Colistin (CS) is a polymyxin with bactericidal activity, which is increasingly used in nosocomial infections associated with multidrug-resistant Gram-negative bacteria (MDR-GNB). Intravenous CS is usually administered as a less toxic pro-drug, i.e. colistin sodium methanesulfonate (CMS). In water-containing solutions, CMS undergoes a spontaneous hydrolysis to form a complex mixture of partially sulfomethylated derivatives and CS. Pharmacokinetic of CS is dependent on the route of administration, i.e. parenteral, intramuscular, nebulized, intrathecal/intraventricular. Renal toxicity is the most common adverse effect of CS treatment, as the drug is excreted primarily by the kidney and elevated levels of CS may further impair renal function, with a dose-dependent effect. Clinical manifestations of CS associated nephrotoxicity include acute kidney injury, proteinuria and tubular damage. Only few data are currently available on the effects of different renal replacement therapy modalities on CS pharmacokinetics. In patients undergoing the most efficient forms of renal replacement therapies, the extracorporeal clearance of CMS may result in a substantial removal of the antibiotic. Thus, in this setting, the recommended daily doses should be increased. Future studies should better explore CS pharmacokinetics in patients undergoing different modalities of renal replacement therapy.