OBJECTIVES: Patients refractory to initial anti-epileptic drugs (AEDs) monotherapy undergo a change in their therapeutic regimen. This study sought to compare the economic costs of care of patients refractory to initial AED therapy was not oxcarbazepine (Trileptal®), who were switched to oxcarbazepine (OXC) monotherapy and stayed on OXC for an entire 12 months follow-up (Cohort A), compared with the costs of the patients who failed to be on the same therapy within 1 year (Cohort B). METHODS: Retrospective data from PharMetrics integrated medical and pharmacy claims database, which includes 57 managed care plans, were analyzed. Adult patients receiving treatment with AEDs between January 1, 2000 and March 30, 2002 were studied. Data were analyzed from 6 months prior to treatment failure with either carbamazepine, phenytoin, or valproic acid, and through a post-therapy period defined as 12 months after switching to OXC monotherapy. RESULTS: In all, 169 adult patients were observed; 31.4% (53/169) patients stayed on OXC for an entire year of follow-up, constituting Cohort A. A total of 116 patients (Cohort B) either switched to another drug or opted for combination therapy at some point within 1 year. Demographic and clinical characteristics were statistically similar between cohorts. Although pre-index treatment costs are similar between the 2 cohorts ($9,434 +SD $14,512 versus $9430 + $15,229), the mean cost of care in Cohort A decreased by $1123 while the mean cost rose for Cohort B during the post-failure period (p<0.01). Post-failure costs for cohort B were substantially higher than for cohort A ($8,312 +$11,218, vs. ($11,760 + $18,155, p=0.03). CONCLUSIONS: The persistent use of OXC provided a less costly alternative for managed care organizations among patients switched to OXC after initial monotherapy failure. This study finding encourages the clinical practitioner to promote patients’ persistency on the OXC monotherapy when medically appropriate.