What is the appropriate dosage and treatment duration for prescribing fluconazole to a patient with a fungal infection, considering factors such as infection severity and renal function?

How to Prescribe Fluconazole

Fluconazole dosing depends critically on the infection site and severity, ranging from a single 150 mg dose for uncomplicated vaginal candidiasis to 400 mg daily for invasive infections, with treatment duration varying from one day to 3-6 months based on clinical response and infection type. 1, 2, 3

Mucocutaneous Infections

Vulvovaginal Candidiasis

• Uncomplicated cases: Single dose of fluconazole 150 mg orally achieves >90% clinical cure rates 1, 4
• For recurrent vulvovaginal candidiasis (≥4 episodes/year): Fluconazole 150 mg weekly for 6 months reduces recurrence from 64% to 9% 1
• Short-course oral azole therapy should be avoided in HIV-positive patients, though topical agents remain effective 5

Oropharyngeal Candidiasis

• Mild disease: Fluconazole 100-200 mg daily for 7-14 days 1, 2, 3
• Pediatric dosing: 6 mg/kg loading dose on day 1, then 3 mg/kg daily for at least 2 weeks 3
• In HIV patients with CD4 <150 cells/μL and frequent relapses: Consider maintenance therapy with fluconazole 100-200 mg three times weekly (though daily dosing is preferred) 5

Esophageal Candidiasis

• Standard regimen: Fluconazole 200-400 mg (3-6 mg/kg) daily for 14-21 days until clinical improvement 5, 2
• Pediatric dosing: 6 mg/kg loading dose, then 3 mg/kg daily (up to 12 mg/kg/day based on response) for minimum 3 weeks and at least 2 weeks after symptom resolution 3
• For azole-refractory disease in HIV patients: Consider echinocandins (micafungin 150 mg/day or anidulafungin) or amphotericin B formulations 5

Urinary Tract Infections

Asymptomatic Candiduria

• Treatment NOT recommended in immunocompetent patients 5, 1
• Exception: High-risk surgical patients, neonates, or neutropenic patients should be treated as disseminated candidiasis 5
• For patients undergoing urologic procedures: Treat with fluconazole before and after the procedure 5

Symptomatic Cystitis

• Fluconazole 200 mg (3 mg/kg) daily for 14 days 5, 2
• Critical pitfall: Remove indwelling bladder catheters, as continuing catheters significantly reduces cure rates 1

Pyelonephritis

• Fluconazole 200-400 mg (3-6 mg/kg) daily for 14 days 5, 2
• If pyelonephritis with suspected disseminated candidiasis: Treat as candidemia 5

Invasive Candidiasis

Candidemia (Non-Neutropenic Patients)

• Fluconazole 400-800 mg loading dose, then 400 mg daily 1
• Duration: Continue for 2 weeks AFTER first negative blood culture and resolution of symptoms, not from start of therapy 5, 2
• Pediatric dosing: 6-12 mg/kg/day 3

Chronic Disseminated Candidiasis

• Fluconazole at standard doses continued until lesions completely resolve, typically 3-6 months 5, 2
• Fluconazole can be used as step-down therapy in stable patients 5

CNS Candidiasis

• Fluconazole 400-800 mg (6-12 mg/kg) daily for patients unable to tolerate amphotericin B 5
• Remove intraventricular devices 5
• Treat until all signs, symptoms, CSF abnormalities, and radiologic findings resolve 5
• Pediatric dosing: 12 mg/kg loading dose, then 6-12 mg/kg daily based on response 3

Candida Endophthalmitis

• Fluconazole as alternative to amphotericin B 5
• Duration: At least 4-6 weeks, determined by repeated examinations to verify resolution 5

Special Populations

Neonates

• Fluconazole 12 mg/kg/day for 3 weeks (if no persistent fungemia or metastatic complications) 5, 2
• Premature newborns (gestational age 26-29 weeks): Same mg/kg dose but administered every 72 hours for first 2 weeks of life, then once daily 3
• Perform lumbar puncture and ophthalmoscopic examination in neonates with positive sterile body fluid/urine cultures 5

Neutropenic Patients

• Prophylaxis: Fluconazole 400 mg daily during chemotherapy-induced neutropenia, continuing throughout period of neutropenia risk 1

Bone Marrow Transplant Recipients

• Prophylaxis: Fluconazole 400 mg daily starting several days before anticipated neutropenia, continuing for 7 days after neutrophil count >1000 cells/mm³ 1, 3

ICU Patients

• Consider fluconazole 800 mg loading dose, then 400 mg daily ONLY in units with high invasive candidiasis incidence (>5%) 1, 2

HIV/AIDS Patients

• For cryptococcal meningitis suppression: Fluconazole 200 mg once daily 3
• Pediatric cryptococcal meningitis: 12 mg/kg loading dose, then 6 mg/kg daily (up to 12 mg/kg based on response) for 10-12 weeks after CSF culture-negative 3
• Maintenance therapy generally NOT recommended unless relapses are frequent/severe and HAART is optimized 5

Renal Impairment Dosing

Loading dose remains unchanged (50-400 mg based on indication), then adjust maintenance dose: 3

• Creatinine clearance >50 mL/min: 100% of standard dose
• Creatinine clearance ≤50 mL/min (no dialysis): 50% of standard dose
• Hemodialysis: 100% of recommended dose after each dialysis session; on non-dialysis days, use reduced dose per creatinine clearance

Pediatric renal impairment: Dosage reduction should parallel adult recommendations, using estimated creatinine clearance (K × height in cm / serum creatinine, where K=0.55 for children >1 year, 0.45 for infants) 3

Critical Pitfalls to Avoid

• Do NOT use fluconazole prophylaxis routinely in immunocompetent patients taking antibiotics—this promotes resistance without proven benefit 1
• Do NOT discontinue therapy prematurely based solely on symptom resolution; complete the full recommended duration to prevent relapse 2
• Monitor for resistance, particularly with C. glabrata, which may develop fluconazole resistance during therapy requiring switch to amphotericin B deoxycholate 0.3-0.6 mg/kg daily 1
• C. krusei is intrinsically fluconazole-resistant; use alternative therapy (amphotericin B or echinocandins) 2
• Maximum daily dose is 1600 mg to avoid neurological toxicity 6
• Fluconazole is contraindicated in pregnancy 5