Purpose: The role of colistin in the treatment of infections caused by multidrug-resistant gram-negative microorganisms is discussed.
Summary: Colistin is structurally and pharmacologically related to polymyxin B, the other commercially available drug from the polymyxin class. Colistin is bactericidal in nearly all strains of gram-negative bacilli. As with all antibiotics, resistance is of paramount concern. Resistance to colistin has not been frequently documented. Colistin must be administered parenterally, as it is not absorbed from the gastrointestinal tract, mucous membranes, or intact or denuded skin. Parenteral colistin has been replaced by less-toxic antibiotics and should be reserved for life-threatening infections caused by organisms resistant to preferred drugs. A number of published studies and case reports have reevaluated the safety and efficacy of parenteral colistin use in patients with multidrug-resistant infections. In three case series, 58-74% of patients exhibited a clinical response to colistin. Although colistin was previously viewed as reasonably effective but highly nephrotoxic, recent studies have suggested that nephrotoxicity may not be as severe as once thought. Frequent renal function monitoring is necessary in patients receiving colistin, since adverse renal effect may occur, regardless of the dosage given. The recommended dosage of parenteral colistin for adults and children with normal renal function is 2.5-5 mg/kg/day, administered as two to four divided doses. Doses must be adjusted for renal impairment, and dosing recommendations for patients undergoing renal replacement therapy have not been well established.
Conclusion: With vigilant monitoring of renal function and the avoidance of concomitant neurotoxic medications, colistin can be used safely and effectively with minimal adverse outcomes.