SIMULTANEOUS DETERMINATION OF THE ANTICONVULSANTS, CINROMIDE (3-BROMO-N-ETHYLCINNAMAMIDE), 3-BROMOCINNAMAMIDE, AND CARBAMAZEPINE IN PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A high-performance liquid chromatographic method is described for monitoring plasma concentrations of cinromide (3-bromo-N-ethylcinnamamide) and its de-ethylated metabolite. Carbamazepine levels can be measured by the same technique. The N-isopropyl analog of cinromide is used as an internal standard and all compounds are separated on a reversed-phase column operated at 55.degree. C with a small-diameter pre-column maintained at the same temperature. The extraction is rapid and generally applicable to plasma and urine samples [from epileptic patients] that are to be analyzed by reversed-phase chromatography. Short- and long-term reproducibility studies show less than 4% relative standard deviation for replicate determinations for all drugs. Limits of quantitation are 10-20 ng/ml with an internal standard concentration of 3 .mu.g/ml. 3-Bromocinnamic acid, a cinromide metabolite which may have some anticonvulsant effect, can be analyzed simultaneously by buffering the mobile phase and adding an ion-pairing reagent.