Abstracts

The first-line antiepileptic drug (AED) oxcarbazepine (OXC) is widely used as monotherapy in the treatment of epilepsy. Although OXC as well as carbamazepine (CBZ) and phenytoin (PHT) are all sodium channel blockers (SCB), different mechanisms on the sodium channel may result in improved seizure control when a patient who fails to experience seizure control with one SCB is switched to another SCB. Other patients may respond to another AED with a different mode of action. The efficacy of OXC monotherapy in patients with partial seizures switched from other SCBs (CBZ and PHT) or valproate (VPA) was evaluated in a prospective, open-label, multicenter study. Patients aged [ge]12 years experiencing 2-40 partial seizures per month while receiving treatment with an AED in the 2 months prior to entry were included in the study. Following a 2-week screening phase, patients entered a 16-week treatment phase in which oxcarbazepine was initiated at daily doses of 8-10 mg/kg (patients [le]60 kg) or 600 mg (patients [ge]60 kg). OXC was titrated up over 4 weeks while existing AED monotherapy was concurrently tapered off. The primary efficacy variable was the change in seizure frequency during the treatment phase compared with the 3-month retrospective baseline phase during which the patients were receiving treatment with another AED. This analysis was performed with data from patients receiving the most common AEDs at study entry: CBZ, PHT, and VPA. Data from patients with seizures at baseline, who received at least one dose of OXC, and for whom at least one post-enrollment assessment was available were included in the analysis. A total of 245 patients were enrolled in this study, 176 of which had seizure data available at baseline and post-enrollment. A [gt]50% reduction in seizure frequency was observed in 48.0% to 64.9% of patients switched from CBZ, PHT, or VPA, and a 100% reduction was observed in 12.0% to 27.5% of patients. Mean seizure reductions from baseline for each AED are presented in the table below. The most common adverse events involved the CNS or gastrointestinal systems and occurred at similar frequency regardless of the AED switch. [table1] OXC monotherapy was efficacious in reducing seizure frequency in patients with partial seizures whether switching from previous treatment with the SCBs CBZ or PHT, or from VPA. The improved seizure control observed when switching patients with uncontrolled partial seizures while receiving treatment with another SCB to OXC monotherapy suggests that its mode of action may involve distinct mechanisms on the sodium channels. (Supported by Novartis Pharmaceuticals)