Aztreonam: The Monobactam Antibiotic for Gram-Negative Infections – Mechanism, Uses, and Safety

Monobactam antibiotic Aztreonam is used for Gram-negative infections. Learn its mechanism, spectrum, uses, contraindications, side effects, and monitoring.

Aztreonam: A Monobactam Antibiotic

Aztreonam is a monobactam antibiotic used for Gram-negative infections. It’s the only available drug in this class and is ideal for patients allergic to penicillin.

Medications in the Class

• Aztreonam (only available monobactam)

Mechanism of Action

Aztreonam binds to penicillin-binding protein 3 (PBP-3) in Gram-negative bacteria. This action stops cell wall synthesis, leading to bacterial death. It is bactericidal.

Spectrum of Activity

• Active against: Aerobic Gram-negative bacteria, including Enterobacteriaceae (E. coli, Klebsiella, Proteus, Enterobacter) and Pseudomonas aeruginosa.

• Not active against: Gram-positive bacteria or anaerobes.

Key Feature: Aztreonam is safe for patients with severe penicillin allergies, as it doesn't cross-react with other beta-lactams, except ceftazidime.

Indications (When Used)

• Severe Gram-negative infections in penicillin-allergic patients

• Complicated urinary tract infections

• Intra-abdominal infections (with metronidazole)

• Sepsis and bacteremia from Gram-negative bacteria

• Hospital-acquired pneumonia from susceptible Gram-negative pathogens

Contraindications (When Not to Use)

• Known hypersensitivity to aztreonam

• Ineffective against Gram-positive or anaerobic infections (should not be used alone if these are suspected)

Side Effects

• Gastrointestinal upset (nausea, vomiting, diarrhea)

• Rash and hypersensitivity reactions (rare compared to other beta-lactams)

• Elevated liver enzymes

• Phlebitis at the IV site

• Rare: hematologic issues (thrombocytopenia, eosinophilia)

Drug Interactions

• Aminoglycosides: Can be used together but may increase nephrotoxicity.

• Cephalosporins (Ceftazidime): Possible cross-reactivity due to similar side chains.

• No major cytochrome P450 interactions.

Antidote

There’s no specific antidote. Supportive treatment is given for overdose. Allergic reactions require epinephrine and antihistamines.

Monitoring Potential Complications

• Monitor renal function; dosage adjustments are needed in renal impairment.

• Watch for allergic reactions, especially in patients allergic to ceftazidime.

• Liver function tests during long-term use.

• Monitor for superinfections with extended use.

Aztreonam is vital for patients with severe beta-lactam allergies. It effectively targets aerobic Gram-negative bacteria, including Pseudomonas. However, it must be paired with other agents if Gram-positive or anaerobic organisms are suspected.