DEVELOPMENT AND VALIDATION OF CARBAMAZEPINE PLASMA CONCENTRATIONS MEASUREMENT AND ITS APPLICATION ON EPILEPSY PATIENTS

Objective: To develop and validate high-performance liquid chromatography with photodiode array (HPLC-PDA) detector as a method for measuring carbamazepine plasma concentrations in epilepsy patients treated with monotherapy or polytherapy.Methods: Carbamazepine was extracted from epilepsy patients' plasma through liquid-liquid extraction, using protein precipitation with chloroform. Analysis was performed using HPLC with Inertsil DS-4 C18 (4.6x150 mm), 5 μm particle size column. The optimal condition for separation was established in a mobile phase consisting of acetonitrile: water (50:50) at a flow rate of 1.0 ml/min, detected by PDA detector at 220 nm. Propylparaben was used as the internal standard. The retention time was 3.5 min.Results: Linearity was obtained over a concentration range of 0.5-16 μg/ml with r = 0.999. The method showed good intra-and inter-day precision and accuracy of more than 90% difference (% diff) and 95% relative standard deviation (RSD). Lower limit of quantification (LOQ) was 0.5 μg/ml and lower limit of detection (LOD) was 0.2 μg/ml with 100% accuracy and more than 90% precision. Recovery test was nearly 100%. Stability of carbamazepine plasma concentration in 3 epilepsy patients was measured on the first and third month of treatment, ranging between 83.5 to 98.7%. When used to compare carbamazepine as a monotherapy versus polytherapy, the method showed good selectivity.Conclusion: The present HPLC method was valid for measuring carbamazepine plasma concentrations in epilepsy patients treated with monotherapy or polytherapy. This method meets the standard in the EMEA guideline in terms of linearity, precision, and accuracy, also selectivity in epilepsy patients treated with polytherapy