Aztreonam Dosage and Treatment Guidelines for Susceptible Gram-Negative Infections
The recommended dosage of aztreonam for infections caused by susceptible gram-negative bacteria is 1-2 grams intravenously every 6-8 hours for moderate to severe systemic infections, with treatment duration typically 7-14 days. 1, 2
Dosage Recommendations by Infection Severity
Aztreonam dosing should be adjusted based on the severity of infection:
- Urinary tract infections: 500 mg or 1 g IV/IM every 8-12 hours 2
- Moderately severe systemic infections: 1 g or 2 g IV/IM every 8-12 hours 2
- Severe systemic or life-threatening infections: 2 g IV every 6-8 hours 2
- Pseudomonas aeruginosa infections: 2 g IV every 6-8 hours is recommended at least upon initiation of therapy 2
Special Populations
Renal Impairment
- Creatinine clearance 10-30 mL/min: Half the usual dose after an initial loading dose of 1-2 g 2
- Creatinine clearance <10 mL/min: One-fourth of usual initial dose at the usual fixed interval 2
- Hemodialysis patients: One-eighth of initial dose should be given after each hemodialysis session in addition to maintenance doses 2
Pediatric Patients
- Mild to moderate infections: 30 mg/kg every 8 hours 2
- Moderate to severe infections: 30 mg/kg every 6-8 hours 2
- Maximum recommended dose: 120 mg/kg/day 2
Antimicrobial Spectrum and Clinical Applications
Aztreonam has a unique and targeted spectrum of activity:
- Highly effective against: Most Enterobacteriaceae, Pseudomonas aeruginosa, Haemophilus influenzae, and Serratia marcescens 1, 3
- No activity against: Gram-positive bacteria and anaerobes 3, 4
This makes aztreonam particularly valuable for:
- Patients with severe penicillin allergies as an alternative to β-lactam antibiotics (at 2 g IV every 8 hours) 1
- Treatment of aerobic gram-negative infections including:
- Complicated urinary tract infections
- Lower respiratory tract infections
- Intra-abdominal infections
- Septicemia
- Skin and soft tissue infections 5
Combination Therapy Considerations
- For mixed infections or those of unknown etiology, combination therapy is recommended to ensure coverage of gram-positive and anaerobic bacteria 5
- Aztreonam shows synergy with aminoglycosides against P. aeruginosa, Acinetobacter, and gentamicin-resistant gram-negative rods 3
- For metallo-β-lactamases-producing CRE infections, aztreonam should be used in combination with ceftazidime-avibactam 1
Treatment Duration
- Generally, aztreonam should be continued for at least 48 hours after the patient becomes asymptomatic or evidence of bacterial eradication has been obtained 2
- For most bacterial infections, treatment duration of 7-14 days is recommended 6, 1
- Persistent infections may require treatment for several weeks 2
Clinical Efficacy and Outcomes
Clinical studies have demonstrated high efficacy rates with aztreonam:
- 81.6% cure rate in difficult-to-treat infections after a 6-week post-treatment follow-up 7
- Effective in eradicating pseudomonal infections in most patients (except those with cystic fibrosis) 4
- 86% overall clinical response in patients with serious infections due to multiresistant gram-negative organisms 8
Important Caveats and Considerations
- Aztreonam should not be used as monotherapy for mixed infections due to its lack of activity against gram-positive and anaerobic bacteria 5
- When treating suspected Pseudomonas infections, the higher dosage (2 g every 6-8 hours) should be used initially 2
- For patients with beta-lactam allergies, remember that aztreonam has minimal cross-reactivity with other beta-lactams 1
- Serum drug levels of aztreonam exceed MIC90 values for most Enterobacteriaceae for 8 hours and for P. aeruginosa for almost 6 hours after a 2 g IV dose 3
By following these guidelines, clinicians can optimize the use of aztreonam for susceptible gram-negative infections while ensuring appropriate coverage for the targeted pathogens.