Voriconazole-induced visual abnormality based on drug interaction between voriconazole and esomeprazole: A case report

We report a case of voriconazole-induced visual abnormality based on drug interaction of voriconazole and esomeprazole, therapeutic drug monitoring, and optimal therapy. An 81-year-old male developed visual abnormality after the blood concentration of voriconazole was up to 6.47 mg/L induced by coadministration with esomeprazole. Voriconazole is a substrate of multiple CYP450 isoenzymes including CYP2C19 (the major route), CYP3A4, and CYP2C9. Esomeprazole, a proton pump inhibitor (PPI), is also converted to inactive metabolites through CYP3A4 and CYP2C19-mediated metabolism, and is also a CYP2C19 inhibitor. The coadministration with esomeprazole inhibited the metabolism of voriconazole via CYP2C19 and promoted the elevation of voriconazole blood concentration beyond the minimum toxic level (5.5 mg/L). According to the pharmacist's advice, the adverse effects of visual abnormalities in the patient disappeared after the clinician reduced voriconazole dosage by 50% when other medication schedules remained unchanged. Therefore, therapeutic drug monitoring of voriconazole should be considered in patients receiving PPIs, especially esomeprazole, in order to adjust the dosage in time and achieve optimal therapeutic response and minimal adverse reaction.