What is the recommended dose of Diflucan (fluconazole) for a complicated urinary tract infection (UTI) with candidiasis?

Fluconazole Dosing for Complicated UTI with Candidiasis

For complicated urinary tract infections with candidiasis, oral fluconazole 200-400 mg (3-6 mg/kg) daily for 2 weeks is the recommended treatment regimen. 1

Dosing Algorithm

Initial Assessment

• Identify the Candida species if possible
• Determine fluconazole susceptibility
• Evaluate for urinary tract obstruction or foreign bodies (catheters, stents)

Standard Dosing Regimen

1. For fluconazole-susceptible organisms:

   • Loading dose: 200-400 mg (3-6 mg/kg) on day 1
   • Maintenance: 200-400 mg (3-6 mg/kg) daily for 2 weeks 1

2. For fluconazole-resistant C. glabrata:

   • Amphotericin B deoxycholate 0.3-0.6 mg/kg daily for 1-7 days with or without oral flucytosine (25 mg/kg 4 times daily) 1
   • Alternative: Oral flucytosine monotherapy, 25 mg/kg 4 times daily for 2 weeks 1

3. For C. krusei infections:

   • Amphotericin B deoxycholate 0.3-0.6 mg/kg daily for 1-7 days 1

Additional Management Considerations

Critical Interventions

• Eliminate urinary tract obstruction if present (strong recommendation) 1
• Remove or replace nephrostomy tubes or stents if feasible 1
• Remove indwelling bladder catheters if possible 1

For Refractory Cases

• For fluconazole-resistant species (C. glabrata, C. krusei): Consider amphotericin B deoxycholate bladder irrigation (50 mg/L sterile water daily for 5 days) 1
• For fungal balls or renal pelvis involvement: Irrigation through nephrostomy tubes with amphotericin B deoxycholate (25-50 mg in 200-500 mL sterile water) 1

Evidence Strength and Considerations

The Infectious Diseases Society of America (IDSA) guidelines provide strong recommendations for fluconazole dosing in complicated UTI with candidiasis, though based on low-quality evidence 1. This reflects the limited number of high-quality randomized controlled trials in this specific clinical scenario.

Recent pharmacokinetic research supports this dosing recommendation, noting that a 200 mg loading dose followed by 100-200 mg daily achieves adequate urinary concentrations 2. Fluconazole is particularly effective for urinary tract infections because it achieves high concentrations in the urine 3, 4.

Important Caveats

• Fluconazole is the preferred agent due to its safety profile and high urinary concentrations 4
• Echinocandins should be avoided for urinary tract infections as they do not achieve adequate urinary concentrations 4
• For patients with renal impairment, dose adjustment is necessary
• Treatment success rates of 85-90% have been reported with appropriate fluconazole dosing 5, 6
• Surgical intervention is strongly recommended for adults with fungal balls or abscesses 1

Remember that elimination of predisposing factors (catheters, obstruction) is as important as antifungal therapy for achieving clinical cure and preventing recurrence.