ABSTRACT
Background Therapeutic drug monitoring (TDM) is the process of measuring drug level in body fluids. It is done to maintain plasma concentration of the drug under therapy within a specific target range for maximum therapeutic efficacy without unnecessary exposure to adverse effects. Objective This study aims to evaluate necessity of therapeutic drug monitoring in Phenytoin, Carbamazepine and Lamotrigine therapy among epileptic patients. Method A prospective, cross-sectional study was conducted for a period of one year at BP Koirala Institute of Health Sciences, Dharan, Nepal. After taking detailed history, blood samples were collected from epileptic patients on monotherapy with the selected drugs. Plasma levels of these drugs were analyzed using High Performance Liquid Chromatography technique (HPLC). Out of total 42 selected patients, 21 were tested for phenytoin, 17 for carbamazepine and four for lamotrigine. The result was categorized into therapeutic, sub-therapeutic and above-therapeutic groups based on reference range. Result Out of total 21 samples tested for phenytoin, 15(71.4%) had plasma drug level within therapeutic range, 5(23.8%) had within subtherapeutic range and 1(4.8%) had above therapeutic range. Analysis of carbamazepine plasma level showed 14(82.3%) at therapeutic level, 1(5.9%) at sub-therapeutic level and 2(11.8%) at above-therapeutic level. Lamotrigine testing in four samples showed 2(50% in) both within therapeutic range and above-therapeutic range. Conclusion Therapeutic drug monitoring of phenytoin, carbamazepine and lamotrigine showed variation in plasma level irrespective of the therapeutic dose. It is suggested that dose adjustment of antiepileptic drugs should be done after establishing 'individual therapeutic range' following regular plasma monitoring.
