Determination of Lamotrigine and Felbamate in Pediatric Plasma Samples by Reverse Phase High-performance Liquid Chromatography

A simple, sensitive, selective, fast and validated isocratic reversed-phase HPLC method for simultaneous determination of the new generation antiepileptic drugs, lamotrigine (CAS 84057-84-1) and felbamate (CAS 25451-15-4) in human plasma using spectrophotometric detection is presented in this paper. Lamotrigine, felbamate and the internal standard nevirapine (CAS 129618-40-2) were extracted from plasma (100µL) using liquid-liquid extraction under alkaline conditions into an organic solvent. Liquid chromatographic analysis was carried out on a Grace Vydac 5µm RP, 250mm ◊4.6mm I.D. column, using a mixture of potassium dihydrogen phosphate buffer (15 mM, pH 3.2) and acetonitrile (70:30, v/v) as the mobile phase, at a flow rate of 1.0mL/min. The UV detector was set at 210nm. Retention times were 4.10, 5.30 and 6.70 min for lamotrigine, felbamate and I.S., respectively. Calibration curves were linear (mean correlation coefficient > 0.999 for both the analytes) over a range of 26.0-15000.0 ng/mL for lamotrigine and 230.0-80000.0 ng/mL for felbamate. Both intra and inter-assay precision and accuracy were lower than 8.17% for both the analytes. Absolute recoveries ranged between 94-97%. No interferences from either endogenous plasma components or other commonly prescribed antiepileptic drugs and analgesics were observed. This reliable method can be applied to pharmacokinetic investigations, bioequivalence, overdose, drug-drug interaction and therapeutic drug monitoring studies where small sample sizes are available e.g. pediatrics samples.