Polymyxin

Polymyxins are a group of polypeptide antibiotics that branched chemically representing cyclic decapeptides (peptides of 10 amino acids ). Similar to the cell membrane, they have a polarity which is formed by the amino acids contained in them, and terminal hydrophobic fatty acids. Thereby they can be stored in the cell membrane of Gram-negative bacteria and interfere with their permeability. Because of these antibiotics have a bactericidal effect, but only against outside the body cells ( extracellular) localized germs. The polymyxins include polymyxin B and colistin.

For parenteral application polymyxins exert very high toxicity, especially on the nervous system ( neurotoxicity) and the kidney ( nephrotoxicity ). In renal failure, they are absolutely contraindicated. Therefore, they are applied topically particularly Colistin is used in veterinary medicine as well as systemically. In the intestine, they are not absorbed.