Abstract

The addition of voriconazole to chronic treatment with carbamazepine 400 mg twice a day was associated with increased carbamazepine serum levels (14.1 mg/l) and serum concentration dose ratios. Three days after the voriconazole was started, this ratio doubled its value to 1. Carbamazepine concentration as well as serum concentration dose ratio gradually decreased after treatment with voriconazole was discontinued, suggesting a probable interaction between the two drugs, according to the drug interaction probability scale. Although no clinical toxicity appeared with carbamazepine, the interaction can be considered severe and potentially toxic: early detection, suspension of carbamazepine and dose adjustment prevented such harm in this case. The likely mechanism is that voriconazole decreases carbamazepine metabolism. To our knowledge this is the first reported case of interaction between voriconazole, as precipitant drug, and carbamazepine, as object drug. The interaction is not referenced in clinical databases as published cases, but as a foreseeable interaction. Publication of this first clinical case reinforces the need of using both drugs associated with caution.

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