What is the recommended dose of Augmentin (amoxicillin-clavulanate) for an Escherichia coli (E. coli) urinary tract infection (UTI)?

Augmentin Dosing for E. coli UTI

For uncomplicated E. coli UTI in adults, use amoxicillin-clavulanate 500 mg orally every 8 hours for 7 days, which is a second-line option when first-line agents (nitrofurantoin, fosfomycin, or pivmecillinam) are contraindicated or unavailable. 1

Standard Adult Dosing

• Amoxicillin-clavulanate 500 mg orally every 8 hours for 7 days is the recommended regimen for uncomplicated UTI caused by E. coli 2
• This dosing achieves high urinary concentrations sufficient to overcome moderate resistance patterns 3, 4
• The 7-day duration is preferred over shorter courses; 3-day treatment with amoxicillin-clavulanate showed only 55% success rates compared to 82% with 10-day treatment in pediatric studies 5

Pediatric Dosing (Ages 3 Months and Older)

• 20-40 mg/kg/day divided into 3 doses for 7-14 days 6
• For febrile UTIs in infants and children 2-24 months, the total course should be 7-14 days regardless of initial parenteral vs oral administration 6

When Augmentin Is Appropriate

Use amoxicillin-clavulanate as a second-line agent when:

• First-line agents (nitrofurantoin, fosfomycin, pivmecillinam) are contraindicated or unavailable 1
• Local E. coli resistance to trimethoprim-sulfamethoxazole or fluoroquinolones exceeds 20% 1
• Patient has documented susceptibility to amoxicillin-clavulanate on culture 1

Critical Limitations and Resistance Considerations

Important caveats about Augmentin for E. coli UTI:

• Augmentin is not effective against ESBL-producing E. coli in most cases; use nitrofurantoin, fosfomycin, or pivmecillinam instead for oral therapy 1
• For ESBL-E. coli requiring parenteral therapy, use piperacillin-tazobactam, carbapenems, or ceftazidime-avibactam 1
• Historical success rates for amoxicillin-resistant organisms treated with Augmentin were approximately 70%, indicating significant failure rates 3
• In spinal injury patients with complicated UTI, bacteriological success was only 69% at 8 days post-therapy 7

Alternative First-Line Agents for E. coli UTI

Preferred first-line options (use these before Augmentin):

• Nitrofurantoin 100 mg orally every 6 hours for 5-7 days 1
• Fosfomycin 3 g as a single oral dose 1
• Pivmecillinam (where available) for 5 days 1

These agents maintain better activity against resistant E. coli strains and should be prioritized over amoxicillin-clavulanate 1

When to Escalate Therapy

Consider parenteral therapy or alternative agents if:

• Patient appears toxic or cannot tolerate oral medications 6
• ESBL-producing E. coli is suspected or confirmed 1
• Carbapenem-resistant E. coli (CRE) is identified—use ceftazidime-avibactam 2.5 g IV every 8 hours, meropenem-vaborbactam 4 g IV every 8 hours, or imipenem-cilastatin-relebactam 1.25 g IV every 6 hours 6
• Patient has complicated UTI with pyelonephritis or bacteremia requiring longer duration therapy 2

Common Pitfalls to Avoid

• Do not use Augmentin empirically without knowing local resistance patterns; high rates of amoxicillin resistance in E. coli make this a poor empiric choice in many communities 1
• Do not use nitrofurantoin for febrile UTIs or pyelonephritis in children, as it does not achieve adequate tissue concentrations 6
• Do not extend treatment beyond 7 days for uncomplicated UTI without clear indication, as this increases resistance risk without proven benefit 2
• Obtain urine culture and susceptibility testing before initiating therapy when possible to guide appropriate antibiotic selection 2