatography mass spectrometry

Abstract

The metabolism of ranolazine (RS-43285) or (+)N-(2,6-dimethylphenyl)-4[2-hydroxy-3-(2-methoxyphenoxy)-propyl]-1- piperazine acetamide dihydrochloride was investigated in man using plasma samples obtained from four different clinical studies. The metabolite profiles following single and multiple doses of 342 mg instant release (IR) ranolazine, following multiple doses of 1000 mg sustained release (SR) ranolazine and following dosing with both ranolazine (IR) and a potentially co-administered drug, diltiazem, were compared. Metabolism of ranolazine in man was shown by LC/MS analysis to be extensive with up to seven primary routes of metabolism identified. N-dealkylation by hydrolysis at the piperazine ring produced three metabolites whilst O-demethylation and O-dearylation at the methoxyphenoxy moiety produced a further two compounds. Additionally, hydrolysis of the amide group formed one other species. Oxygenation at various points in the molecule produced a further four metabolites. Direct conjugation of ranolazine with glucuronic acid and with an uncharacterized adduct were also identified as a route of elimination. Ten other biotransformation products were formed as a result of multiple metabolic steps. Conjugation was also associated with the desmethyl metabolite (glucuronide and unidentified conjugates) of hydroxylated ranolazine. In a previous publication (Journal of Chromatography, 1995, accepted for publication) semi-quantitative analyses of pooled plasma from the study where ranolazine was dosed at 1000 mg twice daily showed that of the twelve metabolites studied only four accounted for AUC's in excess of 10% of the ranolazine AUC.