Anticonvulsants in serum, determined with a fully mechanized enzyme analyzer

The "EMIT" enzyme immunoassay system (Syva) that involves use of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) as the enzyme label has been adapted to a fully mechanized kinetic enzyme analyzer for analysis of phenobarbital, phenytoin, and primidone. This procedure, compared with the gas-chromatographic procedure of Kupferberg [Clin. Chim. Acta 29, 283 (1970)], gave a weighted regression line--forced through the origin--of y=(1.01+/-0.04) x for phenobarbital, y=(0.95+/-0.04) x for primidone. Within-run coefficients of variation based on single determinations were 9,11, and 22% for primidone, phenobarbital, and phenytoin, respectively. Run-to-run assay CV was 6% for primidone and phenobarbital and 13% for phenytoin, based on the means of triplicate determinations of a sample with a mid-range concentration.