What is the best course of action for a 57-year-old patient with frequent urination, positive leucocytes, and trace protein in urine, who is already taking nitrofurantoin (antimicrobial) 100mg modified release as prophylaxis?

Management of UTI in a Patient on Nitrofurantoin Prophylaxis

For a 57-year-old patient with increased urinary frequency, positive leukocytes and trace protein on urinalysis, who is already on nitrofurantoin 100mg modified release prophylaxis, a different antibiotic should be prescribed to treat the current infection.

Assessment of Current Situation

• The patient presents with increased urinary frequency without dysuria, positive leukocytes and trace protein on urinalysis, suggesting a breakthrough urinary tract infection despite being on nitrofurantoin prophylaxis 1
• The absence of fever or other systemic symptoms indicates this is likely an uncomplicated lower UTI rather than pyelonephritis 1
• Breakthrough infection while on prophylactic nitrofurantoin suggests the possibility of resistant organisms 2

Treatment Recommendation

First-line Treatment Options:

• Fosfomycin trometamol 3g single dose is recommended as the most appropriate treatment option 1

  • Provides a different mechanism of action than the current prophylactic agent
  • Single-dose therapy improves compliance
  • Effective against many nitrofurantoin-resistant organisms

• Alternative options include:

  • Trimethoprim-sulfamethoxazole 160/800mg twice daily for 3 days (if local resistance patterns permit) 1
  • Cephalosporins (e.g., cefadroxil 500mg twice daily for 3 days) if local E. coli resistance is <20% 1

Avoid:

• Additional nitrofurantoin therapy, as the breakthrough infection suggests resistance to the current prophylactic regimen 2, 3
• Fluoroquinolones should be reserved for more severe infections due to concerns about resistance and adverse effects 1

Follow-up Plan

• Urine culture should be obtained before starting new antibiotics to guide therapy if symptoms don't resolve 1
• If symptoms do not resolve within 4 weeks of treatment completion or recur within 2 weeks, perform urine culture with antimicrobial susceptibility testing 1
• Consider reevaluating the effectiveness of the current prophylactic regimen after treating the acute infection 1

Prophylaxis Considerations

• After treating the current infection, evaluate whether continuing nitrofurantoin prophylaxis is appropriate 1, 4
• Consider alternatives if breakthrough infections continue:
  • Immunoactive prophylaxis 1
  • For postmenopausal women, vaginal estrogen replacement 1
  • Increased fluid intake may help reduce recurrent UTI risk 1

Important Caveats

• Nitrofurantoin is contraindicated in patients with creatinine clearance <60 mL/min due to inadequate urinary drug concentrations and increased toxicity risk 4
• Patients on long-term nitrofurantoin prophylaxis may develop infections with resistant organisms, particularly Klebsiella and Pseudomonas species 2
• The European Association of Urology recommends not performing extensive workup (cystoscopy, abdominal ultrasound) in women younger than 40 with recurrent UTI without risk factors 1