What is the recommended IV dosing of aztreonam (Aztreonam) for bacteremia?

IV Aztreonam Dosing for Bacteremia

For bacteremia caused by susceptible gram-negative organisms, administer aztreonam 2 g IV every 6-8 hours in patients with normal renal function. 1

Standard Dosing Regimen

The recommended IV dosing for aztreonam in serious infections including bacteremia is:

• 2 g IV every 6-8 hours for patients with normal renal and hepatic function 1
• 1-2 g IV every 6-8 hours is the acceptable range, with higher doses (2 g) preferred for severe infections like bacteremia 1

Clinical Context and Spectrum

Aztreonam is a monobactam antibiotic with exclusively gram-negative aerobic activity, making it particularly useful when:

• Gram-positive or anaerobic coverage is not needed 2, 3
• The patient has severe beta-lactam allergies (aztreonam has minimal cross-reactivity) 1
• Multidrug-resistant gram-negative organisms are involved, including Pseudomonas aeruginosa 4, 5

Critical limitation: Aztreonam has no activity against gram-positive bacteria or anaerobes 2, 3. For empiric bacteremia treatment before organism identification, aztreonam must be combined with agents covering gram-positive organisms (e.g., vancomycin) and anaerobes (e.g., metronidazole) if clinically indicated 3, 5.

Pharmacokinetic Considerations

• Peak serum levels after 2 g IV dosing exceed MIC90 values for most Enterobacteriaceae for 8 hours and for P. aeruginosa for approximately 6 hours 6
• Serum half-life is 1.5-2.1 hours in patients with normal renal function 3, 6
• 60-70% excreted unchanged in urine 6
• Dosage adjustment required for renal impairment - serum clearance is directly proportional to creatinine clearance 3, 6

Efficacy in Bacteremia

Clinical studies demonstrate:

• 91% bacteriologic eradication rate at end of treatment for gram-negative infections 4
• 10 of 11 bacteremia cases cured (91%), including 4 cases due to P. aeruginosa 5
• 86% overall clinical response rate in seriously ill patients with multiresistant gram-negative infections 5

Common Pitfalls to Avoid

1. Do not use aztreonam as monotherapy for empiric bacteremia - it lacks gram-positive and anaerobic coverage 3, 5
2. Adjust doses in renal dysfunction - failure to do so risks inadequate levels or accumulation 3, 6
3. For P. aeruginosa bacteremia, consider combination therapy with aminoglycosides for synergy, as monotherapy may not achieve bacteriologic cure despite clinical improvement 4, 5
4. Verify susceptibility testing - aztreonam is most effective when MIC values are ≤8 mcg/mL 6, 5

Duration of Therapy

For uncomplicated bacteremia with documented source control and negative follow-up cultures, at least 2 weeks of therapy is standard, though specific duration should be guided by clinical response and infection source 1.