Is nystatin appropriate as a first‑line treatment for fungal eye infections such as keratitis or conjunctivitis?

Nystatin and Eye Problems

Nystatin is explicitly contraindicated for ophthalmic use and should never be used as first-line treatment for fungal eye infections such as keratitis or conjunctivitis. 1

FDA-Approved Indications and Critical Contraindication

• The FDA drug label for nystatin topical powder clearly states it is "not indicated for systemic, oral, intravaginal or ophthalmic use" despite being effective for cutaneous or mucocutaneous Candida infections. 1
• This absolute contraindication exists regardless of the causative fungal organism or severity of ocular infection. 1

Appropriate First-Line Antifungal Agents for Fungal Eye Infections

For Fungal Keratitis (Corneal Infections)

• Natamycin (pimaricin) is the recommended first-line topical agent for fungal keratitis, offering the widest antifungal spectrum with medium-level activity, and serves as appropriate prophylaxis while awaiting fungal identification and sensitivity testing. 2
• Topical administration is essential since it provides the best opportunity for achieving therapeutic corneal drug levels, with molecular weight being critical for corneal epithelial penetration. 3
• Early initiation of specific topical antifungal therapy is crucial for successful treatment outcomes and visual function preservation. 3

For Candida-Specific Ocular Infections

• Flucytosine combined with amphotericin B is the recommended treatment for Candida eye infections, including when Candida bloodstream infection leads to ocular complications. 2
• The Infectious Diseases Society of America guidelines support amphotericin B deoxycholate at 0.3–0.6 mg/kg daily for invasive Candida infections, though this primarily addresses systemic rather than isolated ocular disease. 4
• Any early antifungal treatment (particularly echinocandins in systemic candidemia) reduces the risk of endophthalmitis development. 5

For Other Filamentous Fungal Infections

• Clotrimazole is the drug of choice for Aspergillus species, though miconazole and econazole may be superior for certain isolates based on sensitivity testing. 2
• Miconazole and econazole are recommended for miscellaneous filamentous fungi, with treatment guided by antifungal sensitivity results. 2
• For Fusarium infections not responding to natamycin, alternative agents (clotrimazole, miconazole, econazole, or thiabendazole) should be selected based on sensitivity testing. 2

Critical Treatment Principles for Fungal Eye Infections

Diagnostic Requirements

• Clinical suspicion of fungal etiology must prompt immediate collection of corneal smears and cultures to identify the organism, as rapid diagnosis is essential for preserving visual function. 3
• Fungal keratitis must be definitively ruled out before initiating any corticosteroid therapy, as steroid use is a documented risk factor for requiring penetrating keratoplasty in fungal infections. 4, 6

Route of Administration Strategy

• Topical antifungal therapy is the primary treatment modality for fungal keratitis since it achieves the highest corneal drug concentrations. 3, 2
• Systemic antifungal administration may be necessary for resistant fungal corneal ulcers that fail topical therapy alone. 3
• For fungal endophthalmitis, combined topical, systemic, and possibly intraocular antifungal therapy is required to preserve vision and eliminate the pathogen. 3

Duration and Monitoring

• Effective antifungal therapy must be long-term, nondamaging to ocular tissues, capable of penetrating the eye, and highly active against the specific fungal pathogen. 2
• Treatment should continue until complete eradication is confirmed, with some cases requiring excisional keratoplasty combined with lens removal and evacuation of posterior chamber contents. 2

Common Pitfalls to Avoid

• Never use nystatin for any ophthalmic indication, as it lacks FDA approval and appropriate formulation for ocular use. 1
• Do not delay antifungal treatment while awaiting culture results; begin empiric therapy with natamycin immediately upon clinical suspicion. 2
• Avoid initiating corticosteroids in any case where fungal infection has not been excluded, as this dramatically worsens outcomes. 4, 6
• Do not rely on systemic antifungal therapy alone for corneal infections, as topical administration is essential for achieving therapeutic drug levels in the cornea. 3

Historical Context

• While one 1990 case report described successful treatment of Candida conjunctivitis with nystatin ointment and oral tablets, this predates current FDA labeling restrictions and does not represent contemporary standard of care. 7
• Modern antifungal agents (azole derivatives and polyenes like amphotericin B and natamycin) have superior pharmacokinetic profiles and are the current agents of choice. 3