USMLE

Polymyxins

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Antibiotics / Antiparasitics
  1. Penicillin Overview
  2. Penicillinase-Sensitive vs. Penicillinase-Resistant Penicillins
  3. Anti-Pseudomonal Penicillins
  4. Cephalosporins Overview
  5. 1st Generation Cephalosporins
  6. 2nd Generation Cephalosporins
  7. 3rd Generation Cephalosporins
  8. 4th Generation Cephalosporins
  9. 5th Generation Cephalosporins
  10. Carbapenems
  11. Monobactams (Aztreonam)
  12. Vancomycin
  13. Aminoglycosides
  14. Tetracyclines
  15. Tigecycline
  16. Chloramphenicol
  17. Clindamycin
  18. Linezolid
  19. Macrolides
  20. Polymyxins
  21. Sulfonamides
  22. Dapsone
  23. Trimethoprim
  24. Fluoroquinolones
  25. Daptomycin
  26. Metronidazole
  27. Rifamycins (Rifampin, Rifabutin)
  28. Isoniazid
  29. Pyrazinamide
  30. Ethambutol
  31. Chloroquine

Summary

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