UC San Diego

Background. There are limited data on the impact of azole antifungal use on the appropriate dose conversion strategy from immediate-release tacrolimus (IR-Tac) to once-daily extended-release tacrolimus (LCP-Tacro tablets [LCPT]). The purpose of this study was to determine whether the initial IR-Tac–to-LCPT conversion ratio is affected by azole antifungal use. Methods. This single-center, retrospective cohort study included adult non–kidney transplant recipients who were converted from IR-Tac to LCPT between 2015 and 2022. Patients were grouped by azole antifungal use. The primary outcome was the IR-Tac–to-LCPT conversion ratio for those at goal tacrolimus trough, stratified by azole antifungal use. Secondary outcomes included conversion indications, acute kidney injury, neurological adverse effects, and rejection. Results. A total of 113 transplant recipients were included (liver 23 [20.4%], heart 70 [61.9%], lung 9 [8.0%], and multiorgan 11 [9.8%]). Twenty-two patients (19.5%) were on azole antifungals. A larger proportion of lung transplant recipients were on azole therapy compared with non–lung allograft recipients (27.3% versus 3.3%, P = 0.004). Conversion ratios were significantly higher for patients on azoles at 7 d ( P = 0.031), 30 d ( P = 0.038), and 90 d ( P = 0.001). Azole use was associated with lower LCPT doses at 7 d. There was no difference in patients at goal concentration or in the incidence of acute kidney injury between cohorts. Neurologic adverse effects related to IR-Tac prompted conversion in 55 patients, with 79.3% reporting improvement on LCPT. Conclusions. LCPT may be safely used in non–kidney transplant recipients regardless of azole antifungal use. Patients converting from IR-Tac to LCPT taking azole antifungals may warrant a higher dose conversion ratio, closer to 1, to achieve comparable tacrolimus trough concentrations.