Determination of lamotrigine in human plasma by high-performance liquid chromatography

The method involves precipitation of plasma proteins with acetonitrile and analysis of the supernatant by high-performance liquid chromatography using a 5 mu m Zorbax C8 column. Quantitation was performed by measurement of the UV absorbance at a wavelength of 306 nm. The method was linear in the range of 1-20 mu g/ml, with a mean coefficient of determination (r(2) = 0.998). The limit of detection was 0.6 mu g/ml and the lower limit of quantitation was 1 mu g/ml using 200 mu l of plasma. Within- and between-day accuracy and precision were below 6% at all analysed concentrations except at the limit of quantitation. No interfering peaks were found by commonly monitored antiepileptic drugs. Recovery was found to be greater than or equal to 99%. Satisfactory performance was obtained in the evaluation of epileptic patient samples, whose results of plasma concentration measurements are briefly discussed. We conclude that this is a reliable method for the routine monitoring of lamotrigine concentration in plasma in the clinical setting. (C) 1999 Elsevier Science B.V. All rights reserved.