Polymyxins have significant toxicity on parenteral administration. Nephrotoxicity is observed often (30-60%) because tubular reabsorption concentrates colistin and polymyxin B in the kidneys and generates toxic concentrations of polymyxins. The toxicity can be partially mitigated by coadministration of antioxidants. Neurotoxicity (with paresthesia, nausea and vomiting, neuropathy, or other sequelae) is observed in nearly 7% of patients. Extended exposure or conditions such as myasthenia gravis or renal dysfunction predispose to neurotoxicity. Skin hyperpigmentation and lung toxicity (for inhaled colistin or polymyxin B) are also observed.