Is Invanz (ertapenem) effective for treating Pseudomonas urinary tract infections (UTIs)?

Ertapenem (Invanz) Is Not Effective for Pseudomonas UTIs

Ertapenem is ineffective against Pseudomonas aeruginosa UTIs and should not be used for this purpose. 1, 2, 3

Why Ertapenem Fails Against Pseudomonas

Ertapenem belongs to Group 1 carbapenems, which have several key limitations:

• Group 1 carbapenems (including ertapenem) have activity against extended-spectrum beta-lactamase (ESBL)-producing pathogens but do not have activity against Pseudomonas aeruginosa 1
• Ertapenem has "restricted activity against nosocomial pathogens such as Pseudomonas aeruginosa" as explicitly stated in multiple studies 2, 3
• The structural characteristics of ertapenem (1β-methyl carbapenem) contribute to its lack of activity against Pseudomonas species

Appropriate Antibiotic Options for Pseudomonas UTIs

For Pseudomonas UTIs, the following options are recommended instead:

For Pseudomonas aeruginosa susceptible to other antimicrobials:

• Piperacillin 3-4g IV q6h
• Piperacillin/tazobactam 3.375-4.5g IV q6h
• Ceftazidime 2g IV q8h
• Cefepime 2g IV q8-12h
• Ciprofloxacin 400mg IV q8h
• Levofloxacin 750mg IV daily
• Amikacin 15mg/kg IV daily (for urinary tract infections only) 1

For difficult-to-treat Pseudomonas aeruginosa (DTR-PA):

• Colistin monotherapy or combination therapy
• Ceftolozane/tazobactam 1.5-3g IV q8h
• Ceftazidime/avibactam 2.5g IV q8h
• Imipenem/cilastatin/relebactam 1.25g IV q6h 1

Group 2 Carbapenems for Pseudomonas

If a carbapenem is required for Pseudomonas UTI, only Group 2 carbapenems should be used:

• Group 2 carbapenems (imipenem/cilastatin, meropenem, doripenem) have activity against non-fermentative gram-negative bacilli including Pseudomonas 1
• These should be reserved for severe infections or when other options aren't available due to antimicrobial stewardship concerns

Clinical Implications and Pitfalls

Common Pitfalls

1. Misunderstanding carbapenem spectrum: Not all carbapenems have the same spectrum of activity. Ertapenem specifically lacks activity against Pseudomonas.

2. Inappropriate empiric therapy: Starting ertapenem empirically when Pseudomonas is suspected could lead to treatment failure and worsening infection.

3. Failure to obtain cultures: Always obtain urine cultures before starting antibiotics to guide appropriate therapy.

Treatment Duration

For Pseudomonas UTIs, treatment duration should typically be:

• 5-10 days for complicated UTI
• 10-14 days for hospital-acquired infections or bloodstream infections 1

Special Considerations

• Aminoglycosides (like amikacin) should be used with caution in elderly patients or those with renal impairment 4
• For patients with recurrent or persistent UTIs, evaluation for underlying urological abnormalities is essential
• Adequate hydration should be encouraged during treatment 4

In conclusion, when treating suspected or confirmed Pseudomonas UTIs, ertapenem is not an appropriate choice due to its inherent lack of activity against this organism. Alternative antibiotics with anti-pseudomonal activity should be selected based on susceptibility testing.