Aztreonam Dosing for a 60 kg Patient with Normal Renal and Hepatic Function
For a 60 kg adult patient with normal renal and hepatic function, administer aztreonam 1-2 grams intravenously every 6-8 hours, with the specific dose and interval determined by infection severity. 1
Standard Dosing Regimens by Infection Severity
The dosing of aztreonam follows a tiered approach based on infection type and severity 1:
- Urinary tract infections: 500 mg or 1 g every 8-12 hours 1
- Moderately severe systemic infections: 1 g or 2 g every 8-12 hours 1
- Severe systemic or life-threatening infections: 2 g every 6-8 hours 1
For Pseudomonas aeruginosa infections specifically, 2 g every 6-8 hours is recommended at least initially, regardless of other severity considerations. 1 This higher dosing reflects the organism's relative resistance compared to other Enterobacteriaceae 2, 3.
Route of Administration Considerations
The intravenous route is strongly preferred for 1:
- Single doses greater than 1 g
- Bacterial septicemia
- Localized parenchymal abscesses (e.g., intra-abdominal abscess)
- Peritonitis
- Other severe systemic or life-threatening infections
Intramuscular administration may be acceptable for lower-severity infections requiring ≤1 g doses 1.
Pharmacokinetic Rationale
After a 2 g intravenous dose, aztreonam maintains concentrations above the MIC90 for most Enterobacteriaceae for 8 hours and for P. aeruginosa for almost 6 hours 2. The elimination half-life is approximately 1.7 hours in patients with normal renal function 2, 3. Peak serum levels occur within 5 minutes after intravenous administration 2.
Between 60-70% of aztreonam is excreted unchanged in the urine, resulting in urinary concentrations approximating 3,000 mcg/mL two hours after a 1 g intravenous dose 2.
Maximum Daily Dose
The maximum recommended dose is 8 grams per day. 1 This ceiling should not be exceeded even in severe infections.
Duration of Therapy
Continue aztreonam for at least 48 hours after the patient becomes asymptomatic or evidence of bacterial eradication has been obtained 1. Persistent infections may require treatment for several weeks 1. For complicated intra-abdominal infections specifically, antimicrobial therapy should be limited to 4-7 days unless adequate source control is difficult to achieve 1.
Important Clinical Caveats
No dose adjustment is required for this 60 kg patient with normal renal and hepatic function. 1, 4 Dosage modifications are only necessary when creatinine clearance falls below 30 mL/min/1.73 m² 1, 4.
Aztreonam has no activity against gram-positive bacteria or anaerobes 2, 3, 5. If the infection etiology is unknown or mixed bacterial infection is suspected, aztreonam must be combined with agents active against gram-positive organisms and/or anaerobes. 1, 3, 5, 6 Common combinations include aztreonam with metronidazole for intra-abdominal infections 1.
The drug is not nephrotoxic and represents a safer alternative to aminoglycosides in patients at risk for renal toxicity 2, 3, 7. Aztreonam demonstrates synergistic activity when combined with aminoglycosides against P. aeruginosa and gentamicin-resistant gram-negative rods 2.