Subtherapeutic voriconazole concentrations associated with concomitant dexamethasone: case report and review of the literature

Summary What is known and objective Voriconazole has significant drug interactions due to metabolism by CYP enzymes. Subtherapeutic voriconazole concentrations associated with concomitant dexamethasone are not well described. Case description An 84‐year‐old male was started on voriconazole for a fungal brain abscess. He was readmitted due to clinical failure thought to be the result of subtherapeutic voriconazole concentrations. Dexamethasone was identified as a potential cause due to its induction of CYP enzymes. This interaction was substantiated by sequential troughs that demonstrated a rise in voriconazole concentrations as dexamethasone was tapered off. What is new and conclusion Therapeutic drug monitoring for patients on voriconazole and dexamethasone is essential to prevent suboptimal clinical outcomes. Subtherapeutic voriconazole concentrations due to an interaction with dexamethasone are not recognized by drug interaction databases. This interaction can have a significant impact on outcomes in patients with invasive fungal infections. The following case report discusses the clinical impact of a drug–drug interaction between dexamethasone and voriconazole and illustrates the time course of removal of the dexamethasone and the effect on voriconazole concentrations.