Levetiracetam in children with refractory epilepsy: Lack of correlation between plasma concentration and efficacy

PURPOSE The goals of this study are to evaluate the efficacy and tolerability of levetiracetam (LEV) as add-on therapy in children with refractory epilepsies and to determine the value of LEV blood level monitoring in this population. METHODS Sixty-nine children (39 males and 30 females) treated with LEV between 2006 and 2007 were selected. Their medical files were reviewed for LEV efficacy and tolerability. In a subgroup of children currently taking LEV, plasma concentrations were determined by high performance liquid chromatography by ultraviolet detection (HPLC-UV) method and correlated with the given dose per kilo as well as clinical response. RESULTS Fifty-one patients (74%) had a more than 50% reduction in seizure frequency with 16 patients (23%) becoming seizure free on LEV. Eighteen (26%) patients had a less than 50% reduction in seizure frequency. Adverse events due to LEV ranged from mild to moderate in only 18 patients (26%). The most frequently observed were drowsiness, behavioral difficulties, increase in seizure frequency and headaches. The majority (60.5%) of the responders received doses between 10 and 50mg/kg/day and had a plasma concentration (PC) between 5 and 40microg/ml. However, we found no clear correlation between PC and efficacy. CONCLUSION Levetiracetam given twice a day in children with refractory epilepsy reduces seizure frequency in all types of epilepsy. In children, LEV is a broad spectrum anticonvulsant with a favourable safety profile.