Comparison between standard-release and extended-release tacrolimus in lung transplantation

<bold>Introduction:</bold> Two oral formulations of tacrolimus [twice-daily administered immediate-release (IR-TAC) and once-daily extended-release (XL-TAC)] are available in Switzerland. Their safety and efficacy has not been adequately compared in lung transplantation (LT). <bold>Methods:</bold> We retrospectively assessed adult LT recipients (2008-2022) who underwent conversion from IR-TAC to XL-TAC. We analysed the changes over time in the slope of the forced expiratory volume in 1 second (FEV₁) and estimated glomerular filtration rate (eGFR) and evaluated tacrolimus trough level stability using a random effects logistic regression model. <bold>Results:</bold> Sixty-two patients were included in the study. The conversion took place 759 (SD 812) days after LT. Although we observed a statistically significant decrease in the slope of FEV1 (p=0.0061) following conversion, this cannot be directly attributed to the switch as it is consistent with the usual course of lung function after LT (initial peak during the first year followed by a gradual decline, often due to chronic lung allograft dysfunction). The introduction of XL-TAC was associated with a decrease of the rate of decline of eGFR (p=0.0105). Tacrolimus trough levels were on-target in 38% of patients while on IR-TAC and 40% on XL-TAC (p=0.392). <bold>Conclusion:</bold> The conversion of IR-TAC to XL-TAC was associated with a decrease of nephrotoxicity but did not result in an increase of on-target tacrolimus trough levels. The observed decline in lung function, albeit significant, likely corresponds to the natural course of graft function after LT. Further prospective studies are required to investigate the impact of XL-TAC on lung function and graft survival.