Determination of phenobarbital and phenytoin in serum by a mechanized enzyme immunoassay (EMIT) in comparison with a gas-liquid chromatographic method.

The antiepileptic drugs phenobarbital and phenytoin were determined in serum by enzyme immunoassay (Emit, Syva Corp.) and gas-liquid chromatography. The Emit assays were mechanized by the use of an Eppendorf analyzer 5010. The precision of the Emit system was sufficient (coefficient of variation within series 6-13% and from day to day 8-15% with various calibrators and control sera). Moreover the Emit method is rapid, specific and easy to perform. The procedure requires only 10 microliter of serum per determination. A disadvantage however is the high cost of the reagents. A comparison of the results obtained by Emit and gas-liquid chromatography in a series of about 50 patients showed a good correlation between both methods (correlation coefficient r = 0.968 for phenobarbital and 0.978 for phenytoin).