Therapeutic drug monitoring
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Although voriconazole (VRCZ) is metabolized to VRCZ N-oxide principally by CYP2C19, VRCZ clearance is affected by multiple factors. In this study, we investigated the relationship between the CYP2C19 phenotype using the VRCZ-to-VRCZ N-oxide plasma concentration ratio (VRCZ/N-oxide) and demographic and clinical characteristics of Japanese patients taking VRCZ. ⋯ It is possible to comprehensively evaluate CYP2C19 activity using the actual measured value of the VRCZ/N-oxide ratio in patients taking VRCZ. The predictive performance of the VRCZ/N-oxide ratio was improved by including the route of administration, C-reactive protein level, and patient age in addition to the CYP2C19 genotype as predictive factors.