What is nystatin used for and what is the recommended dosage?

What is Nystatin and Its Clinical Uses

Nystatin is a polyene antifungal agent used primarily for topical treatment of mucocutaneous candidiasis, including oropharyngeal candidiasis, vulvovaginal candidiasis, and prophylaxis of invasive candidiasis in high-risk neonates.

Primary Indications and Dosing

Oropharyngeal Candidiasis

For mild oropharyngeal candidiasis, nystatin suspension (100,000 U/mL) 4–6 mL four times daily OR nystatin pastilles (200,000 U each) 1–2 pastilles four times daily for 7–14 days is recommended 1.

• Alternative formulations include nystatin suspension at 200,000–400,000 U orally four times daily for 7–14 days (1–7 days in children) for uncomplicated disease 1.
• Nystatin pastilles demonstrate superior efficacy compared to suspension alone, with higher mycological cure rates when used at 400,000 IU versus 200,000 IU 2.
• Combination therapy using both pastilles and suspension for 2 weeks may achieve higher clinical and mycological cure rates than suspension alone 2.
• Treatment duration of 4 weeks with pastilles appears more effective than 2-week regimens 2.

Important caveat: Nystatin is less effective than azole antifungals for oropharyngeal candidiasis. Topically applied azole drugs are more effective than nystatin for treating vulvovaginal candidiasis 1.

Vulvovaginal Candidiasis

For uncomplicated vulvovaginal candidiasis, nystatin 100,000-unit vaginal tablet once daily for 14 days is an option, though topical azoles are preferred 1.

• For C. glabrata vulvovaginitis unresponsive to oral azoles, nystatin intravaginal suppositories 100,000 units daily for 14 days is an alternative 1.
• Nystatin is considered less effective than azole preparations, which achieve 80–90% symptom relief and negative cultures 1.

Neonatal Prophylaxis

For prevention of invasive candidiasis in extremely low birth weight neonates (<1500 g), oral nystatin 100,000 units three times daily for 6 weeks is recommended when fluconazole availability or resistance precludes its use 1.

• This recommendation applies specifically to nurseries where fluconazole cannot be used due to availability or resistance concerns 1.
• **Fluconazole prophylaxis (3–6 mg/kg twice weekly) is strongly preferred over nystatin for neonates <1000 g in high-risk nurseries** (>10% invasive candidiasis rate) 1.
• Nystatin prophylaxis has demonstrated efficacy in reducing invasive candidiasis in preterm infants <1500 g, with one study showing reduced all-cause mortality 1.
• Critical limitation: Nystatin cannot be administered during ileus, gastrointestinal disease, feeding intolerance, or hemodynamic instability—common situations in premature infants that limit its broad applicability 1.
• Evidence for nystatin efficacy in infants <750 g (highest risk group) remains limited 1.

Mechanism and Spectrum

• Nystatin is a non-absorbable polyene antifungal that works topically in the gastrointestinal tract and on mucosal surfaces 1, 3, 4.
• It demonstrates activity against various Candida species, though post-antifungal effects vary significantly: C. albicans shows the shortest effect (6.85 hours) while C. parapsilosis shows the longest (15.17 hours) 5.
• This variation in post-antifungal effect may explain persistent C. albicans infections despite adequate nystatin regimens 5.

Safety Considerations

• Most common adverse effects include poor taste and gastrointestinal reactions 2.
• Some commercial formulations contain sugar and ethanol, which can cause side effects; sugar-free and alcohol-free alternatives should be considered, especially for diabetic or geriatric patients 4.
• Nystatin is extremely toxic when administered systemically and is therefore restricted to topical/oral use only 3, 6.
• Potential concern exists for inadvertent damage to fragile gut epithelium in premature infants, possibly leading to necrotizing enterocolitis 1.

Clinical Positioning

Nystatin serves as a second-line or alternative agent in most scenarios:

• For oropharyngeal candidiasis, fluconazole (100–200 mg daily) is preferred for moderate to severe disease 1.
• For vulvovaginal candidiasis, topical azoles or single-dose oral fluconazole 150 mg are first-line 1.
• For neonatal prophylaxis, fluconazole is strongly preferred when available and appropriate 1.
• Nystatin remains valuable when azole resistance is present (particularly C. glabrata), when systemic absorption must be avoided, or when cost/availability favors its use 1, 4.