Anticonvulsant serum levels are useful only if the physician appropriately uses them: an assessment of the impact of providing serum level data to physicians.

The ability to measure serum levels of anticonvulsants has been a significant advance in the treatment of epilepsy. This technique enables practitioners to monitor a patient's plasma concentration, to detect potential toxicity, and to assess compliance with the prescribed regimen. A retrospective study of 164 adults with epilepsy was conducted to evaluate how serum anticonvulsant determinations were used by physicians in their treatment of epilepsy. Results indicate that the availability of test results did not improve the degree of seizure control, nor did it diminish patient reports of toxicity. In 17% of therapeutic decisions, prescribers did not appear to use the blood levels appropriately in their therapeutic decision-making process. When physicians did appropriately utilize information from serum levels, the degree of seizure control improved significantly compared with when the prescribers did not use this information. The cost of determining serum levels of anticonvulsants is justified only if the information is appropriately utilized.