Risk factors for acute kidney injury in patients treated with polymyxin B or colistin methanesulfonate sodium

Polymyxin B (PMB) and colistin, administered as the prodrug colistin methanesulfonate sodium (CMS), are increasingly used to treat carbapenem-resistant Gram-negative bacteria. Nephrotoxicity is the major dose-limiting adverse effect of both polymyxins. A retrospective cohort study of 132 patients was conducted to evaluate risk factors for acute kidney injury (AKI), classified according to Acute Kidney Injury Network criteria, in patients treated with >= 48 h of intravenous PMB or CMS, with particular focus on potential differences between each polymyxin. The overall incidence of AKI was 25.8% (341132) [20.8% (20196) and 38.9% (14136) in patients treated with PMB and CMS, respectively; P=0.06]. In the Cox regression model, doses >= 2 million International Units (MIU) of PMB or >9 MIU of CMS were the only variable independently associated with AKI [adjusted hazard ratio (aHR) = 2.11, 95% confidence interval (CI) 1.01-4.41; P=0.04]. Vancomycin co-administration was strongly associated with AKI, although this was not statistically significant (aHR = 2.22, 95% CI 0.98-5.04; P=0.058). There was no statistically significant difference in the incidence of AKI between patients treated with PMB or CMS in the multivariate model (aHR = 1.74, 95% CI 0.82-3.69; P=0.15). High dose was the main risk factor for AKI regardless of the polymyxin administered. Vancomycin co-administration likely increases the risk of AKI. Although there was a higher overall incidence of AKI in patients treated with CMS compared with PMB, CMS was not significantly associated with this outcome after adjusting for the above variables. (C) 2013 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.