What is the recommended dosage of meropenem (Merrem) for a patient with hospital-acquired pneumonia, considering factors such as renal function and weight?

Meropenem Dosage for Hospital-Acquired Pneumonia

For hospital-acquired pneumonia, administer meropenem 1 gram IV every 8 hours, which is the standard dose recommended by the IDSA/ATS guidelines for empiric coverage of gram-negative pathogens including Pseudomonas aeruginosa. 1

Standard Dosing Regimen

• Meropenem 1 gram IV every 8 hours is the guideline-recommended dose for hospital-acquired pneumonia in patients without high mortality risk or recent antibiotic exposure 1
• For patients at high risk of mortality (requiring ventilatory support or septic shock) or with recent IV antibiotic use within 90 days, meropenem 1 gram IV every 8 hours should be combined with a second antipseudomonal agent from a different class (fluoroquinolone or aminoglycoside) 1
• The alternative carbapenem dosing is imipenem 500 mg IV every 6 hours, though meropenem is preferred due to its longer half-life and more convenient dosing schedule 1

Renal Dose Adjustments

• Dosage adjustments are mandatory for creatinine clearance ≤50 mL/min, as meropenem clearance directly correlates with renal function 2
• Meropenem is hemodialyzable, and approximately 70% of the dose is excreted unchanged in urine within 12 hours 2
• For patients on hemodialysis, meropenem and its metabolite are readily removed by dialysis, requiring post-dialysis dosing 2

MRSA Coverage Considerations

• Add vancomycin 15 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) OR linezolid 600 mg IV every 12 hours if any of the following MRSA risk factors are present: 1
  • IV antibiotic use within prior 90 days 1
  • Treatment in a unit where MRSA prevalence among S. aureus isolates is >20% or unknown 1
  • High risk of mortality (ventilatory support due to pneumonia or septic shock) 1

Optimizing Pharmacodynamics

• Extended infusion (3 hours) of meropenem 2 grams every 8 hours achieves superior pharmacodynamic targets in both plasma and epithelial lining fluid compared to standard intermittent infusion, particularly for organisms with MICs approaching the susceptibility breakpoint 3
• The percentage of time that unbound plasma concentration exceeds the MIC (T>MIC) is the pharmacodynamic parameter that best correlates with efficacy 2
• For critically ill patients or those with severe pneumonia, consider meropenem 2 grams IV every 8 hours infused over 3 hours to maximize bacterial kill and suppress emergence of resistance 4, 3

Duration of Therapy

• Treatment duration should be 7-8 days for patients responding adequately to therapy 1
• Clinical stability criteria for potential treatment discontinuation include temperature ≤37.8°C, heart rate ≤100 bpm, respiratory rate ≤24 breaths/min, and systolic BP ≥90 mmHg 5

Common Pitfalls to Avoid

• Do not use meropenem monotherapy in high-risk patients (septic shock, mechanical ventilation, or recent antibiotic exposure within 90 days) without adding a second antipseudomonal agent, as this increases risk of treatment failure and emergence of resistance 1, 4
• Avoid underdosing in critically ill patients, as suboptimal concentrations in epithelial lining fluid contribute to treatment failure and resistance emergence through mechanisms including porin loss, efflux upregulation, and increased AmpC expression 4
• Do not assume MRSA coverage is needed in all cases—only add vancomycin or linezolid when specific risk factors are present, as unnecessary broad-spectrum coverage contributes to antimicrobial resistance 1
• Meropenem plasma protein binding is only 2%, meaning renal dysfunction significantly impacts drug clearance and requires dose adjustment 2