Cost-effective assays for use in monitoring carbamazepine, phenobarbital, and phenytoin in serum.

Using Syva "EMIT" reagents and the Cobas Bio centrifugal analyzer, we have developed cost-effective assays for therapeutic drug monitoring of carbamazepine, phenobarbital, and phenytoin. With these optimized methods one can assay up to 2470 samples with a single 100-test EMIT kit with good precision and accuracy. Between-batch CVs, based on results of repeat analysis of routine patients' samples, were 4.6%, 7.0%, and 5.3%, respectively. Results correlated well with those by methods previously used [gas chromatography and fluorescence polarization (Abbott TDx)], but there was a negative bias (-10.9%) of our method for phenobarbital results in patients' samples, as compared with those obtained with the TDx.