What is the appropriate dosing of Meropenem for a patient with a sputum infection and pseudomonas, considering factors such as age, weight, and renal function?

Meropenem Dosing for Pseudomonas Sputum Infection

For a patient with Pseudomonas aeruginosa respiratory tract infection, administer meropenem 1 gram IV every 8 hours as a 30-minute infusion, with mandatory dose adjustment if creatinine clearance is ≤50 mL/min. 1

Standard Dosing for Pseudomonas Respiratory Infections

• The FDA-approved dose for Pseudomonas infections is specifically 1 gram every 8 hours, not the lower 500 mg dose used for non-Pseudomonas infections. 1
• Administer as a 30-minute intravenous infusion over 15-30 minutes, or alternatively as a bolus injection over 3-5 minutes for the 1 gram dose. 1
• The IDSA guidelines for vertebral osteomyelitis (which provides dosing references for Pseudomonas across infection types) confirm meropenem 1 gram IV every 8 hours as appropriate for Pseudomonas aeruginosa. 2

Critical Renal Function Adjustments

You must reduce the dose if creatinine clearance is ≤50 mL/min, as standard dosing only applies to CrCl >50 mL/min. 1

• CrCl 26-50 mL/min: Give 1 gram every 12 hours (not every 8 hours). 1
• CrCl 10-25 mL/min: Give 500 mg every 12 hours. 1
• CrCl <10 mL/min: Give 500 mg every 24 hours. 1
• Calculate creatinine clearance using the Cockcroft-Gault equation when only serum creatinine is available. 1

Augmented Renal Clearance Considerations

In critically ill patients with preserved or augmented renal function (CrCl >100 mL/min), standard dosing may be insufficient for Pseudomonas. 3

• Recent pharmacokinetic data from septic shock patients demonstrates that 2 grams every 8 hours may be required for empirical Pseudomonas coverage in patients with augmented renal clearance. 3
• However, the FDA label does not support doses exceeding 1 gram every 8 hours for standard infections, so this represents off-label dosing that should be reserved for severe infections with documented or high suspicion of resistant organisms. 1
• Consider prolonged infusion (3 hours) or continuous infusion strategies if treating pathogens with elevated MICs or in patients with augmented renal clearance. 3

Common Pitfalls to Avoid

• Do not use 500 mg every 8 hours for Pseudomonas infections—this dose is only for non-Pseudomonas skin/soft tissue infections. 1
• Do not continue standard every-8-hour dosing in patients with even mild renal impairment (CrCl 26-50 mL/min)—you must extend the interval to every 12 hours. 1
• Meropenem exhibits time-dependent killing, so maintaining free drug concentrations above the MIC for 40-100% of the dosing interval is critical for efficacy. 4, 5
• Large inter-patient variability exists in critically ill patients, with standard dosing achieving adequate targets in only 48.4% of patients for MIC 2 mg/L and 20.6% for MIC 8 mg/L. 4

Combination Therapy Considerations

• The IDSA guidelines note that double coverage (β-lactam plus ciprofloxacin or β-lactam plus aminoglycoside) may be considered for Pseudomonas vertebral osteomyelitis, though this is optional rather than mandatory. 2
• For respiratory Pseudomonas infections in critically ill patients, combination therapy should be considered for septic shock, ARDS, or prior MDRO colonization. 6

Treatment Duration

• The typical duration for Pseudomonas aeruginosa lung infections is 14 days, though this should be adjusted based on clinical response and source control. 7
• The IDSA recommends 6 weeks of therapy for Pseudomonas vertebral osteomyelitis. 2