Temporal pattern of oxcarbazepine and phenytoin withdrawal seizures during epilepsy monitoring

Summary 

Purpose

To compare the temporal pattern of seizures after acute withdrawal of oxcarbazepine (OXC) and phenytoin (PHT) in the epilepsy monitoring unit (EMU).

Methods

We identified all epilepsy patients admitted to our EMU on OXC or PHT monotherapy, over a period of 5 years. The OXC taper usually occurred over 2 days while PHT was abruptly discontinued on admission day. For each patient, we recorded the number and type of seizures for each EMU day. We used Poisson regression models to estimate daily seizure frequency separately for complex partial seizures (CPSs) and generalized tonic–clonic seizures (GTCSs).

Results

Forty patients were admitted on OXC and 32 on PHT monotherapy. The temporal distribution of seizures varied between the two groups. The first GTCS was more likely to occur in the first 2 days of monitoring for the OXC group (p<0.046). There was a higher frequency of GTCS on day 2 of admission in the OXC group (p=0.011). The groups did not differ in the pattern of CPS.

Conclusions

OXC is disproportionately associated with increased GTCS in the first 2 days after acute withdrawal. The early peak of GTCS favors a rebound phenomenon in addition to loss of therapeutic effect.

Keywords: Withdrawal seizures, Epilepsy monitoring, Rebound phenomenon, Oxcarbazepine, Phenytoin