[Polarographic determination of some phenylsubstituted anticonvulsants]

A method is described to determine the anticonvulsive drugs phenobarbital, phenytoin, mephenytoin, methylphenobarbital and primidone. A serum extract is nitrated, separated by thin-layer chromatography, and the nitro compounds are determined by polarography. The rates of recovery are: phenobarbital 81%, phenytoin 79%, mephenytoin 80%, methylphenobarbital 86% and primidone 84%. The sensitivity limits range from 3.5 mug/ml plasma for phenytoin to 5.5 mug/ml for mephenytoin and methylphenobarbital. This method might be useful not only for determination of therapeutic blood levels but also for toxicology because it saves time and the expenditure of work is small. The mean deviation for mononitrated anticonvulsive drugs is +/- 2.8% (for 50 mug/ml) and +/- 11.6% (for 10 mug/ml). For phenytoin being dinitrated, the values are +/- 0.6% and +/- 7.5% for 50 mug and 5 mug, respectively). We determined blood levels of out-patients containing phenobarbital and phenytoin besides other substances. Having once established calibrating curvers internal or external standards are not required.