SimultaneousMeasurementof Ethosuximide,Primidone,Phenobarbital, Phenytoin,Carbamazepine,and Their BioactiveMetabolitesby Liquid Chromatography

A simple, isocratic liquid-chromatographic method was de-veloped for simultaneously measuring ethosuximide, primi-done, phenobarbital, phenytoin, carbamazepine, and their bioactive metabolites within 10 mm. The chromatographic system involves a Waters ’ Radial-NOVA PAK C18 reversed-phase column and acetone/methanol/acetonitnle/1 0 mmol/L phosphate buffer (10/21/8/61 by vol, pH adjusted to 7.95 with NaOH) as mobile phase. The antiepileptic drugs are extract-ed from 50.tL of serum by mixing with 50 rL of acetonitrile containing 10 mg of tolybarb per liter as internal standard. After centrifugation, 20 L of the supemate is injected onto the column and eluted with mobile phase at the rate of 2.8 mL/min at ambient temperature. The column effluent is monitored at 200 nm. The method can detect the five antiepileptic drugs in concentrations as low as 0.5 mg/L