Medicine & USMLE

Monobactams (Aztreonam)

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


Monobactams are a class of antibiotics used to treat gram negative bacterial infections. One important monobactam to know is Aztreonam. 

Like penicillins, these drugs are beta-lactam antibiotics; they are D-Ala-D-Ala analogs that bind to and block the bacterial transpeptidase, thereby preventing the cross-linking of the bacterial cell wall. Monobactams are also resistant to penicillinase, a bacterial enzyme that can deactivate penicillins by cleaving the beta-lactam ring. 

These drugs are only active against gram-negative rods. Because there is no cross-allergenicity between monobactams and penicillin, monobactams are often used in patients with penicillin allergies.

Key Points

  • Monobactams
    • Drug Names
      • Aztreonam
    • Mechanism
      • Beta-lactam antibiotic
        • Prevents peptidoglycan cross-linking by binding to penicillin-binding protein 3 (PBP3)
        • Similar mechanism to penicillin, but different chemical structure
      • Synergistic with aminoglycosides
    • Clinical Use
      • Gram-negative rods only
        • No activity against gram-positive rods or anaerobes
      • For penicillin-allergic patients and those with renal insufficiency who cannot tolerate aminoglycosides
    • Adverse Effects
      • No cross-allergenicity with penicillins
        • Used in patients who are allergic to penicillins without issues
      • Occasional GI upset
    • Resistance
      • Resistant against beta-lactamases (penicillinase)