Aztreonam Dosing for Adults with Normal Renal Function
For adults with normal renal function, aztreonam should be dosed at 1-2 grams every 8 hours for moderately severe systemic infections, or 2 grams every 6-8 hours for severe systemic or life-threatening infections, with a maximum daily dose of 8 grams. 1
Standard Dosing by Infection Severity
The FDA-approved dosing regimen varies based on infection type and severity 1:
- Urinary tract infections: 500 mg to 1 g every 8-12 hours 1
- Moderately severe systemic infections: 1-2 g every 8-12 hours 1
- Severe systemic or life-threatening infections: 2 g every 6-8 hours 1
Route of Administration
The intravenous route is recommended for patients requiring single doses greater than 1 gram or those with bacterial septicemia, localized parenchymal abscess, peritonitis, or other severe systemic infections. 1 Intramuscular administration is acceptable for lower doses in less severe infections 1, 2.
Special Considerations for Pseudomonas aeruginosa
For systemic infections caused by Pseudomonas aeruginosa, 2 grams every 6-8 hours is recommended at least upon initiation of therapy due to the serious nature of these infections. 1 This higher dosing achieves MIC90 values that exceed therapeutic levels for approximately 6 hours after a 2-gram intravenous dose 3.
Pharmacokinetic Properties
Aztreonam has favorable pharmacokinetic characteristics that support the dosing intervals 2, 3:
- Serum half-life: 1.5-2.1 hours in patients with normal renal function 2, 3
- Peak levels: Achieved within 5 minutes after IV administration and approximately 1 hour after IM administration 3
- Urinary excretion: 60-70% excreted unchanged in urine, resulting in concentrations of approximately 3,000 mcg/mL two hours after a 1-gram IV dose 3
- Volume of distribution: Approximately 0.18 L/kg at steady state 3
Duration of Therapy
Aztreonam should be continued for at least 48 hours after the patient becomes asymptomatic or evidence of bacterial eradication has been obtained. 4, 1 Persistent infections may require several weeks of treatment 4, 1.
Combination Therapy Considerations
When treating metallo-β-lactamase-producing carbapenem-resistant Enterobacterales (CRE), combine aztreonam 1-2 grams IV every 6-8 hours with ceftazidime-avibactam, as this combination showed significantly lower 30-day mortality (19.2% vs 44%, P=0.007) compared to other agents 5.
For mixed infections involving gram-positive or anaerobic organisms, aztreonam must be combined with appropriate agents since it has no activity against these pathogens 2, 6.
Critical Caveats
- Do not use doses smaller than indicated, as this may compromise efficacy 1
- Aztreonam is not nephrotoxic, making it an excellent alternative to aminoglycosides in patients at risk for renal toxicity 2, 6, 7
- The drug has a strictly gram-negative aerobic spectrum, limiting its use as a single empiric agent 2, 6