Aztreonam Dosing for Adults
For adults with normal renal function, administer aztreonam 1-2 g IV every 6-8 hours for most serious infections, with 2 g every 6-8 hours recommended for severe systemic infections or Pseudomonas aeruginosa. 1
Standard Dosing in Normal Renal Function
The FDA-approved dosing varies by infection 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
- Pseudomonas aeruginosa infections: 2 g every 6-8 hours is specifically recommended at least upon initiation of therapy 1
For hospital-acquired pneumonia requiring antipseudomonal coverage, the IDSA/ATS guidelines recommend 2 g IV every 8 hours 2. For complicated intra-abdominal infections, the IDSA/SIS guidelines recommend 1-2 g every 6-8 hours 2. The maximum recommended daily dose is 8 g 1.
The intravenous route is mandatory for patients requiring single doses greater than 1 g or those with bacterial septicemia, localized parenchymal abscess, peritonitis, or other severe systemic or life-threatening infections 1.
Dosing Adjustments in Renal Impairment
Aztreonam clearance correlates directly with creatinine clearance (r² = 0.90), necessitating dose adjustments in renal dysfunction 3, 4. The FDA label provides specific guidance 1:
Moderate renal impairment (CrCl 10-30 mL/min/1.73 m²):
- Give usual loading dose (1-2 g) initially 1
- Reduce maintenance dose to one-half the usual dose at the usual interval (every 6,8, or 12 hours) 1
Severe renal impairment (CrCl <10 mL/min/1.73 m²), including hemodialysis patients:
- Give usual loading dose (500 mg, 1 g, or 2 g) initially 1
- Reduce maintenance dose to one-fourth the usual initial dose at the usual interval 1
- For serious/life-threatening infections, give an additional one-eighth of the initial dose after each hemodialysis session 1
Population pharmacokinetic modeling confirms these adjustments achieve adequate probability of target attainment (>90% PTA) for organisms with MIC ≤4-8 mg/L 4.
Creatinine Clearance Estimation
When only serum creatinine is available, use the Cockcroft-Gault equation 1:
- Males: CrCl = [weight (kg) × (140 - age)] / [72 × serum creatinine (mg/dL)] 1
- Females: 0.85 × male calculation 1
The serum creatinine must represent steady-state renal function 1.
Special Populations
Elderly patients: Renal status is the major determinant of dosage 1. Serum creatinine may not accurately reflect renal function in elderly patients, so creatinine clearance estimates should be obtained and dosage modifications made accordingly 1.
Pediatric patients (age 1 month to 12 years) with normal renal function 1:
- Mild to moderate infections: 30 mg/kg every 8 hours 1, 5
- Moderate to severe infections: 30 mg/kg every 6-8 hours 1, 5
- Maximum: 120 mg/kg/day 1, 5
- Insufficient data exist for dosing in pediatric patients with renal impairment 5
Treatment Duration
Continue aztreonam for at least 48 hours after the patient becomes asymptomatic or evidence of bacterial eradication is obtained 1, 6. Persistent infections may require several weeks of treatment 1, 6. For Pseudomonas aeruginosa pneumonia, 14 days is the typical duration 2.
Pharmacokinetic Considerations
Aztreonam has a half-life of 1.5-2.1 hours in normal renal function, increasing to 1.6-8.9 hours with renal impairment 7, 3. The volume of distribution approximates extracellular fluid volume (0.16-0.18 L/kg) 8, 3. Extended infusions may optimize pharmacokinetic/pharmacodynamic properties, particularly for organisms with higher MICs 2.