Abstracts

RATIONALE: Oxcarbazepine (OXC) is approved for use as mono- or adjunctive therapy to treat partial seizures in adults. Previous studies report little potential for drug interactions with OXC, suggesting it is well tolerated as add-on therapy. The rapid loading of OXC may account for the severity and frequency of side effects (SE) found in earlier reports. This study reviews titration schedules for OXC adjunctive therapy, looking at SE, compliance and seizure frequency. METHODS: A retrospective review of medical charts from the Adult Epilepsy Program at HMC identified 20 patients prescribed OXC add-on therapy. All had intractable epilepsy and had failed other antiepileptic drugs (AEDs). In ten patients OXC was advanced following the manufacturer's recommendations. The remaining ten patients were started at half the recommended dose and titrated using slower schedules. SEs were compared across schedules and differences between concomitant AEDs were evaluated. RESULTS: All patients on OXC add-on therapy had one or more SEs. Seven patients discontinued OXC due to SE severity; three were successfully restarted at slower titrations. One patient was discontinued due to fever, elevated LFTs and change in mental status. Six of the seven discontinuations were from the recommended titration schedule. Most frequent SE was vertigo, followed by diplopia, fatigue, confusion, ataxia and nausea. Occurrence of SE was highest in the quickest titration and lowest in the slowest schedule. There were no differences in frequency of SE when comparing concomitant AEDs. Seizure frequency was not affected by rate of titration. CONCLUSIONS: SEs are commonly seen with adjunctive therapy, and it is not clear from this sample which SEs can be attributed to OXC. It does appear that slower titrations of OXC increased the tolerability of the regimens. This can potentially improve the efficacy of OXC as add-on therapy if patient compliance increases. The recommended dosing schedule however, resulted in higher rates of discontinuation, lowered compliance and more SEs without showing better seizure control. Alternative dosing titrations should be investigated.