Abstracts

Rationale: To assess effectiveness of two commonly used antiepileptic drugs (AED) for new onset focal epilepsy in children, using drug failure rate as the primary outcome measure. Methods: We conducted a retrospective cohort study of children ages 1 to 17 years with new onset focal epilepsy presenting to a single referral center between January 2008 and June 2010. Potential subjects were identified through billing codes and eligibility was confirmed by subsequent review of electronic medical records. Exclusion criteria included status epilepticus or hospitalization for greater than 48 hours at presentation, and less than 6 months of follow up information available. Differences in baseline characteristics between treatment groups were evaluated using t-tests and chi-square tests. Kaplan-Meier methods were used to estimate the rates of drug failure, defined as discontinuation of first AED or addition of a second AED. Factors potentially influencing time to failure (including reason for failure, age at presentation, presence of co-morbid conditions, and epilepsy etiology) were evaluated using Cox proportional hazards models. Results: Of 291 patients meeting inclusion criteria, 220 were initiated either on levetiracetam (LEV, n=93) or on oxcarbazepine (OXC, n=127). Median age at first clinic visit was 7.3 years (range 1.2-17 years), and 53.6% of subjects were male. Treatment groups were similar with respect to age, sex, presentation to ER or hospitalization at time of diagnosis, presence of co-morbid conditions, and presence of EEG abnormalities. The study comprised 1429 person-treatment months for LEV and 2140 person-treatment months for OXC. Amongst all subjects, probability of remaining on the first AED was 76% at 6 months, and 58% at 40 months. Drug failures due to lack of tolerability occurred sooner (median time 1.7 months) compared to failures due to lack of efficacy (median time 4.56 months). Time to drug failure was shorter in patients on LEV (p=0.04, log rank test), and this was accounted for by the higher number of tolerability failures for LEV (19 of 93) compared to OXC (16 of 127). Rate of drug failure was 2.8 per 100 person months for LEV and 1.7 per 100 person months for OXC (hazard ratio 1.6, p=0.04). No other factors influenced differences in drug failure rates. Conclusions: Overall, LEV and OXC are effective medications for treatment of new onset pediatric epilepsy, with the majority of patients continuing on monotherapy with the first drug for two years. Most drug failures occurred within the first six months, and tolerability failures occurred earlier than efficacy failures. OXC had a lower failure rate than LEV, a finding primarily related to tolerability. These data may help guide AED choice for children with new onset focal epilepsy.