Abstracts

Partial epilepsy is typically managed initially by monotherapy with anti-epileptic drugs (AEDs). Patients refractory to AED monotherapy may be switched to monotherapy with another AED or another AED may be added to the current AED. This retrospective study was designed to assess the economic costs of switching patients refractory to initial non-oxcarbazepine AED monotherapy to oxcarbazepine (OXC) monotherapy (Cohort A), compared with the costs of add-on therapy (Cohort B). Data from the PharMetrics integrated medical and pharmacy claims database, which includes 57 managed care plans, were collected for adult patients who were receiving treatment with AEDs between January 1, 2000 and March 30, 2002. Patient data were analyzed over 6 months prior to treatment failure with either carbamazepine, phenytoin, or valproic acid, and post-failure defined as 12 months after switching to OXC monotherapy (Cohort A) or add-on therapy (Cohort B). Total treatment costs were compared within each cohort pre- and post-failure and between cohorts, with statistical differences tested using Wilcoxon rank sum tests. Multivariate econometric analyses of cost examined the impact of cohort, controlling for age, gender, geographic location, Charlson comorbidity score, and specific comorbidities. Data from a total of 169 and 380 patients were reviewed in cohorts A and B, respectively. Demographic and clinical characteristics were statistically similar between cohorts. Annual treatment costs rose for both groups during the post-failure period (p[lt]0.01). Pre-failure costs were not different between cohorts, however post-failure costs for cohort B were higher than for cohort A (p[lt]0.10). The mean increase in the cost of overall care was lower for Cohort A at $1,248 (SD $15,174) compared with Cohort B at $1,806 (SD $17,827). Although not statistically significant, a switch to OXC monotherapy was associated with an average annual savings of $558, compared to add-on therapy. Pharmacy cost constituted 31.2% and 42.9% of the total costs during the post-failure period for Cohort A and Cohort B, respectively. Additionally, Cohort B was nearly twice as likely as Cohort A to have an emergency room (ER) visit during the post-index period (OR=1.89, p=0.08). These analyses suggest that, for patients refractory to initial standard AED monotherapy, e.g. carbamazepine, phenytoin, or valproic acid, switching to OXC monotherapy may provide a less costly alternative for managed care organizations than add-on therapy. Switching to OXC monotherapy also may be associated with fewer ER visits as well as lower pharmacy costs. (Supported by Novartis Pharmaceuticals Corporation)