What dose and duration of IV meropenem (Invanz) should be used for a urinary tract infection in a 62‑year‑old woman with impaired renal function (serum creatinine 1.27 mg/dL, eGFR ≈48 mL/min)?

Important Clarification: Invanz is NOT Meropenem

Invanz (ertapenem) is a different carbapenem antibiotic than meropenem, and the provided evidence primarily addresses meropenem dosing, not ertapenem. For a 62-year-old woman with a GFR of 48 mL/min and creatinine 1.27 mg/dL, ertapenem (Invanz) should be dosed at 500 mg IV once daily for 5-7 days for a complicated urinary tract infection.

Critical Dosing Information for Ertapenem (Invanz)

Renal Dose Adjustment

• For patients with creatinine clearance 30-50 mL/min (which includes your patient with GFR 48): Reduce the standard 1 gram daily dose to 500 mg IV once daily 1
• The once-daily dosing advantage of ertapenem is maintained even with renal impairment, unlike meropenem which requires more frequent dosing adjustments 2, 3

Treatment Duration

• For complicated urinary tract infections: 5-7 days is recommended 1
• This duration applies to older patients with comorbidities, provided there is adequate clinical response 1
• Treatment should be individualized based on source control, underlying comorbidities, and initial response to therapy 1

Clinical Considerations for This Patient Population

Age and Frailty Factors

• At 62 years old with moderate renal impairment (CKD Stage 3a), this patient requires careful monitoring for both efficacy and adverse events 1
• Older patients with UTIs may present with atypical symptoms such as confusion, functional decline, or falls rather than classic dysuria 1

Monitoring Requirements

• Renal function should be reassessed at 48-72 hours if clinical response is inadequate, as renal function may decline during treatment in elderly patients 4
• Monitor for drug-related adverse events, particularly in the context of polypharmacy common in this age group 1

Important Pitfalls to Avoid

Drug Confusion

• Do not confuse Invanz (ertapenem) with meropenem or imipenem - they are different carbapenems with distinct dosing schedules and renal adjustment requirements 5, 2, 6
• Ertapenem has the advantage of once-daily dosing, making it more convenient for outpatient parenteral therapy

Underdosing Risk

• Failure to adjust the dose from 1 gram to 500 mg daily in moderate renal impairment risks drug accumulation and toxicity 1
• Conversely, using too conservative a dose may lead to treatment failure, particularly with resistant organisms 2, 6

Alternative Considerations

• If the patient has severe renal impairment (GFR <30 mL/min) or is on hemodialysis, ertapenem dosing becomes more complex and alternative agents may be preferred 1
• For carbapenem-resistant organisms, alternative regimens such as ceftazidime/avibactam would be needed 1