Evaluation of a New Immunoassay for Determination of Phenytoin and Phenobarbital: Results of a European Collaborative Control Study

Abstract

The performance of a new enzyme multiplied immunoassay technique (EMIT) was compared with other current methods, namely gas-liquid chromatography and thin-layer chromatography, for the determination of phenytoin and phenobarbital in serum. Forty-three serum samples were sent as unknowns to the participating laboratories for determination. The precision of repeated determinations was very similar for EMIT and chromatography. There was good agreement among gas chromatography, thin-layer chromatography, and EMIT results. Interlaboratory variability was lower for EMIT determinations of both antiepileptic drugs. The rapid analysis of small samples, made possible by the EMIT system, could have beneficial effects on the treatment of epilepsies.

Value of saliva samples in monitoring carbamazepine concentrations in epileptic patients

“…This was done at latest 3 weeks after sampling. Concentrations of CBZ in saliva and serum were measured employing the EMIT antiepileptic drug assay method (Schmidt et al 1977, EMIT prospectus 1978. The EMIT assay is a homogenous enzyme immunoassay method where small amounts (50 p1) of serum or saliva are mixed with a solution of antibodies against CBZ, and a substrate for the enzyme glucose-6-phosphate dehydrogenase.…”

A New Centrifugal Filtration Device for Free Drug Separation

“…Total and free drug concentrations were measured both by the enzyme multiple immunoassay technique (EMIT) (Syva) according to the published methodology (Schmidt et al, 1977), utilizing their calibrators and reagents, and by gas-liquid chromatography (GLC), utilizing an on-column methylation technique (Dudley et al, 1977). Both regular and low-level EMIT calibrators were utilized.…”

Drug determinations in body fluids by the enzyme multiplied immunoassay technique (EMIT®)

“…The first single drugs, that could quantitatively be analysed by the EMIT method, were phenobarbital and phenytoin. Since 1974, when the first antibodies and drugs-enzyme complexes became available, considerable experience with these determinations has accumulated (pippenger et al, 1975, Schmidt et al, 1976, Krugers Dagneaux et al, 1973, Belfield et al, 1977. In the meantime, assays for primidone, carbamazepine and ethosuximide have been performed, all using the same protocol.…”

“…Comparison of gaschromatographic methods with the EMIT assays yields favorably corresponding results (Pippenger et al, 1975, Krugers Dagneaux et al, 1977, Sun and Walwick, 1976. In a European control study 39 identical samples were analysed by several laboratories using the EMIT method and the common GC method for each laboratory (Schmidt et al, 1976). Interlaboratory variations appeared smaller for the EMIT results than for those obtained by GLe.…”