Risk of Nephrotoxicity Associated With Nonrenally Adjusted Intravenous Polymyxin B Compared to Traditional Dosing

Background: Polymyxin B's package insert recommends renal adjustment. Contemporary studies suggest it does not require renal adjustment. Objective: To determine whether time to acute kidney injury (AKI) differs between renally adjusted and nonadjusted intravenous (IV) polymyxin B. Methods: This retrospective chart review compared time to AKI after renally adjusted and nonadjusted IV polymyxin B administration. It included patients who were 18 years or older, received IV polymyxin B, and had creatinine clearance below 80 mL/min, and excluded ones who had AKI, received renal replacement therapy, or were pregnant. Results: Fifty-four patients were included. There was not any statistical association between dosing type and time to AKI (P = .13). Incidence of nephrotoxicity, mortality, and length of stay (LOS) were higher in the renally adjusted arm (21.7% vs 6.5%, 17.4% vs 6.5%, and 16 vs 14 days, respectively). Four patients received concomitant ascorbic acid; not one developed AKI. Conclusion: A significant association between IV polymyxin B dosing type and time to AKI was not found. Adverse events were higher in the renally adjusted arm. This suggests that nonadjusted IV polymyxin B may be preferred in patients with renal impairment. Ascorbic acid may mitigate IV polymyxin B's nephrotoxic potential. Further studies are needed to corroborate these findings.