NATAMYCIN (OPHTHALMIC)

Indications/Pharmacology

Natamycin is a semisynthetic polyene antibiotic. Natamycin is poorly watersoluble and will not penetrate the intact corneal epithelium. Natamycin is the only antifungal agentapproved for use on the eye and the only commercially available eye drug for treatment of fungalkeratitis.Suggested Dosages/Precautions/Adverse Effects - The product comes as a thick white suspensionwhich complicates the use of subpalpebral lavage apparatus for frequent treatment of the cornea of thehorse. The drug tends to plug up the tubing systems used for medication. It will cause dramatic swellingand pain in the upper eyelid if it leaks out of the tubing into the subcutaneous tissues of the eyelid.
Corneal penetration is poor and the medication is very expensive. Fungal keratitis cases are treatedaggressively with hourly or bi-hourly treatment the first 1 to 3 days and gradual reduction in treatmentfrequency with signs of clinical improvement. Cytology and repeated cultures of the cornea are used toindicate treatment effectiveness. Worsening of the corneal edema and cellular infiltration can be a sign oftreatment response. This is thought to be due to antigenic release associated with killing of fungalorganisms (like the pulmonary response noted in dogs with institution of antifungal therapy forblastomycosis, etc.). Four to six weeks of treatment is not uncommon for fungal keratitis cases.Dosage Forms/Preparations/FDA Approval Status - Veterinary-Approved Products: None

Human-Approved Products:

Natamycin Ophthalmic Suspension 5% in 15 ml btls Natacyn® (Alcon); (Rx)