Removal of 10-hydroxycarbazepine by plasmapheresis

Removal of the oxcarbazepine metabolite 10-hydroxycarbazepine (MHD) by plas mapheresis was evaluated during a series of six plasmaphereses of a 13-year -old boy with Rasmussen encephalitis. Plasmapheresis was performed after st eady-state concentrations of MHD had been achieved with a dose of 2550 mg o xcarbazepine daily. The mean amount of MHD removed per plasmapheresis was 7 8.9 mg (SD: 6.0 mg), representing 3% to 4% of the daily oxcarbazepine dose and approximately 5% to 6% of body stores of MHD. The mean steady-state tro ugh MHD concentration was 33.3 mg/L (SD: 1.8 mg/L), and this was remarkably stable during the entire plasmapheresis period. The serum concentration of MHD) was only mildly reduced by the procedure. The areas under the concent ration curve of MHD) on the first and sixth day of plasmapheresis were, 99% , and 94%, respectively, of the pre-plasmapheresis values. The results are in agreement with studies on other anticonvulsant medications (carbamazepin e, valproic acid, phenobarbital, and phenytoin), indicating that minor frac tions (2% to 10%) of body stores of these drugs are depleted during plasmap heresis. The authors conclude that it is unnecessary to adjust the oxcarbaz epine dosage when performing single-volume plasma exchanges or even multipl e exchanges during an extended period. It is further proposed that plasmaph eresis is unlikely to be of therapeutic benefit in the treatment of an oxca rbazepine overdose.