Polymyxins are a class of antibiotics including the drug colistin. These drugs function by disrupting the membranes of bacteria, causing leakage of cellular components and bacterial cell death. Clinically, colistin and other polymyxins are used as last resort treatments in gram negative bacterial infections. They can cause a host of serious adverse effects, including nephrotoxicity, neurotoxicity and respiratory failure.

Key Points

  • Polymyxins
    • Drug Names
      • Colistin (polymyxin E)
        • Found in Thayer-Martin selective chocolate agar (used in laboratory settings to selectively culture Neisseria spp.)
      • Polymyxin B
    • Mechanism
      • Cation polypeptides that disrupts cell membrane
        • Causes leakage of cellular components and cell death
    • Clinical Use
      • Last-resort therapy for multidrug-resistant gram-negative bacteria
        • e.g. P. aeruginosa, E. coli, K. pneumoniae
      • Found in antibiotic ointments for superficial skin infections
    • Adverse Effects
      • Nephrotoxicity
      • Neurotoxicity
        • Includes slurred speech, weakness, paresthesias
      • Respiratory failure