Aztreonam
**Aztreonam** is a monobactam injectable antibiotic primarily utilized for its strong activity against a variety of aerobic and facultative gram-negative bacteria. * **Spectrum of Activity:** Highly effective against *Citrobacter*, *Enterobacter*, *E. coli*, *Klebsiella*, *Proteus*, *Pseudomonas*, and *Serratia*. * **Clinical Pearl:** It is **not** clinically efficacious against gram-positive or anaerobic bacteria. * **Clinical Utility:** Often considered for serious gram-negative infections when traditional choices like aminoglycosides or fluoroquinolones are ineffective or relatively contraindicated (e.g., due to nephrotoxicity concerns). * Exhibits excellent tissue penetration and generally has a low toxic potential, though clinical experience and pharmacokinetic data in veterinary target species remain limited.
Mechanism: Aztreonam is a **bactericidal** antibiotic. * It selectively binds to **penicillin-binding protein-3 (PBP-3)** in susceptible bacteria. * Binding to PBP-3 → **inhibits bacterial cell wall synthesis** → results in cell lysis and death. * It is highly stable against the hydrolytic effects of bacterial **beta-lactamases** and, unlike many other beta-lactam antibiotics, does not induce beta-lactamase activity. * **Synergy:** Can exhibit synergistic effects against *Pseudomonas aeruginosa* and other gram-negative bacilli when used concurrently with aminoglycosides.
Dosing by species
- Serious gram-negative infections · 30 mg/kg · IM or IV · q6-8h · Anecdotal dosing suggestion based on the human pediatric dose. Aztreonam has a shorter half-life in dogs but is about half as bound to plasma proteins compared to humans.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Documented severe hypersensitivity to aztreonam
Adverse effects
- Hypersensitivity reactions
- Gastrointestinal effects (bacterial overgrowth, pseudomembranous colitis, diarrhea)
- Pain and/or swelling after IM injection
- Phlebitis after IV administration
- Transient increases in liver enzymes, serum creatinine, and coagulation indices
Drug interactions
- Probenecid · Can reduce the renal tubular secretion of aztreonam, thereby maintaining higher systemic levels for a longer period of time. This potential 'beneficial' interaction requires further investigation in veterinary patients.
Monitoring
- Clinical efficacy
- Signs of toxicity or adverse effects
- Renal and hepatic function in compromised patients
Overdose
There is little reason for concern in patients with adequate renal function. The IV LD50 for mice is 3.3 g/kg. Hemodialysis or peritoneal dialysis may be used to clear aztreonam from the circulation.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.