Polymyxin B
Overview
Polymyxin B is a cyclic lipopeptide antibiotic derived from Bacillus polymyxa, consisting of a heptapeptide ring and a tripeptide side chain acylated with a fatty acid tail. The molecule binds to lipopolysaccharide in the outer membrane of Gram-negative bacteria, causing membrane permeabilization and cell death. Its cationic residues interact electrostatically with anionic phosphate groups on lipid A. Polymyxin B is reserved for serious infections caused by multidrug-resistant Gram-negative pathogens when other options are unavailable.
Key Research Findings
Polymyxin B received FDA approval in the 1960s and remains in clinical use for severe infections caused by carbapenem-resistant Enterobacteriaceae and Acinetobacter species. Nephrotoxicity and neurotoxicity limit its use, prompting development of dosing protocols based on therapeutic drug monitoring. Recent pharmacokinetic studies have refined dosing strategies to optimize efficacy while minimizing adverse renal effects.
Intravenous, Intrathecal, Topical
FDA Approved
Interested in Polymyxin B?
Find a verified provider experienced with Polymyxin B protocols in your area. All providers are credentialed and use compliant sourcing.
Find a Polymyxin B ProviderRelated Peptides
Enfuvirtide (Fuzeon)
FDA ApprovedA 36-amino acid synthetic peptide that inhibits HIV-1 entry into CD4+ T-cells by blocking the gp41-mediated membrane fusion step. Enfuvirtide binds to the first heptad repeat (HR1) region of gp41, preventing the conformational change required for viral-cell membrane fusion. It is the first and only FDA-approved fusion inhibitor and is active against HIV-1 strains resistant to other antiretroviral drug classes.
Magainin 2
Research PhaseMagainin 2 is a 23-amino acid antimicrobial peptide originally isolated from the skin of the African clawed frog Xenopus laevis. It exerts broad-spectrum antimicrobial activity through membrane disruption, forming pores in bacterial membranes while exhibiting relative selectivity over mammalian cells. Magainin 2 belongs to the alpha-helical cationic antimicrobial peptide family and has served as a template for numerous synthetic analogs. Its mechanism of action, which is distinct from conventional antibiotics, offers potential against multidrug-resistant pathogens.
Pexiganan (MSI-78)
In Clinical TrialsPexiganan is a 22-amino acid synthetic analog of magainin 2 designed to enhance antimicrobial potency and proteolytic stability. It disrupts bacterial membranes through electrostatic interaction and pore formation, demonstrating broad-spectrum activity against gram-positive and gram-negative organisms, including methicillin-resistant Staphylococcus aureus. Pexiganan was developed as a topical agent for infected diabetic foot ulcers, leveraging its rapid bactericidal action and low resistance potential. Structural modifications from the parent magainin sequence improve its pharmacological profile for clinical use.
Omiganan
In Clinical TrialsOmiganan is a synthetic 12-amino acid cationic antimicrobial peptide derived from indolicidin, a naturally occurring peptide from bovine neutrophils. It acts by disrupting microbial membranes and demonstrates activity against bacteria, fungi, and some viruses. Omiganan was developed as a topical agent to prevent catheter-related bloodstream infections through its broad-spectrum antimicrobial properties. Its small size and potent activity made it a candidate for preventing biofilm formation on medical devices.