NCI Drug Dictionary

The NCI Drug Dictionary contains technical definitions and synonyms for drugs/agents used to treat patients with cancer or conditions related to cancer. Each drug entry includes links to check for clinical trials listed in NCI's List of Cancer Clinical Trials.

polymyxin B
A mixture of the polypeptides polymyxins B1 and B2, both obtained from Bacillus polymyxa strains, with antimicrobial activity. Polymyxin B exerts its antimicrobial effect through its cationic detergent action on cell membranes. Specifically, this antibiotic binds to the negatively charged site in the lipopolysaccharide layer of the bacterial cell membrane via electrostatic affinity with the positively charged amino groups in the cyclic peptide portion. Subsequently, the fatty acid portion of polymyxin B dissolves in the hydrophobic region of the bacterial cell membrane. This results in an alteration in cell membrane structure, disruption of cell wall integrity and an increase in permeability for water and molecules. This will eventually lead to bacterial cell death. Check for active clinical trials using this agent. (NCI Thesaurus)