Monobactams (Aztreonam)



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)