We developed a simple and sensitive method using reversed-phase high-performance liquid chromatography (HPLC) for determining lamotrigine (LTG) plasma concentrations in infant patients with epilepsy undergoing polypharmacy.It involves a simple protein precipitation procedure that uses no solid-phase or liquid-liquid extraction.HPLC was carried out on a Cadenza CD-C 18 column (3μm,4.6 mm×150 mm) with phosphate buffer (pH 4.6;25 mM) containing a methanolacetonitrile mixture (4:3,v/v) as the mobile phase,by gradient elution at a 1.0 mL/min flow rate.LTG was detected using a UV detector at 215 nm.The quantification limit was 0.10μg/mL for 100μL of plasma sample.The intra- and interassay coefficients of variation were 1.18-6.87% and 1.65-7.07%,respectively.A specificity and selectivity study showed that there were no interfering peaks.In addition,correlation analysis conducted on LTG concentrations by the new method and a commercial HPLC method produced a correlation coefficient (r ) of 0.9974.
