Semi-automated continuous-flow enzyme immunoassay for antiepileptic drugs in serum

We have developed a semi-automated method for measuring five kinds of antiepileptic drugs in serum by successfully adapting commercial competitive-binding enzyme immunoassay kits (MARKIT; Dainippon) for use with a continuous-flow analyzer (Technicon AutoAnalyzer II equipped with a dialyzer). The free enzyme-labeled drug is automatically separated by a microfilter from the competitive immunoreaction mixture between labeled and unlabeled drug for anti-drug immunoglobulin coupled to bacterial cell walls. The concentrations of the antiepileptic drugs in serum samples can be determined by automated measurement of enzyme activity of the enzyme-labeled drugs. Results of the semi-automated method correlated well with those obtained by manual enzyme immunoassay, gas-liquid chromatography, and "high-pressure" liquid chromatography. The correlation coefficients were all greater than 0.95, showing the practicality of this method for therapeutic monitoring of antiepileptic drugs.