Topical antifungal (ophthalmic — polyene) Pregnancy: Use only if clearly needed — limited data; systemic absorption negligible.

Natamycin 5% Eye Drops

Brand names: Natacyn

Adult dose

Dose: 1 drop every 1–2 hours for first 3–4 days (intensive), then 6–8 times daily for 3–4 weeks

Route: Ophthalmic

Frequency: Hourly initially, reducing to 6–8 times daily

Max: 1 drop per application; frequency per protocol

Fungal keratitis (filamentous fungi — Fusarium, Aspergillus): intensive hourly dosing for 3–4 days, then 6–8x/day continuing for minimum 3 weeks or until resolution confirmed by clinical/microbiological cure. Shake suspension before use. Specialist/tertiary centre management. Concurrent systemic antifungal (voriconazole) often required for deep or severe infections.

Paediatric dose

Route: Ophthalmic

Frequency: As per adult protocol

Max: Same as adult

Used in children under specialist supervision. Same dosing as adults. Rare in children (typically associated with agricultural trauma or immunocompromise).

Dose adjustments

Renal

No adjustment required — minimal systemic absorption.

Hepatic

No adjustment required.

Clinical pearls

Drug of choice for Fusarium keratitis (most common filamentous fungal keratitis in UK)
Candida keratitis responds better to topical voriconazole or amphotericin B than natamycin
Microbiological confirmation (corneal scraping + culture) before starting — clinical diagnosis of fungal keratitis is unreliable
Treatment course is prolonged (minimum 3 weeks) — non-adherence is a major cause of failure
Suspect fungal keratitis in: contact lens wearers, agricultural workers, immunocompromised, steroid use on pre-existing corneal infection

Contraindications

Hypersensitivity to natamycin or polyene antifungals
Viral or bacterial keratitis without antifungal confirmation (misdiagnosis risk)

Side effects

Ocular discomfort, stinging, and irritation
Conjunctival chemosis and hyperaemia
Corneal epithelial toxicity (with prolonged intensive use)
White suspension residue on eye surface (resolves with blinking)

Interactions

Avoid concurrent topical steroids — steroids worsen fungal keratitis

Monitoring

Slit lamp at 48–72 hours and weekly
Corneal scraping repeat culture if not responding
Specialist review

Reference: BNFc; BNF; RCOphth Microbial Keratitis Guidelines; Natacyn SPC. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Pathways