Monobactams (Aztreonam)

Summary

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)