Phenacemide therapy of complex partial epilepsy in children: determination of plasma drug concentrations.

We used monotherapy with phenacemide to treat complex partial seizures in 13 children who were refractory to conventional antiepileptic drug therapy. Twelve patients responded with a reduction in seizure frequency, and 5 have been totally seizure free since the start of therapy. Phenacemide therapy was well tolerated with a minimum of untoward side effects and no evidence of irreversible drug toxicity. We developed a rapid and sensitive assay for the determination of plasma phenacemide concentrations by high performance liquid chromatography to monitor drug levels during therapy. Seizure control was achieved at plasma drug levels that ranged from 16 to 75 micrograms/ml. The median effective dose in our series was 52 micrograms/ml. The recurrence of seizures in three patients was, in each case, associated with trough plasma phenacemide levels below 50 micrograms/dl.