Antifungal — Topical Ophthalmic (Polyene) Pregnancy: Limited data — minimal systemic absorption; considered low risk for topical use

Natamycin 5% Eye Drops

Brand names: Natacyn

Adult dose

Dose: 1 drop every 1–2 hours initially (severe fungal keratitis), then reduce to 1 drop every 4–6 hours as response improves

Route: Topical (ophthalmic)

Frequency: Hourly initially; reducing as response achieved

Max: 1 drop every hour (acute phase)

Treatment of fungal keratitis (filamentous fungi — Aspergillus, Fusarium; and yeasts — Candida). Minimum 14–21 day treatment; often 6–8 weeks. Must be shaken well before use — suspension. Requires urgent ophthalmology referral — fungal keratitis is sight-threatening.

Paediatric dose

Route: Topical

Frequency: Every 2–4 hours

Max: Same as adult

Paediatric fungal keratitis — under specialist guidance

Dose adjustments

Renal

No adjustment — topical; negligible systemic absorption

Hepatic

No adjustment

Clinical pearls

MUTT trial (NEJM 2012): natamycin superior to voriconazole for filamentous fungal keratitis (especially Fusarium) — visual outcomes significantly better with natamycin; changed practice toward natamycin first-line for filamentous fungi
Candida keratitis: voriconazole or amphotericin B may be preferred for Candida (yeast) keratitis over natamycin — natamycin shows variable activity against Candida
Fungal keratitis risk factors: corneal trauma with vegetable matter (agricultural injury), contact lens wear, prolonged topical steroid use, immunocompromised state — always consider fungal aetiology in these contexts; bacterial culture alone will miss fungi
Corneal scraping culture is MANDATORY before starting antifungal therapy — fungal keratitis is diagnosed by culture (Sabouraud's medium), KOH staining, and in vivo confocal microscopy; empirical treatment without diagnosis is inappropriate for severe keratitis
Do not use corticosteroids concurrently — topical steroids worsen fungal keratitis by suppressing immune response; if already prescribed, must be stopped immediately

Contraindications

Hypersensitivity to natamycin
Bacterial keratitis (not appropriate treatment)

Side effects

Local irritation and burning
Conjunctival hyperaemia
Oedema
Foreign body sensation

Interactions

No clinically significant drug interactions at topical doses

Monitoring

Slit-lamp examination — infiltrate size and density at 1 week
Culture results at 5–7 days (sensitivity-guided therapy adjustment)
Visual acuity
IOP (may rise with inflammatory response)

Reference: BNFc; BNF 90; MUTT Trial (NEJM 2012); RCOphth Microbial Keratitis Guidelines; AAO Fungal Keratitis PPP; SPC Natacyn. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Pathways