Evaluation of the tacrolimus drug interaction with voriconazole vs clotrimazole in heart transplant recipients

Antifungal prophylaxis postheart transplant (HT) may include voriconazole or clotrimazole, which interact with tacrolimus. There is no guidance for tacrolimus adjustment when transitioning from voriconazole to clotrimazole; therefore, this study evaluates tacrolimus concentration/dose (C/D) ratio on voriconazole compared to clotrimazole. This retrospective, single-center analysis included HT recipients (February 2016-September 2021) who received tacrolimus and voriconazole followed by clotrimazole. Tacrolimus C/D ratio was compared on voriconazole vs clotrimazole, and on clotrimazole vs postantifungal discontinuation. Seventy-two patients were included. The median (interquartile range) tacrolimus C/D ratio was 41% (1.7-fold) lower after transition from voriconazole to clotrimazole [5.1 (3.5, 7.7) vs 3.0 (2.0, 4.6) (ng/ml)/(mg/day), p p = 0.1]. These data indicate that a 70% tacrolimus dose increase may be appropriate when transitioning from voriconazole to clotrimazole in HT recipients.