Comparison of nephrotoxicity of Colistin with Polymyxin B administered in currently recommended doses: a prospective study

BACKGROUND: The most important concern with polymyxins (Colistin and Polymyxin B) use is nephrotoxicity. There is no prospective data comparing nephrotoxicity of these two drugs, when administered in high doses and as per current recommendations. We conducted a prospective study to compare their trend of nephrotoxicity in our patient population. METHODS: Our study included adult ICU patients who received more than 48 h of Colistin or Polymyxin B and had no confounding factors for nephrotoxicity. Loading and maintenance doses were given as per a uniform protocol. Nephrotoxicity was defined as twofold increase in serum creatinine, or 50% decrease in estimated baseline creatinine clearance. Patients were followed up for 1 week after therapy. Statistical analysis was performed using SPSS version 20.0. RESULTS: 61 patients were included in Colistin group, and 51 patients in Polymyxin B group. Median Colistin dose was 233.3 (IQR 150-300) mg/day and median Polymyxin B dose was 200 (IQR 180-240) mg/day. Median duration of Colistin and Polymyxin B use was 7 (IQR 5-7) days and 7 (IQR 7-9) days respectively. Nephrotoxicity developed in 39.3% patients in Colistin group compared to 11.8% patients in Polymyxin B group. Mean onset of nephrotoxicity was 3.8 ± 0.8 days with Colistin, and 4.2 ± 0.7 days with Polymyxin B therapy. In bivariate analysis, Colistin daily dose ≥ 300 mg was found to be associated with nephrotoxicity. There was no effect of age or BMI on Colistin toxicity. Mean duration of renal failure was 4.9 ± 3.1 days with Colistin use, and 5.0 ± 2.4 days with Polymyxin B use. 75% patients in Colistin group and 83.3% patients in Polymyxin B group who developed nephrotoxicity recovered their renal function by 1 week. CONCLUSIONS: Colistin in currently recommended doses is significantly more nephrotoxic than Polymyxin B. Colistin toxicity is dose-dependent, mostly mild to moderate, and is reversible in most cases.