Rapid and sensitive LC-MS/MS method for quantification of lamotrigine in human plasma: application to a human pharmacokinetic study.

A highly sensitive, specific and fully validated LC-MS/MS method as per general practices of industry has been developed for estimation of lamotrigine (LAM) with 100 µL of human plasma using flucanozole as an internal standard (IS). The API-4000 LC-MS/MS was operated under the multiple reaction-monitoring mode using electrospray ionization. A simple liquid-liquid extraction process was used to extract LAM and IS from human plasma. The total run time was 2.0 min and the elution of LAM and IS occurred at 1.25 and 1.45 min; this was achieved with a mobile phase consisting of 0.1% formic acid-methanol (20:40:40, v/v) at a flow rate of 0.50 mL/min on a Discovery CN (50 × 4.6 mm, 5 µm) column. The developed method was validated in human plasma with a lower limit of quantitation of 0.1 ng/mL for LAM. A linear response function was established for the range of concentrations 0.1-1500 ng/mL (r > 0.998) for LAM. The intra- and inter-day precision values for LAM met the acceptance as per Food and Drug Administration guidelines. LAM was stable in the set of stability studies, viz. bench-top, autosampler and freeze-thaw cycles. The developed assay method was applied to an oral bioequivalence study in humans.