Effects of Isavuconazole on the Plasma Concentrations of Tacrolimus among Solid-Organ Transplant Patients

We evaluated the interaction between isavuconazole and tacrolimus among 55 organ transplant recipients. After isavuconazole discontinuation, the tacrolimus concentration/dose ratio normalized by weight (C/D) was reduced by 16%. Liver transplant recipients experienced the largest C/D reduction. A 1.3-fold decrease in tacrolimus daily dose was required to maintain desired tacrolimus levels. There was considerable interpatient variability in the magnitude of the drug interaction. Tacrolimus doses should not be adjusted uniformly but, rather, be guided by therapeutic drug monitoring.