What is the recommended dosage of Nystatin (antifungal medication) for a patient with a fungal infection, specifically oral thrush or intestinal candidiasis?

Nystatin Dosage for Oral Thrush and Candidiasis

For mild oral thrush, use nystatin suspension 4-6 mL (400,000-600,000 units) four times daily for 7-14 days, but for moderate-to-severe disease or immunocompromised patients, fluconazole 100-200 mg daily is superior and should be used instead. 1, 2

Specific Dosing by Age and Formulation

Infants

• Nystatin suspension: 2 mL (200,000 units) four times daily 3
• Use dropper to place half the dose in each side of mouth 3
• Avoid feeding for 5-10 minutes after administration 3
• For premature and low birth weight infants: 1 mL four times daily is effective 3

Children and Adults

• Nystatin suspension: 4-6 mL (400,000-600,000 units) four times daily 1, 3
• Place half the dose in each side of mouth 3
• Retain in mouth as long as possible (at least 2 minutes) before swallowing 2
• Swallow rather than spit to treat potential esophageal involvement 2

Alternative Formulation

• Nystatin pastilles: 1-2 pastilles (200,000 units each) four times daily for 7-14 days 1, 2
• Allow pastilles to dissolve slowly in the mouth 1
• Higher doses (400,000 IU) achieve better mycological cure rates than 200,000 IU 4

Treatment Duration and Timing

• Standard duration: 7-14 days 1, 2
• Continue for at least 48 hours after symptoms disappear and cultures confirm Candida eradication 2, 3
• Administer ideally after meals and before bedtime 2
• Treatment for 4 weeks may be more effective than 2 weeks for resistant cases 4

When Nystatin is NOT Appropriate

Use Fluconazole Instead for:

• Moderate-to-severe oral candidiasis: fluconazole 100-200 mg daily for 7-14 days 1, 2
• Immunocompromised patients (HIV/AIDS, transplant recipients, chemotherapy patients) 2
• Treatment failure after 7 days of nystatin 1

Critical caveat: Nystatin has significantly lower efficacy than fluconazole, with clinical cure rates of only 32-54% compared to 100% with fluconazole in infants 2, 5. In immunocompromised children, nystatin achieves only 51% clinical cure versus 91% with fluconazole 6.

Enhanced Efficacy Strategy

Combination therapy with suspension plus pastilles achieves higher cure rates than suspension alone 2, 4:

• Nystatin suspension 4-6 mL four times daily PLUS
• Nystatin pastilles 1-2 pastilles four times daily
• Continue for 7-14 days 2

Special Considerations

Denture-Related Candidiasis

• Denture disinfection is mandatory in addition to antifungal therapy 1, 2
• Nystatin alone without denture treatment will fail 1

HIV-Infected Patients

• Antiretroviral therapy is more important than antifungal choice for preventing recurrence 2
• For recurrent infections: fluconazole 100 mg three times weekly for chronic suppression 2

Treatment Failure Algorithm

If no improvement after 7 days 1:

1. Confirm diagnosis with culture
2. Switch to itraconazole solution 200 mg once daily (effective in two-thirds of fluconazole-refractory cases) 2
3. Alternative options: posaconazole suspension 400 mg twice daily for 3 days then 400 mg daily, or voriconazole 200 mg twice daily 2
4. Last resort: IV amphotericin B 0.3 mg/kg daily 2

Intestinal Candidiasis

Nystatin is NOT absorbed systemically and is only appropriate for prophylaxis in very high-risk patients 7:

• Limited to leukemic patients during chemotherapy 7
• For invasive or systemic candidiasis, systemic antifungals (fluconazole, echinocandins, or amphotericin B) are required 7, 1

Common Pitfalls to Avoid

• Do not use nystatin for esophageal candidiasis—systemic therapy is required 2
• Do not use nystatin as first-line for moderate-to-severe disease 1, 2
• Poor taste and gastrointestinal adverse effects are common and may reduce adherence 4
• Relapse rates are higher with nystatin compared to azoles 8