What is the recommended dosage of meropenem (Merrem) for a patient with a urinary tract infection (UTI) and potential impaired renal function?

Meropenem Dosage for UTI

For complicated urinary tract infections, administer meropenem 1 gram intravenously every 8 hours over 15-30 minutes for 5-7 days, with dose adjustments required for renal impairment. 1

Standard Dosing for UTI

• The FDA-approved dose for complicated UTIs is 1 gram IV every 8 hours, administered as an infusion over 15-30 minutes 1
• This dosing regimen has demonstrated 98.4% overall success rates (clinical cure plus microbial eradication) in complicated UTI including acute pyelonephritis 2
• Treatment duration should be 5-7 days for complicated UTIs caused by carbapenem-resistant Enterobacterales (CRE) 3

Dosing Adjustments for Renal Impairment

Dose reduction is mandatory in patients with decreased kidney function to prevent drug accumulation and toxicity 1, 4:

• Creatinine clearance >50 mL/min: 1 gram every 8 hours (standard dose) 1
• Creatinine clearance 26-50 mL/min: 1 gram every 12 hours 1
• Creatinine clearance 10-25 mL/min: 500 mg every 12 hours 1
• Creatinine clearance <10 mL/min: 500 mg every 24 hours 1

The half-life of meropenem extends from approximately 1 hour in healthy individuals to up to 13.7 hours in anuric patients with end-stage renal disease, making dose adjustment critical 4, 5

Special Considerations for Dialysis Patients

• Hemodialysis removes approximately 50% of meropenem, requiring supplemental dosing after dialysis sessions 4
• For patients on continuous venovenous hemofiltration (CVVHF), 25-50% of the drug is eliminated 4
• For continuous venovenous hemodiafiltration (CVVHDF), 13-53% is removed 4

Context for Multidrug-Resistant Organisms

When treating complicated UTIs caused by carbapenem-resistant Enterobacterales, alternative carbapenem combinations are preferred over standard meropenem 3:

• Meropenem-vaborbactam 4 grams (2g meropenem + 2g vaborbactam) IV every 8 hours is specifically recommended for CRE-associated UTIs 3
• This combination demonstrated superior outcomes in the TANGO-II trial for CRE infections including UTI 3
• Standard meropenem 1 gram every 8 hours by extended infusion (over 3 hours) may be used in combination with colistin for CRE when newer agents are unavailable 3

Common Pitfalls to Avoid

• Failing to adjust doses for renal function leads to drug accumulation and increased seizure risk, particularly since meropenem's half-life increases 13-fold in anuric patients 4, 5
• Underdosing in dialysis patients is common due to variable drug removal rates depending on the specific renal replacement modality used 4
• Using standard meropenem monotherapy for suspected or confirmed CRE infections without susceptibility testing, as resistance rates are high and newer carbapenem combinations (meropenem-vaborbactam) show superior efficacy 3
• Administering meropenem as a rapid bolus instead of the recommended 15-30 minute infusion, which can increase infusion-related adverse effects 1, 6

Pharmacokinetic Considerations

• Peak plasma concentrations reach approximately 53-62 mg/L after 1 gram IV in patients with normal renal function 4, 5
• The volume of distribution is 21L, indicating predominantly extracellular distribution 5
• Up to 70% is recovered unchanged in urine, making renal function the primary determinant of dosing 5
• Meropenem has excellent tolerability with lower nephrotoxicity and neurotoxicity compared to imipenem, and does not require coadministration with cilastatin 6, 5