Simultaneous determination of eleven antiepileptic compounds in serum by high-performance liquid chromatography

A high-performance liquid chromatographic method for the simultaneous determination of carbamazepine, CGP 10 000 (a common metabolite of carbamazepine and oxcarbazepine), desmethylmephenytoin, 10,11-epoxycarbamazepine, ethosuximide, GP 47 779 (the active metabolite from oxcarbazepine, a new drug made by Ciba-Geigy), mephenytoin, phenylethylmalonamide, primidone, pheneturide, phenobarbital and phenytoin is described. The serum is extracted with ethyl acetate at pH 3.9 and the dried extract is dissolved in 70% ethanol in water and an aliquot is injected into a Hewlett-Packard 1084 B liquid chromatograph. A reversed-phase (RP-8) column is used with acetonitrile and water as the mobile phase. The eluted drugs are detected at 207 nm. The recovery of the compounds varies from 76% to 95% with the day-to-day precision (C.V.) between 3.8% and 9.8%, the within-day precision between 1.8% and 5.8% and run-to-run precision between 1.0% and 2.6%.