Application of substrate-labelled fluorescent immunoassay to the measurement of anticonvulsant and antiasthmatic drug levels in plasma and serum.

: The use of the Ames homogeneous Substrate-Labelled Fluorescent Immunoassay is described here. It performed easily and accurately across the therapeutic and low toxic ranges with the drugs phenytoin, phenobarbital, primidone, carbamazepine, and theophylline, and also at high toxic levels subsequent to prior sample dilution. The assay performed well in comparison to the standard assays of gas-liquid chromatography, radioimmunoassay, and enzyme immunoassay, and showed no problems with lipaemic, icteric, or, particularly, uraemic specimens.