What is the appropriate treatment and dosage of fluconazole (an antifungal medication) for a patient with a suspected fungal urinary tract infection (UTI)?

Fluconazole Treatment for Fungal UTI

For symptomatic Candida cystitis caused by fluconazole-susceptible species, treat with oral fluconazole 200 mg daily for 14 days. 1

Clinical Decision Algorithm

Step 1: Determine if Treatment is Indicated

Asymptomatic candiduria does NOT require treatment in most patients 1. Treatment is only indicated for:

• High-risk patients: neutropenic patients, very low birth weight infants, or those undergoing urologic procedures 1
• Symptomatic patients: those with dysuria, frequency, urgency, or systemic signs 1
• Suspected disseminated candidiasis: treat as candidemia, not as isolated UTI 1

Step 2: Remove Predisposing Factors

Remove indwelling urinary catheters whenever possible - this alone resolves candiduria in approximately 50% of cases without antifungal therapy 2. Elimination of predisposing factors often results in spontaneous resolution 1.

Step 3: Identify the Site of Infection

For Symptomatic Cystitis (Lower UTI)

• Fluconazole 200 mg (3 mg/kg) orally daily for 14 days 1, 2
• This is the drug of first choice because fluconazole achieves high urinary concentrations in its active form and is highly effective against most Candida species 1

For Pyelonephritis (Upper UTI)

• Fluconazole 200-400 mg (3-6 mg/kg) orally daily for 14 days for fluconazole-susceptible organisms 1, 2
• If pyelonephritis is accompanied by suspected disseminated candidiasis, treat as candidemia with higher doses 1

Step 4: Consider Species-Specific Resistance

Critical caveat: Not all Candida species are fluconazole-susceptible 1:

• C. albicans and C. tropicalis: Usually fluconazole-susceptible; use standard dosing 1
• C. glabrata: Often fluconazole-resistant; use amphotericin B deoxycholate 0.3-0.6 mg/kg daily for 1-7 days OR flucytosine 25 mg/kg four times daily for 7-10 days 1, 2
• C. krusei: Inherently fluconazole-resistant; never use fluconazole - use amphotericin B deoxycholate instead 1, 2

Step 5: Adjust for Renal Impairment

For patients with creatinine clearance <45 mL/min/1.73 m²: Reduce the maintenance dose by 50% but maintain daily frequency 2, 3. For example, use 100 mg daily instead of 200 mg daily for cystitis.

For hemodialysis patients: Administer the full dose after each dialysis session (typically 3 times weekly) 2, 3.

Common Pitfalls to Avoid

• Do not treat asymptomatic candiduria unless the patient is high-risk (neutropenic, very low birth weight infant, or undergoing urologic manipulation) 1

• Do not use bladder irrigation with amphotericin B as primary therapy - it has high relapse rates and is only useful for refractory fluconazole-resistant organisms, particularly C. glabrata 1

• Do not use echinocandins or lipid formulations of amphotericin B for UTI - they do not achieve adequate urinary concentrations and are generally ineffective 1, 4

• Do not use other azoles (voriconazole, itraconazole, posaconazole) for UTI - they have minimal urinary excretion of active drug 1

• Monitor for treatment failure, particularly with C. glabrata infections, and obtain follow-up urine cultures if clinical improvement is not observed 2

Special Populations

Neonates: Use fluconazole 12 mg/kg daily for disseminated candidiasis, but this is reasonable for UTI only if not on fluconazole prophylaxis 1. Amphotericin B deoxycholate 1 mg/kg daily is preferred for neonates with systemic involvement 1.

Patients undergoing urologic procedures: Prophylactic fluconazole 200-400 mg (3-6 mg/kg) daily OR amphotericin B deoxycholate 0.3-0.6 mg/kg daily for several days before and after the procedure 1.

Alternative Dosing from Research

While guidelines recommend 200 mg daily, some research suggests a 200 mg loading dose followed by 100 mg daily for at least 4 days may be adequate for uncomplicated symptomatic cystitis 5. However, the guideline-recommended 200 mg daily for 14 days remains the standard of care 1, 2.