Clinical relevance of therapeutic drug level estimation with respect to clonazepam and carbamazepine: preliminary report.

This paper compares the results of plasma drug level estimations for 30 patients receiving clonazepam and 39 patients taking carbamazepine (assessing total and free carbamazepine concentrations together with carbamazepine epoxide levels) with the clinical features of seizure control. Owing to the small numbers of seizure-free patients, the power of the study was insufficient to justify absolute conclusions being drawn. However there appeared to be a trend which suggested that drug level estimations in both situations had virtually no clinical relevance. This causes one to question the growing reliance on plasma drug level estimation in the treatment of epilepsy and, because of the low power of the study, demands extension of the work to confirm its significance. This type of research in epilepsy, based exclusively on a secondary and tertiary referral source, has inherent difficulty in that a conspicuously low number of well controlled patients is included. Acknowledgement of this fact should lead one to appraise critically other papers giving dogmatic statements regarding therapeutic ranges of anticonvulsant plasma levels.