What antibiotics are used to treat Pseudomonas aeruginosa infections?

Antibiotics for Pseudomonas aeruginosa Infections

For Pseudomonas aeruginosa infections, combination therapy with an antipseudomonal β-lactam (such as piperacillin-tazobactam, cefepime, or meropenem) plus either a fluoroquinolone (preferably ciprofloxacin) or an aminoglycoside (such as amikacin or tobramycin) is recommended as first-line treatment. 1

First-Line Intravenous Options

Antipseudomonal β-lactams:

• Piperacillin-tazobactam: 4.5g IV every 6 hours 1, 2
• Ceftazidime: 2g IV every 8 hours or 150-250 mg/kg/day divided in 3-4 doses 3
• Meropenem: 1g IV every 8 hours or 60-120 mg/kg/day divided in 3 doses 3, 1
• Imipenem-cilastatin: 1g IV every 8 hours or 50-100 mg/kg/day divided in 3-4 doses 3, 1
• Aztreonam: 2g IV every 6-8 hours or 150 mg/kg/day divided in 4 doses 3

Plus one of the following:

Fluoroquinolones:

• Ciprofloxacin: 400mg IV every 8 hours 1, 4

Aminoglycosides:

• Tobramycin: 5-10 mg/kg/day divided in 1-3 doses (monitor serum levels) 3
• Amikacin: 15-20 mg/kg IV once daily (monitor serum levels) 3, 1

Treatment Considerations

Nosocomial Pneumonia

For Pseudomonas pneumonia, particularly nosocomial:

• Piperacillin-tazobactam 4.5g IV every 6 hours plus an aminoglycoside 2
• Treatment duration: 7-14 days 1
• Continue aminoglycoside therapy in patients from whom P. aeruginosa is isolated 2

Oral Step-Down Therapy

When clinically improved (afebrile for ≥24 hours, functioning GI tract, decreasing WBC count):

• Ciprofloxacin: 500mg PO twice daily 1, 4
• Levofloxacin: 750mg PO daily (alternative) 1

Special Considerations

Difficult-to-treat strains:

• Ceftolozane-tazobactam: 1.5-3g IV every 8 hours 1
• Alternative options: ceftazidime-avibactam, cefiderocol, or imipenem-relebactam 1

For cystic fibrosis patients:

• Higher doses are often required due to altered pharmacokinetics 3
• Consider continuous infusion for beta-lactams 3, 5
• Inhaled antibiotics (colistin, tobramycin) may be used for maintenance therapy 3, 6

Dosing in Renal Impairment

For patients with creatinine clearance ≤40 mL/min, dose adjustment is necessary:

• For creatinine clearance 20-40 mL/min: Piperacillin-tazobactam 2.25g IV every 6 hours 2
• For creatinine clearance <20 mL/min: Piperacillin-tazobactam 2.25g IV every 8 hours 2
• For hemodialysis patients: Additional dose after dialysis 2

Monitoring and Assessment

• Regular sputum cultures during and after therapy to monitor bacterial response 1
• Monitor renal function and drug levels when using aminoglycosides 1
• Assess for clinical improvement: decreased sputum production, improved respiratory symptoms, and improved lung function 1

Important Considerations

• Extended infusion of piperacillin-tazobactam (over 3-4 hours) may improve outcomes in critically ill patients with P. aeruginosa infections 5
• Recent studies suggest that ceftazidime or piperacillin-tazobactam may be preferred over carbapenems for susceptible P. aeruginosa infections to reduce the development of resistance 7
• Combination therapy is particularly important for severe infections, immunocompromised patients, or when antibiotic resistance is suspected 1, 8
• De-escalate to monotherapy based on susceptibility results when the patient is clinically improving 1

Pitfalls to Avoid

• Inadequate dosing in cystic fibrosis patients (higher doses needed) 3
• Failure to monitor aminoglycoside levels, which can lead to nephrotoxicity and ototoxicity 1
• Delayed initiation of appropriate therapy, which is associated with increased mortality 9
• Failure to consider local resistance patterns when selecting empiric therapy 1
• Unnecessary prolonged antibiotic exposure, which may select for resistant organisms 1