SOLID-PHASE EXTRACTION STUDY AND RP-HPLC ANALYSIS OF LAMOTRIGINE IN HUMAN BIOLOGICAL-FLUIDS AND IN ANTIEPILEPTIC TABLET FORMULATIONS

An efficient off-line solid-phase extraction (SPE) of lamotrigine, 3,5 -diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine (LTG), a new antiepilep tic drug, from human serum and urine, prior to high-performance liquid chromatographic analysis, was tested and optimized. High extraction r ecoveries were achieved from C-8 Bond Elut cartridges (200mg/3ml), usi ng acidic acetonitrile for the elution of LTG and the internal standar d, 3,5-diamino-6-(2-methoxyphenyl)-1,2,4-triazine. Isocratic reversed- phase high-performance liquid chromatographic (RP-HPLC) analysis on oc tylsilica, using a Lichrosorb RP-8, 5 mu m, 250 x 4.6 mm i.d. column a nd a mobile phase consisting of 0.05M acetate buffer pH5.6 and acetoni trile (72:28 v/v) proved to be sensitive and rapid. The identification of LTG was performed by UV detection at 306nm. The method detects app roximately 0.9 ng of LTG on-column, using a 20-mu l loop, and linearit y holds from approximately 0.044 to 7.8 mu g/ml in standard solutions. In plasma and urine, the limits of detection are 1.1 and 1.2ng respec tively, while linearity holds from approximately 0.087 to 3.49 mu g/ml . The proposed method was also used for the direct analysis of antiepi leptic tablets.