Evaluation of safety in exceeding maximum adult doses of commonly used second-generation antiepileptic drugs in pediatric patients

OBJECTIVE Pediatric patients often require larger doses of antiepileptic drug (AED) than adults in order to attain therapeutic serum concentrations and/or achieve seizure control. Safety and efficacy data are often extrapolated from adult literature; hence, optimal dosage may only be determined anecdotally or based on expert opinion. With limited pediatric dosing guidelines, milligrams per day that are based on weight may exceed the maximum adult dose. The primary objective of this study is to evaluate the safety of exceeding maximum doses as specified by the US Food and Drug Administration or manufacturers of commonly used AEDs in pediatric patients. METHODS This study is a single-center, retrospective analysis of all pediatric patients seen in the outpatient clinic between October 2010 and October 2014 who were prescribed a dose that exceeds the maximum approved dose of oxcarbazepine, zonisamide, topiramate, levetiracetam, lamotrigine, or clobazam. Baseline demographics (ie, sex, age, race/ethnicity, weight, height, diagnosis), serum drug concentrations, and appropriate laboratory tests were collected. Side effects were reviewed. RESULTS During the 4-year study period, 41,137 prescriptions were included. A total of 2% of prescriptions exceeded the maximum dose of 1 of the included AEDs. The most common AED prescribed above the maximum dose was levetiracetam (53%), whereas lamotrigine was the least common (6%). The largest doses prescribed exceeded the maximum by 3-fold (i.e., levetiracetam dose of 9000 mg/day). CONCLUSION It appears safe to use doses exceeding the maximum approved dose of the evaluated AEDs in pediatric patients, with appropriate counseling and monitoring for adverse effects.