Effect of Voriconazole on Tacrolimus Blood Concentration in Renal Transplant Recipients after Voriconazole Discontinuation

What is Known and Objective. Voriconazole (VRC) increases the blood concentration of Tacrolimus (TAC). However, the patterns of changes in TAC trough concentration (TAC C0) and dose-adjustment regimens after VRC discontinuation have not been reported. We aimed to explore the changing pattern of TAC C0 after VRC discontinuation and provide strategies for TAC dose adjustment and blood concentration monitoring in renal transplant recipients. Methods. The clinical data of 46 renal transplant patients pre- and during VRC medication and VRC discontinuation were retrospectively recorded, including doses and concentrations ₀ of TAC and VRC; biochemical indicators such as liver and kidney function; and CYP3A5, CYP3A4, and CYP2C19 gene types. Results and Discussion. After discontinuing VRC for 2–4 days, 81% of the patients returned to their initial TAC dose, although TAC C₀ and TAC dose-adjusted trough concentration (C/D) were 2.43-fold and 3.35-fold higher, respectively, than pre-VRC administration. After 5–7 days, TAC C₀ and C/D gradually recovered. TAC C/D was significantly higher after VRC discontinuation when the VRC trough concentration (VRC C0) was greater than 2.43 mg/L; CYP3A5, CYP3A4, and CYP2C19 genotypes and the administration of erythromycin did not affect the change in TAC C/D. What is New and Conclusion. TAC C/D remains elevated 2–4 days after discontinuing VRC compared to pre-VRC administration, with gradual recovery observed 5–7 days after VRC discontinuation. To avoid excessive blood TAC C0 , the initial TAC dose should not be immediately reinstated upon VRC discontinuation for 2–4 days. VRC C₀ are a critical factor influencing the change in TAC C/D ratio after VRC discontinuation.