2006 Volume 29 Issue 12 Pages 2528-2531
The purpose of this study was to assess the impact by switching co-administered triazole antifungal agent from fluconazole (FCZ) to voriconazole (VCZ) on the blood concentration of tacrolimus (FK506) in patients receiving allogeneic hematopoietic stem cell transplantation. We performed a retrospective study presented as case reports. The blood concentration of FK506 was increased after the switch from FCZ to VCZ, resulting in increase of the concentration/dose (C/D) ratio of FK506. Thus, the mean C/D ratios of FK506 with oral administration was surprisingly increased over 4.5-fold after the switch. Therefore, it was necessary to reduce the FK506 dose when co-administered FCZ is switched to VCZ. We should be careful when interpreting the results of these case reports; however, in some patients, it is recommended that the dose of FK506 be reduced to one-fifth after the switch.