Clinical pharmacokinetics of carbamazepine.

The relationship between daily dose and plasma levels of carbamazepine is poor. The slope of that relationship varies with the patient population. Children require twice as much of the drug as adults do to achieve a given level. Also, dosage requirements increase in the presence of other drugs that are enzyme inducers. Recent reports suggest that the 10,11-epoxide metabolite of carbamazepine can contribute to the neurotoxicity attributed to carbamazepine. Carbamazepine is a broad-spectrum enzyme inducer. Three reports in the past 2 years show that haloperidol levels are reduced by approximately 50% when carbamazepine is introduced. Those interactions may complicate the interpretation of clinical trials of carbamazepine.