Liquid chromatography tandem mass spectrometry method for the estimation of lamotrigine in human plasma: Application to a pharmacokinetic study.

A reliable, selective and sensitive liquid chromatography tandem mass spectrometry method was developed and validated for the quantification of lamotrigine in human plasma using lamotrigine-13C3, d3 as an internal standard. Analyte and internal standard were extracted from human plasma by solid-phase extraction and detected in positive ion mode by tandem mass spectrometry with electrospray ionization (ESI) interface. Chromatographic separation was performed on a Chromolith® SpeedROD; RP-18e column (50−4.6mm i.d.) using acetonitrile: 5±0.1mM ammonium formate solution (90:10, v/v) as the mobile phase at a flow rate of 0.500mL/min. The calibration curves were linear over the range of 5.02–1226.47ng/mL with the lower limit of quantitation validated at 5.02ng/mL. The analytes were found stable in human plasma through three freeze (−20°C)-thaw (ice-cold water bath) cycles and under storage on bench-top in ice-cold water bath for at least 6.8h, and also in the mobile phase at 10°C for at least 57h. The method has shown good reproducibility, as the intra- and inter-day precisions were within 3.0%, while the accuracies were within ±6.0% of nominal values. The validated LC–MS/MS method was applied for the evaluation of pharmacokinetic and bioequivalence parameters of lamotrigine after an oral administration of 50mg lamotrigine tablet to thirty-two healthy adult male volunteers.