Therapeutic progress: review IV. Therapeutic drug monitoring: can it improve the treatment of epilepsy?

Our ability to measure plasma drug concentrations under steady-state conditions has meant that the daily dose of phenytoin, and a few other anticonvulsants drugs, can be safely adjusted to suit the individual epileptic's seizure pattern and drug metabolizing capacity. With correct timing of samples and interpretation of results, therapeutic drug monitoring can lead to, and maintain, complete freedom from seizures for some patients and an appreciable reduction in frequency for many others. There are large numbers of epileptics, however, who continue to suffer needlessly because clinical practice has lagged behind our expertise in drug assay and our understanding of pharmacokinetics. We are not using our knowledge sufficiently to benefit the epileptic population as a whole.