Aztreonam Dosing Per Kilogram
For adults, aztreonam is dosed at 1-2 grams every 6-8 hours (not weight-based), while for pediatric patients the recommended dose is 30 mg/kg every 6-8 hours, with a maximum of 120 mg/kg/day for severe infections. 1
Adult Dosing
Adult dosing is not weight-based but rather fixed-dose regimens 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 or life-threatening infections: 2 g every 6-8 hours 1
- Pseudomonas aeruginosa infections: 2 g every 6-8 hours is recommended at least initially due to the serious nature of these infections 1
The 2016 IDSA/ATS guidelines for hospital-acquired pneumonia recommend 2 g IV every 8 hours for antipseudomonal coverage 2. For complicated intra-abdominal infections, the 2010 IDSA/SIS guidelines recommend 1-2 g every 6-8 hours 2.
Pediatric Dosing
Pediatric dosing is weight-based 1:
- Mild to moderate infections: 30 mg/kg every 8 hours 1
- Moderate to severe infections: 30 mg/kg every 6-8 hours 1
- Maximum daily dose: 120 mg/kg/day 1
The American Academy of Pediatrics recommends 30 mg/kg every 8 hours for mild to moderate infections, with the maximum of 120 mg/kg/day reserved for moderate to severe infections 3. Aztreonam should be administered intravenously to pediatric patients with normal renal function 1.
Renal Impairment Adjustments
Dosing must be adjusted in renal dysfunction because 60-70% of aztreonam is excreted unchanged in urine 4:
- Creatinine clearance 10-30 mL/min/1.73m²: Halve the usual dose after an initial loading dose of 1-2 g 1
- Creatinine clearance <10 mL/min/1.73m²: Give usual initial dose (500 mg, 1 g, or 2 g), then maintenance dose of one-fourth the usual dose at standard intervals 1
- Hemodialysis patients: Add one-eighth of the initial dose after each dialysis session 1
Serum clearance of aztreonam correlates directly with creatinine clearance (r² = 0.90), with a mean CL/CLCR ratio of 1.11 5. The elimination half-life ranges from 1.6 hours in normal renal function to 8.9 hours in renal impairment 5.
Pharmacokinetic Considerations
Extended infusions may be appropriate for pharmacokinetic/pharmacodynamic optimization 2. The drug has an average elimination half-life of 1.7 hours in patients with normal renal function 4. After a 2 g IV dose, MIC90 values for most Enterobacteriaceae are exceeded for 8 hours, and for Pseudomonas aeruginosa for almost 6 hours 4.
The steady-state volume of distribution is approximately 0.16-0.18 L/kg, approximating extracellular fluid volume 4, 5. Peak serum levels occur within 5 minutes after IV dosing and approximately 1 hour after IM dosing 4.
Important Caveats
Elderly patients require special attention to renal function, as serum creatinine may not accurately reflect renal status 1. Creatinine clearance estimates should be obtained and dosing adjusted accordingly 1. Studies in elderly patients with renal insufficiency have demonstrated safety even with diminished renal function, with no significant accumulation when appropriately dosed 6, 7.
There are insufficient data regarding intramuscular administration to pediatric patients or dosing in pediatric patients with renal impairment 1.