Long‐term efficacy and safety of adjunctive extended‐release oxcarbazepine (Oxtellar XR(®)) in adults with partial‐onset seizures

OBJECTIVE: To evaluate long‐term outcomes of adjunctive therapy with SPN‐804 (Oxtellar XR(®), Supernus Pharmaceuticals), an extended‐release tablet formulation of oxcarbazepine (OXC), in adults with refractory partial‐onset seizures. METHODS: After completing a 16‐week double‐blind, placebo‐controlled trial of SPN‐804 at fixed dosages (1200 or 2400 mg QD), patients entering this open‐label extension study were converted in blinded fashion to 1200 mg QD SPN‐804 as a target starting dose for long‐term treatment. Patients were followed for 1 year, during which SPN‐804 dosages could be adjusted up to 2400 mg/day according to clinical response. RESULTS: Of 214 patients, 84% completed 1‐year open‐label treatment. Median maintenance SPN‐804 dosage was 1200 mg; <10% of patients required 2400 mg. Median 28‐day seizure frequency reduction from baseline was 59%; seizure frequency was reduced ≥50% in 58% of patients; 11% were seizure free ≥6 months; and 5% were seizure free ≥1 year. SPN‐804 was discontinued due to adverse events in 5% (n = 10). Incidences of each of the most common adverse events (dizziness, headache, diplopia, nausea, vomiting, balance disorder, blurred vision) were ≤15% during 1‐year follow‐up and occurred most frequently in patients previously naïve to SPN‐804. No new safety signals, no clinically significant changes in health status, and no deaths attributable to SPN‐804 were observed. CONCLUSION: SPN‐804 administered once daily for 1 year was effective as adjunctive therapy in improving seizure control and maintaining therapeutic response in adults with refractory partial‐onset seizures. With dosage flexibility, SPN‐804 was well tolerated.