What is the recommended dosage of ertapenem (a carbapenem antibiotic) for a patient with a positive urinary tract infection (UTI) and potential impaired renal function?

Ertapenem Dosage for Urinary Tract Infection

For adults with a positive UTI, administer ertapenem 1 gram intravenously once daily, infused over 30 minutes, for 10-14 days. 1

Standard Dosing by Age Group

Adults and Adolescents (≥13 years)

• 1 gram IV once daily for complicated UTI including pyelonephritis 1
• Infuse over 30 minutes 1
• Treatment duration: 10-14 days 1
• After minimum 3 days of IV therapy, may switch to appropriate oral therapy once clinical improvement demonstrated 1, 2

Pediatric Patients (3 months to 12 years)

• 15 mg/kg IV twice daily (maximum 1 gram per day) 1
• Treatment duration: 10-14 days 1

Dosing Adjustments for Renal Impairment

This is critical and commonly overlooked—ertapenem requires dose reduction in renal dysfunction:

Creatinine Clearance >30 mL/min/1.73 m²

• No adjustment needed: 1 gram daily 1

Creatinine Clearance ≤30 mL/min/1.73 m²

• Reduce to 500 mg once daily 1
• This includes patients with end-stage renal disease (CrCl ≤10 mL/min/1.73 m²) 1

Patients on Hemodialysis

• Give 500 mg daily 1
• If ertapenem administered within 6 hours before hemodialysis: give supplementary 150 mg dose after dialysis session 1
• If administered ≥6 hours before hemodialysis: no supplementary dose needed 1

Clinical Efficacy Evidence

The evidence strongly supports ertapenem for complicated UTI:

• Microbiological cure rates of 87.9-93.0% in randomized controlled trials comparing ertapenem to ceftriaxone 2, 3, 4
• Most common pathogens treated: Escherichia coli (64.7%) and Klebsiella pneumoniae (9.8%) 2
• Equivalent efficacy to ceftriaxone for acute pyelonephritis and complicated UTI 3, 4

Important Clinical Considerations

Urinary Concentrations

• Ertapenem achieves very high urinary concentrations (>128 mg/L) maintained for 40% of the dosing interval 5
• Sufficient to overcome low-to-intermediate resistance patterns 5

Factors Affecting Therapeutic Response

Renal insufficiency and urinary pH significantly impact efficacy:

• Acid urine pH + normal renal function: bacteriuria eliminated in <3 days 6
• Alkaline urine pH + renal insufficiency: time to negative cultures prolonged to >3 days 6
• Consider urinary acidification strategies in patients with alkaline urine and slow response 6

Common Pitfalls to Avoid

Do NOT:

• Mix or co-infuse ertapenem with other medications 1
• Use diluents containing dextrose (α-D-glucose) 1
• Forget dose adjustment in renal impairment—this is the most common error 1
• Use ertapenem for uncomplicated cystitis when oral options are appropriate 2

Hepatic Impairment

• No specific dose adjustment recommendations available for hepatic impairment 1
• Use with caution and monitor closely 1

Alternative Context: Fournier's Gangrene

While not standard UTI treatment, ertapenem appears in European Association of Urology guidelines for Fournier's gangrene at 1 gram once daily as part of polymicrobial coverage 7. This is a distinct indication from routine UTI.

Pharmacokinetic Parameters

• Volume of distribution: 4.8 L 5
• Clearance: 0.7 L/h 5
• Elimination half-life: 6.1 hours 5
• Median duration of parenteral therapy in clinical trials: 4-5.8 days before oral switch 2, 4