Introduction: Polymyxins are used as the “last-line therapy” for multi drug resistant (MDR) Gram-negative bacterial infections. However, the development of nephrotoxicity is a major concern. The objectives of this study were to determine the incidence and severity of acute kidney injury (AKI) and to identify risk factors associated with AKI and mortality rate in Malaysian patients on polymyxin B (PMB) for MDR Gram-negative bacterial infections. Methods: A retrospective study was conducted in Universiti Kebangsaan Malaysia Medical Centre (UKMMC). Medical and
medication charts were reviewed for all intensive care unit (ICU) patients who received intravenous (IV) PMB from 1st May 2008 to 1st May 2018. Simple and multiple logistic regression were performed to identify risk factors of PMB induced nephrotoxicity. Results: Among the total 572 patients identified, only 31 patients were eligible to be included. The incidence rate of AKI was 45.2% (14 of 31 patients). Univariate analysis showed that age was a significant risk factor of PMB associated nephrotoxicity [OR 1.074; 95% CI 1.002-1.151; P=0.045]. Other four variables (P