title: Simultaneous determination of phenytoin and phenobarbital in serum or plasma by substrate-labeled fluorescent immunoassay.
abstract: This assay system for simultaneously determining phenytoin and phenobarbital in serum and plasma is based on the substrate-labeled fluorescent immunoassay technique. A beta-galactosylcoumarin derivative of phenobarbital and a 4-methylcoumarin phosphodiester derivative of phenytoin are used as substrate labels for Escherichia coli beta-galactosidase and Crotalus atrox phosphodiesterase I, respectively. The smallest measurable concentrations are about 1.6 mg/L for phenytoin, 2.7 mg/L for phenobarbital. Within-run coefficients of variation are about 5% for phenytoin and 2% for phenobarbital, about 6% for both between-runs. Results for phenytoin and phenobarbital in serum and plasma correlate well with those determined by the Ames TDA (r = 0.944 and 0.986, respectively) and Syva's EMIT (r = 0.977 and 0.969, respectively) assays.
mesh_terms: D006801:Humans; D006863:Hydrogen-Ion Concentration; D007124:Immunoenzyme Techniques; D010634:Phenobarbital / Q000097:blood*; D010672:Phenytoin / Q000097:blood*; D010727:Phosphoric Diester Hydrolases; D013997:Time Factors; D001616:beta-Galactosidase
chemical_list: D010672:Phenytoin; D010727:Phosphoric Diester Hydrolases; D001616:beta-Galactosidase; D010634:Phenobarbital