Abstracts

RATIONALE:Oxcarbazepine (OXC)is a novel antiepileptic drug which structurally resembles carbamazepine (CBZ). It was felt that due to the similarity, patients could be switched from CBZ to OXC rapidly with side effects and difficulties kept to a minimum. METHODS:The initial 15 consecutive patients started on OXC at The Comprehensive Epilepsy Care Center for Children and Adults were evaluated. 5 patients were converted overnight from CBZ to OXC, 3 were converted over several days, and 7 patients had OXC added on to other concomitant AEDs other than CBZ. RESULTS:Seizure frequency worsened in 1 of the 5 patients converted overnight to OXC but improved with a higher dosage. All of the other patients had no worsening of seizures. It is too early to yet predict the overall improvement rate with OXC. 3 out of 5 patients with overnight conversion noted some dizziness. 1 out of 3 patients with slow conversion noted dizziness. 6 out of 7 patients with startup as in the Physicians Desk Reference (PDR) labeling, at 300mg bid for 1 week and then 600mg bid, noted dizziness. Most side effects could be eliminated with lowering the OXC dosage or lowering concomitant AEDs. Those being converted overnight to OXC averaged 900mg per day CBZ and were converted to an average of 1620mg per day OXC (1.8 times the CBZ dosage). Those being converted slowly averaged 667mg per day CBZ and 1000mg when on OXC (1.5 times the CBZ dosage). Those taking other AEDs with CBZ were usually started at 300mg bid times 2 weeks then 600mg bid. More side effects of higher intensity were noted with the latter titration. CONCLUSIONS:The higher conversion ratio of 1.8 times (OXC/CBZ) with the overnight conversion versus 1.5 times with the slow conversion may have explained some of the slightly greater dizziness with overnight conversion. Overnight conversion from CBZ can usually be accomplished without significant difficulties. If one aims for higher dosages than 1.5 times the CBZ, some additional dizziness may be noted. If side effects are noted this can usually be improved by decreasing the OXC. Initial titration of OXC without CBZ may need to be done slightly slower than the PDR recommendations. However, OXC can be safely added to patients taking CBZ or other concomitant AEDs.