Meropenem Dosing for ESBL UTI in an 87-Year-Old Patient
For an 87-year-old patient with ESBL UTI, meropenem should be dosed at 500 mg every 12 hours if creatinine clearance is 26-50 mL/min, or 500 mg every 24 hours if creatinine clearance is less than 10 mL/min. 1
Dosing Based on Renal Function
Meropenem dosing must be adjusted according to renal function in elderly patients. The FDA-approved dosing recommendations for adults with renal impairment are as follows 1:
- CrCl >50 mL/min: 500 mg every 8 hours
- CrCl 26-50 mL/min: 500 mg every 12 hours
- CrCl 10-25 mL/min: 250 mg (half dose) every 12 hours
- CrCl <10 mL/min: 250 mg (half dose) every 24 hours
Assessment of Renal Function in Elderly Patients
In an 87-year-old patient, renal function assessment is critical before initiating meropenem therapy:
- Calculate creatinine clearance using the Cockcroft-Gault equation
- Consider that elderly patients (>65 years) typically have reduced renal function even with normal serum creatinine levels 2
- Monitor renal function throughout treatment as acute kidney injury can occur during severe infections 3
Administration Considerations
- Administer meropenem as an intravenous infusion over 15-30 minutes 1
- Extended infusions (over 3 hours) may improve target attainment in patients with higher creatinine clearance 4
- For critically ill elderly patients with ESBL UTI, consider therapeutic drug monitoring if available 5
Clinical Considerations for ESBL UTI
- Obtain urine culture before initiating antibiotics to confirm the causative pathogen 3
- Expect clinical improvement within 48-72 hours of starting adequate treatment 3
- Consider repeat urine culture if symptoms persist beyond this timeframe 3
Monitoring During Treatment
- Monitor renal function regularly during treatment
- Watch for adverse events, although meropenem has an excellent safety profile in elderly and renally impaired patients 2
- Seizures are rare (0.1%) even in patients with renal impairment 2
Duration of Therapy
For complicated UTIs in elderly patients with ESBL-producing organisms, a 7-14 day course is typically recommended, similar to the duration for other complicated UTIs 3.
Important Caveats
- Elderly patients have significantly lower meropenem clearance compared to younger patients due to reduced renal function 4
- Large inter-patient variability in meropenem concentrations exists in critically ill patients 5
- Underdosing should be avoided despite renal adjustment due to the severity of ESBL infections 6
- For patients with augmented renal function (rare in elderly), standard dosing may be insufficient 5
Remember that proper dosing of meropenem in elderly patients with ESBL UTI requires balancing adequate antimicrobial coverage against the risk of toxicity from impaired drug clearance.