Monitoring of therapeutic serum concentrations of antiepileptic drugs by a newly developed gas chromatographic procedure and enzyme immunoassay (EMIT): a comparative study.

A gas chromatographic procedure for the simultaneous determination of carbamazepine, phenobarbital and phenytoin using SP 2510 DA as stationary phase is presented. The antiepileptic drugs are determined simultaneously without derivatisation under isothermal conditions by a flame ionisation detector. The gas chromatographic procedure can be easily mechanized. The coefficient of variation for the precision from day to day is 8.9% for carbamazepine, 7.0% for phenobarbital and 4.3% for phenytoin as calculated from single determinations. The deviations from the target value of spiked pool sera range from 4.3 to 9.5%. The gas chromatographic results of this method and of determinations by Dexsil 300 for primidone and SP 1000 for ethosuximide are compared with the corresponding enzyme immunoassays (EMIT). The precision of the gas chromatographic methods is somewhat better than EMIT. When patients' sera are analysed by both procedures the results show no clinically relevant differences. It can be concluded that the different methods are interchangeable and may be selected according to practical necessities.