Effect of carbamazepine or phenytoin therapy on blood level of intravenously administered midazolam: a prospective cohort study.

Dental treatment of intellectually disabled patients is frequently performed under general anesthesia or sedation. Many of these patients have epilepsy and are medicated with antiepileptic drugs (AEDs). Carbamazepine (CBZ) and phenytoin (PHT) are known to promote the metabolism of midazolam, and the blood levels of midazolam in patients medicated with CBZ or PHT may be different from those in healthy individuals. In this study, we clarified the influences of CBZ and PHT on the blood level of intravenously administered midazolam in patients medicated with CBZ or PHT. The subjects were divided into the following groups: not medicated with AEDs (control group), medicated with only CBZ or PHT (mono CBZ/PHT group), and medicated with CBZ or PHT or both and other AEDs (poly CBZ/PHT group). General anesthesia was achieved using midazolam, propofol, and remifentanil, and then the blood midazolam level was measured at 10, 30, and 60 min after intravenous midazolam administration. According to the results, the blood midazolam level was significantly lower in the mono and poly CBZ/PHT groups than in the control group. This finding suggests that intravenously administered midazolam may have a weaker effect in patients medicated with CBZ or PHT.