Colistin (polymyxin E) is a polymyxin antibiotic produced by certain strains of Bacillus polymyxa var. colistinus. Colistin is a mixture of cyclic polypeptides colistin A and B. Colistin is effective against Gram-negative bacilli, except Proteus.

Administration

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Colistin is used as a sulfate or as sulfomethylated form, colistimethate. Colistin sulfate tablets are used to treat intestinal infections, or to suppress colonic flora. Colistin sulfate is also used as topical creams, powders, and otic solutions. Colistimethate is used for parenteral administration, and also as an aerosol to treat pulmonary infections.

Mode of action

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Colistin is polycationic and has both hydrophilic and lipophilic moieties. These interact with the bacterial cytoplasmic membrane, changing its permeability. This effect is bactericidal.

Pharmacokinetics

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The absorption of colistin from the gastrointestinal tract is very poor. The main elimination route of colistin is through renal excretion.

Polymyxin antibiotics

Colistin