What antibiotic with no more than twice-daily dosing is recommended for an 85-year-old woman with Chronic Kidney Disease (CKD) stage II and a Urinary Tract Infection (UTI) caused by Escherichia coli (E. coli)?

Antibiotic Recommendation for UTI in an 85-Year-Old Woman with CKD II

For an 85-year-old woman with CKD stage II and a UTI caused by E. coli, I recommend fosfomycin 3g as a single oral dose or amoxicillin-clavulanate 500mg/125mg twice daily, depending on local resistance patterns.

First-Line Options with Once or Twice Daily Dosing

Fosfomycin

• Single dose therapy (3g oral powder) - Ideal for elderly patients with CKD
• Advantages:
  • Single-dose administration improves compliance
  • High urinary concentrations for days after a single dose
  • Excellent activity against most uropathogens including E. coli (95.5% susceptibility) 1
  • Minimal cross-reactivity with other antibiotic classes
  • No dosage adjustment needed in CKD stage II
  • Recommended by European guidelines for UTI 2

Amoxicillin-Clavulanate

• Dosing: 500mg/125mg twice daily
• Advantages:
  • Twice-daily dosing meets requirement
  • Good option for UTI when susceptibility is confirmed
  • 93% cure rate for susceptible isolates 3
  • Appropriate for CKD stage II with standard dosing

Alternative Options

Cephalexin

• Dosing: 500mg twice daily
• Considerations:
  • Twice-daily dosing meets requirement
  • Safe in CKD stage II
  • Requires careful monitoring in markedly impaired renal function 4
  • Second-line option per guidelines 5

Tigecycline

• Dosing: 100mg loading dose, then 50mg twice daily
• Considerations:
  • Meets twice-daily requirement
  • Recommended for complicated intra-abdominal infections due to resistant organisms 2
  • Not recommended for UTI as first-line therapy 2
  • Should be avoided for bloodstream infections and pneumonia 2

Special Considerations for This Patient

Age and Renal Function

• At 85 years with CKD stage II:
  • Avoid nephrotoxic agents
  • Fluoroquinolones should be used with caution due to increased risk of tendinopathy, CNS effects, and peripheral neuropathy in elderly patients 1
  • Aminoglycosides require careful monitoring despite their effectiveness in UTI 2

Empiric Treatment While Awaiting Culture Results

• Since culture sensitivity is pending:
  • Choose an antibiotic with broad coverage against common uropathogens
  • Consider local resistance patterns for E. coli
  • Avoid recent antibiotic exposures (especially fluoroquinolones, trimethoprim-sulfamethoxazole) due to increasing resistance 5

Monitoring and Follow-up

• Monitor renal function during treatment
• Assess clinical response within 48-72 hours
• Adjust therapy based on culture and sensitivity results when available
• Consider imaging studies if symptoms persist to rule out complications
• Complete treatment course (7-14 days for complicated UTI) 1

Pitfalls to Avoid

• Fluoroquinolones: Despite meeting dosing requirements, avoid as first-line due to risk of adverse effects in elderly and increasing resistance rates
• Trimethoprim-sulfamethoxazole: High resistance rates (69-75%) make it a poor empiric choice 6
• Nitrofurantoin: While effective for uncomplicated cystitis, it requires more frequent dosing (typically QID) and is contraindicated in moderate-severe renal impairment
• Underdosing antibiotics: Ensure adequate dosing despite renal impairment to achieve therapeutic concentrations

If the patient has risk factors for resistant organisms or previous treatment failure, consider hospitalization for IV therapy with agents like ceftazidime-avibactam or meropenem-vaborbactam while awaiting culture results 2.