Contribution of voriconazole N‐oxide plasma concentration measurements to voriconazole therapeutic drug monitoring in patients with invasive fungal infection
Christelle Boglione‐Kerrien, Jeff Morçet, Lucie‐Marie Scailteux, François Bénézit, Christophe Camus, Jean-Baptiste Méar, Jean‐Pierre Gangneux, Éric Bellissant, Camille Tron, Marie‐Clémence Verdier, F. Lemaı̂tre
Abstract
Abstract Background Voriconazole (VRC), a widely used triazole antifungal, exhibits significant inter‐ and intra‐individual pharmacokinetic variability. The main metabolite voriconazole N‐oxide (NOX) can provide information on the patient's drug metabolism capacity. Objectives Our objectives were to implement routine measurement of NOX concentrations and to describe the metabolic ratio (MR), and the contribution of the MR to VRC therapeutic drug monitoring (TDM) by proposing a suggested dosage‐adjustment algorithm. Patients and Methods Sixty‐one patients treated with VRC were prospectively included in the study, and VRC and NOX levels were assayed by LC–MS/MS. A mixed logistic model on repeated measures was implemented to analyse risk factors for the patient's concentration to be outside the therapeutic range. Results Based on 225 measurements, the median and interquartile range were 2.4 μg/ml (1.2; 4.2), 2.1 μg/ml (1.5; 3.0) and 1.0 (0.6; 1.9) for VRC, NOX and the MR, respectively. VRC C min <2 μg/ml were associated with a higher MR during the previous visit. MR values >1.15 and <0.48 were determined to be the best predictors for having a VRC C min lower than 2 μg/ml and above 5.5 μg/ml, respectively, at the next visit. Conclusions Measurement of NOX resulted useful for TDM of patients treated with VRC. The MR using NOX informed interpretation and clinical decision‐making and is very interesting for complex patients. VRC phenotyping based on the MR is now performed routinely in our institution. A dosing algorithm has been suggested from these results.