Abstracts

It has been established that carbamazepine withdrawal is associated with more severe seizures than withdrawal of other classical antiepileptic drugs. Oxcarbazepine (OXC) has structural and some functional similarities to carbamazepine. It is not known if OXC is similar to carbamazepine in associated withdrawal seizures. We identified all epilepsy patients admitted to the epilepsy monitoring unit (EMU) on OXC monotherapy between 2000 and 2004. As a control group, we identified all patients who were admitted to the EMU on phenytoin (PHT) monotherapy in the same period of time. AEDs were usually discontinued on day 1 or 2 of admission. For each patient we recorded pre-admission seizure frequency for each seizure type, as well as the number and type of seizures recorded in the EMU. We calculated seizure frequency for complex partial seizures (CPS) and generalized tonic clonic seizures (GTCS) before admission and during monitoring, and calculated the relative change in frequency for each seizure type. We compared the OXC and PHT groups for the above parameters. Twelve epilepsy patients were admitted to the EMU on OXC monotherapy and 11 on PHT monotherapy. Five patient in the OXC group had no prior history of GTCS; one of these had one during monitoring. Seven had prior GTCS and 4 of them had GTCS in the EMU. For the whole group there was a 59 fold relative increase in frequency of GTCS during monitoring. The average frequency of complex partial seizures surprisingly did not change. In the phenytoin group, there were 2 patients who never had GTCS. Only 3 patients had GTCS in the EMU, all of them with prior history of GTCS. Overall, there was a 10.6 fold relative increase in GTCS frequency and a 6.5 fold increase in CPS frequency in the EMU. Oxcarbazepine withdrawal appears to be associated with a greater increase in GTCS frequency than phenytoin withdrawal. Oxcarbazepine withdrawal in the EMU should be handled with caution.