High-performance liquid chromatographic analysis using a highly sensitive fluorogenic reagent, 2-anthroyl chloride, and stereoselective determination of the enantiomers of mexiletine in human serum.

Abstract

A stereoselective and highly sensitive HPLC assay was developed for mexiletine enantiomers using a new fluorogenic derivatization reagent, 2-anthroyl chloride. The reagent was synthesized and utilized for the fluorescent detection (excitation at 270 nm, emission at 400 nm) of mexiletine enantiomers as their N-anthroyl derivatives on a Pirkle phenylglycine ionic HPLC column. The assay had a lower limit of quantitation at 2.5 ng/ml with a limit of detection measured at 0.5 ng/ml for each enantiomer in serum with a signal-to-noise ratio of 5:1. In a preliminary pharmacokinetic study, 200 mg of racemic mexiletine hydrochloride were administered orally to two healthy volunteers. Serum samples were collected at timed intervals over 48 h. The terminal elimination half-lives determined for total R(-)- and S(+)-mexiletine were 10.9 and 11.5 h, respectively. The serum free fractions for R(-)- and S(+)-mexiletine were found to be 0.56 and 0.53, respectively.