What is the recommended dose of aztreonam (Aztreonam) for lung infection?

Aztreonam Dosing for Lung Infections

For systemic lung infections caused by gram-negative bacteria, administer aztreonam 2 grams IV every 6-8 hours, with the 2 gram every 6 hour regimen preferred for Pseudomonas aeruginosa infections. 1

Standard Intravenous Dosing

Hospital-Acquired and Ventilator-Associated Pneumonia

• Administer 2 grams IV every 8 hours for antipseudomonal coverage in nosocomial pneumonia 1
• This dosing achieves adequate serum concentrations exceeding MIC90 values for most Enterobacteriaceae for 8 hours and for P. aeruginosa for approximately 6 hours 2

Pseudomonas aeruginosa Lung Infections

• Use 2 grams IV every 6 hours for confirmed or suspected Pseudomonas pneumonia 3
• Consider combination therapy with an aminoglycoside (gentamicin or tobramycin) or colistin, as aztreonam demonstrates synergistic activity against P. aeruginosa when combined with these agents 3, 2
• Patients can demonstrate clinical response despite in vitro resistance patterns 3

Moderate Severity Infections

• For less severe gram-negative lung infections, 1-2 grams every 6-8 hours is appropriate 1, 4
• Doses of 1 gram every 8-12 hours are adequate for most Enterobacteriaceae infections 5

Inhaled Aztreonam for Cystic Fibrosis

Dosing Regimen

• Administer 75 mg inhaled three times daily for chronic P. aeruginosa suppression in CF patients with moderate to severe lung disease (FEV1 25-75% predicted) 3
• Alternative dosing studied includes 75-225 mg administered two to three times daily 3
• Twice-daily dosing (rather than three times daily) demonstrated superior time to exacerbation (92 vs 71 days, P=0.002) 3

Treatment Duration and Cycling

• Initial treatment courses are typically 28 days 3
• Long-term use follows an every-other-month cycling pattern (28 days on, 28 days off) for chronic suppression 3
• This regimen improves FEV1 by 6.3-10.3% absolute improvement, reduces hospitalizations (0.5 vs 1.5 days, P=0.049), and improves quality of life 3

Extended Infusion Strategy

Consider administering each 2 gram dose as a prolonged infusion over 3-4 hours rather than standard 30-minute infusions to maximize time above MIC 1, 6

• This approach is particularly valuable for pathogens with higher MICs or critically ill patients 1, 6
• A case report demonstrated that 2 grams infused over 4 hours every 6 hours achieved plateau concentrations of 71 mg/L, successfully maintaining concentrations above MIC for >40% of the dosing interval 6
• Extended infusions optimize the time-dependent killing characteristics of beta-lactam antibiotics 1

Renal Dose Adjustment

Aztreonam clearance is directly proportional to creatinine clearance, requiring dose reduction in renal impairment 2, 7

• Between 60-70% of aztreonam is excreted unchanged in urine 2
• The serum half-life in normal renal function is 1.5-2.1 hours 7
• Specific dose adjustments must be made based on creatinine clearance, though the provided guidelines do not specify exact reductions 2, 7

Combination Therapy Considerations

Carbapenem-Resistant Organisms

• For metallo-beta-lactamase producing organisms (NDM-producing CRE), combine aztreonam with ceftazidime-avibactam 3
• This combination demonstrates excellent in vitro synergy, as aztreonam is not hydrolyzed by metallo-beta-lactamases 3
• This regimen reduced 30-day mortality from 44% to 19.2% (P=0.007) in bloodstream infections 3

Coverage Gaps

• Aztreonam has NO activity against gram-positive bacteria or anaerobes 4, 2, 7, 5
• Always combine with agents covering gram-positive organisms (e.g., vancomycin for MRSA, flucloxacillin for MSSA) and anaerobes (e.g., metronidazole) in polymicrobial lung infections 7, 5
• This is critical in aspiration pneumonia, lung abscesses, or empiric therapy before culture results 7, 5

Treatment Duration

Administer aztreonam for 14 days for confirmed Pseudomonas aeruginosa lung infections 3

• Shorter courses may suffice in mild bronchiectasis without P. aeruginosa 3
• Standard duration for other gram-negative pneumonias is typically 7-14 days depending on severity 3

Common Pitfalls

• Do not use aztreonam as monotherapy for empiric pneumonia - its strictly gram-negative aerobic spectrum leaves dangerous coverage gaps for gram-positive and anaerobic pathogens 7, 5
• Aztreonam is significantly less nephrotoxic than aminoglycosides, making it an excellent alternative in patients with renal insufficiency or those at high risk for aminoglycoside toxicity 4, 7
• Unlike imipenem, aztreonam is not associated with seizures and has minimal immunogenicity 4, 7