 Colistin, also known as polymixin E, is a peptide antibiotic that demonstrates concentration-dependent bactericidal killing against gram-negative pathogens including Pseudomonas and Acinetobacter. Originally discovered in the 1950s, its use has been limited due to the concern for its systemic toxicities including nephrotoxicity and neurotoxicity. However, a revival of colistin use has been seen in recent years due to the increased emergence of multidrug-resistant MDR gram-negative pathogens and a lack of alternative antimicrobial therapies. 