Acute kidney injury with intravenous colistin sulfate compared with polymyxin B in critically ill patients: A real‐world, retrospective cohort study

Abstract Background Polymyxins have re‐emerged as a last‐resort therapeutic option for infections caused by carbapenem‐resistant gram‐negative bacteria. Nephrotoxicity induced by polymyxins is a significant limitation of its use in the clinic. Polymyxin B and colistin sulfate are two widely used active formulations of polymyxins. However, there is a lack of studies conducting a comparative assessment of nephrotoxicity between the two formulations. This study aimed to compare the nephrotoxicity of polymyxin B and colistin sulfate in critically ill patients. Methods We conducted a retrospective cohort study among critically ill patients who received intravenous polymyxin B or colistin sulfate for over 48 h from January 2017 to January 2024. The primary outcome was the incidence of acute kidney injury (AKI) associated with polymyxins, and the secondary outcome was 30‐day all‐cause mortality. Additionally, the risk factors of polymyxins‐induced AKI and 30‐day all‐cause mortality were identified by Cox proportional hazard regression analysis. Results A total of 473 patients were included in this study. The overall incidence of AKI was significantly higher in patients who received polymyxin B compared to those who received colistin sulfate in the unmatched cohort (20.8% vs. 9.0%, p = 0.002) and in the propensity score matching cohort (21.1% vs. 7.0%, p = 0.004), respectively. However, there was no significant difference in 30‐day all‐cause mortality between the two groups. Polymyxin type, septic shock, and concomitant use of vasopressors were identified as independent risk factors for polymyxin‐induced AKI. Conclusions The prevalence of AKI was higher among patients who received polymyxin B compared to those treated with colistin sulfate. However, there was no significant difference in 30‐day all‐cause mortality between the two groups. Further prospective, multicenter studies with larger sample sizes are needed to validate these findings.