OBJECTIVES : Formulary restrictions may have unintended consequences: delaying or reducing likelihood of antiepileptic drug (AED) therapy initiation. This has not been studied for pediatric patients with focal seizure (FS) prescribed AED therapy. This study assessed associations between formulary restriction and time to and likelihood of successful dispensation of prescribed AED treatment among pediatric patients with FS.

METHODS : Symphony Health’s Integrated Dataverse (IDV^®) open-source claims data for 04/01/15–06/30/18 were used to identify patients with a diagnosis of FS and ≥1 new AED pharmacy claim, <18 years old, with ≥6 months of pharmacy data before and after. The index date was defined as earliest AED date that pharmacy claim was approved or rejected due to formulary restriction. Cohort assignment was also based on whether the index AED claim was approved or rejected due to formulary restriction. Proportion of patients with index AED dispensation and time to dispensation was analyzed during the 6-month follow-up period. The impact of formulary restriction on likelihood of prescribed AED’s successful dispensation was assessed using multivariable Cox proportional hazards model.

RESULTS : There were 9,529 and 3,081 patients in the approved and rejected claim cohorts, respectively. The proportion of patients with an index claim for a generic AED was higher in the approved (95.9%) vs. the rejected (88.9%) cohort. Mean (SD) time to first dispensation was 2.1 (11.9) and 7.4 (21.5) days for the approved and rejected cohort, respectively. The proportion of patients with a successful index AED dispensation at 6 months was higher in the approved (92.8%) vs. rejected (75.7%) cohort. After adjustment, formulary-related rejection of an index AED was associated with lower likelihood of its successful dispensation [hazard ratio: 0.73; p<0.001].

CONCLUSIONS : Formulary restrictions may lead to an average delay of 5.3 days and reduced likelihood of successful dispensation of AED treatment for pediatric patients diagnosed with FS.