Voriconazole pseudotoxicity: a case report highlighting the importance of sampling timing in TDM interpretation by clinical pharmacists.

This case report describes a 57-year-old male patient who sought medical attention due to severe pneumonia and respiratory failure. The initial empirical antibiotic treatment was ineffective. Bronchoscopy and lung alveolar lavage fluid culture confirmed a case of Aspergillus fumigatus infection. Antifungal treatment with the conventional dose of VRZ was administered, but the patient continued to have a fever, and the trough concentration of VRZ detected exceeded the upper limit of the normal range. The clinical pharmacist discovered that the blood sample collected for TDM of this patient was taken 2 h after medication administration rather than the trough concentration. Based on the data of Aspergillus resistance monitoring network and the phenomenon that the patient's blood drug concentration did not match the clinical efficacy, the clinical pharmacist recommended increasing the dose of VRZ and suggested re-testing the trough concentration of VRZ after the blood drug concentration reached a steady state. The patient rapidly achieved a fever reduction and was ultimately cured. The re-tested blood drug concentration was within the normal range. This case demonstrates that clinical pharmacists play an indispensable role in the quality control of therapeutic drug monitoring. They will standardize the sampling time, interpret the test results in combination with the clinical condition, adjust the dose based on pharmacokinetic principles, strengthen interdisciplinary cooperation, and optimize antifungal treatment.