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.