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Corneal penetration of topical amphotericin B and natamycin
Abstract:
The corneal uptake and penetration of 14C-labelled 0.15% amphotericin B and 5% natamycin were studied in Dutch-belted rabbits. Corneal levels of natamycin were substantially higher than amphotericin B. For both drugs, these levels were influenced by corneal contact time. In corneas debrided of epithelium, both agents entered the corneal stroma and levels were detected in aqueous in the therapeutic range. However, in corneas with intact epithelium, penetration was negligible for amphotericin B (0.23 microgram/gm at 2 mins). By contrast, although penetration of natamycin was greatly reduced, 7.0 micrograms/gm were present at 2 mins.
Insights
This study compared corneal penetration of amphotericin B and natamycin in rabbits. Natamycin showed significantly higher corneal levels than amphotericin B, especially with intact corneas, suggesting better topical efficacy.
Area of Science:
- Ophthalmology
- Pharmacology
- Drug Delivery
Background:
- Ocular fungal infections require effective topical antifungal agents.
- Corneal penetration is critical for the efficacy of topical ophthalmic drugs.
- Amphotericin B and natamycin are used to treat fungal keratitis.
Purpose of the Study:
- To compare the corneal uptake and penetration of 0.15% amphotericin B and 5% natamycin in Dutch-belted rabbits.
- To evaluate the influence of corneal contact time on drug levels.
- To assess penetration through intact and debrided corneal epithelium.
Main Methods:
- Dutch-belted rabbits were treated with 14C-labelled amphotericin B (0.15%) and natamycin (5%).
- Corneal and aqueous humor drug concentrations were measured.
- Penetration was assessed in corneas with intact and debrided epithelium.
Main Results:
- Corneal levels of natamycin were substantially higher than amphotericin B.
- Both drugs' corneal levels were influenced by contact time.
- In debrided corneas, both agents reached therapeutic levels in the aqueous humor.
- In intact corneas, amphotericin B penetration was negligible (0.23 µg/gm at 2 min), while natamycin penetration was reduced but significant (7.0 µg/gm at 2 min).
Conclusions:
- Natamycin demonstrates superior corneal penetration compared to amphotericin B, particularly in the presence of an intact corneal epithelium.
- These findings suggest natamycin may offer better therapeutic potential for topical treatment of fungal keratitis.
- Drug penetration is significantly influenced by the integrity of the corneal epithelial barrier.