Za Pharmacy
Drugs, Supplies and Delivery
Aztreonam
Aztreonam is a unique monobactam antibiotic with a narrow spectrum of activity, primarily targeting Gram-negative bacteria. It is particularly valuable for treating infections in patients with beta-lactam allergies, as it lacks cross-reactivity with penicillins and cephalosporins. This article references the British National Formulary (BNF), Lippincott Textbook of Pharmacology, and Lange Basic & Clinical Pharmacology to provide a detailed overview of aztreonam, covering its mechanism of action, uses, dosage, side effects, precautions, drug interactions, and generic names.
Aztreonam exerts its bactericidal effect by inhibiting bacterial cell wall synthesis. According to the Lippincott Textbook of Pharmacology, aztreonam binds to penicillin-binding protein 3 (PBP-3) on the bacterial cell wall, disrupting peptidoglycan cross-linking. This weakens the cell wall, leading to osmotic instability and cell lysis.
The Lange Basic & Clinical Pharmacology highlights aztreonam’s resistance to many beta-lactamases, including ESBLs (extended-spectrum beta-lactamases). However, it is inactive against Gram-positive bacteria and anaerobes, making it a targeted therapy for Gram-negative infections.
Aztreonam is indicated for the treatment of:
- Gram-Negative Bacterial Infections:
- Respiratory Tract Infections: Pneumonia (hospital-acquired and ventilator-associated).
- Urinary Tract Infections (UTIs): Complicated pyelonephritis, cystitis.
- Intra-Abdominal Infections: Peritonitis, biliary tract infections.
- Skin and Soft Tissue Infections: Cellulitis, wound infections.
- Septicemia: Bloodstream infections.
- Cystic Fibrosis: Inhaled aztreonam (not discussed here) for chronic Pseudomonas aeruginosa infections.
The BNF emphasizes its role as a safe alternative for patients with beta-lactam allergies, as it does not cross-react with penicillins or cephalosporins.
Dosing varies by infection severity, patient age, and renal function:
Adults and Children (>12 years):
- Moderate Infections: 1 g IV/IM every 8–12 hours.
- Severe Infections (e.g., septicemia): 2 g IV every 6–8 hours.
Children (<12 years):
- Moderate Infections: 30 mg/kg IV/IM every 6–8 hours (max 120 mg/kg/day).
- Severe Infections: 50 mg/kg IV every 6–8 hours (max 8 g/day).
Renal Impairment:
- Creatinine Clearance (CrCl) 10–30 mL/min: Reduce dose by 50%.
- CrCl <10 mL/min: Reduce dose by 75%.
Administration Tips:
- IV Infusion: Dilute in 50–100 mL of compatible fluid (e.g., 0.9% saline) and infuse over 20–60 minutes.
- IM Injection: Reconstitute with sterile water to reduce pain.
Aztreonam is generally well-tolerated, but potential side effects include:
- Common:
- Gastrointestinal disturbances (nausea, vomiting, diarrhea).
- Injection site reactions (pain, redness, swelling).
- Rash or pruritus.
- Serious (Rare):
- Hypersensitivity reactions (anaphylaxis, angioedema).
- Clostridioides difficile-associated diarrhea (CDAD).
- Hematologic effects (thrombocytopenia, neutropenia).
- Seizures (with high doses in renal impairment).
- Contraindications: Hypersensitivity to aztreonam or other monobactams.
- Renal Impairment: Dose adjustment is critical to avoid toxicity.
- Pregnancy and Lactation: Generally safe but use only if benefits outweigh risks.
- Pediatric Use: Safe for children, but dosing must be weight-based.
- Cross-Reactivity: No cross-reactivity with penicillins or cephalosporins, making it safe for patients with beta-lactam allergies.
Key interactions per the BNF and Lange Basic & Clinical Pharmacology:
- Aminoglycosides: Synergistic against Gram-negative bacteria but may increase nephrotoxicity.
- Probenecid: Reduces renal excretion, increasing aztreonam levels (avoid concurrent use).
- Oral Anticoagulants (e.g., warfarin): Enhanced anticoagulant effect (monitor INR).
- Cefoxitin and Imipenem: Antagonistic effect; avoid concurrent use.
- Generic: Aztreonam.
- Brand Names: Azactam®, Cayston® (inhaled form).
