Basic Information
Edetate Disodium (sodium EDTA) is a chelating agent that is used in the treatment of corneal ulcers. Keratomalacia, or corneal melting, is the rapid degeneration of collagen and other components of the stoma of the cornea, which can lead to perforation of the cornea. This type of corneal ulcer usually has a grayish mucoid or gelatinous appearance around the ulcer margin. Sodium EDTA blocks the melting effects of collagenases and proteinases.
Bacterial pathogens, such as Pseudomonas and beta hemolytic Streptococcus, and some fungal pathogens are the most-common pathogens associated with corneal melting. A variety of factors contribute to destruction of the cornea, including the upregulation of cytokines in the tear film in response to infection, and the production of proteolytic enzymes by corneal epithelial cells, white blood cells, and the pathogenic organism. There are two groups of proteinases that affect the corneal matrix: metalloproteinase and serine proteinase. Sodium EDTA specifically inhibits matrix metalloproteinase.
Sodium EDTA should be administered every one - two hours. It may be used with other antiproteolytics such as, autologous serum, and acetylcysteine.
Dogs and Cats
Pseudomonas is the most-common organism associated with corneal melting in dogs and cats. Fungal infections are uncommon in dogs and cats.
Horses
Common causes of corneal ulceration in the horse are Staphylococcus, Streptococcus, Pseudomonas, Aspergillus, and Fusarium spp. Within this group, Streptococcus, Pseudomonas and the fungi have been implicated as a cause of melting corneal ulceration. Appropriate and aggressive treatment with antibiotics, antifungals, antiproteolytics such as edetate disodium, atropine, and systemic non-steroidal anti-inflammatory drugs may be necessary to halt the progression. Matrix metalloproteinases (sodium EDTA responsive) are the predominant proteinase in the horse. Because of the necessity for frequent treatment, many veterinary ophthalmologists recommend a nasolacrimal catheter, or a subconjunctival catheter.
Side Effects
No specific side-effects noted.
Precautions
Even with comprehensive medical treatment, melting corneal ulcers can progress very rapidly to full corneal perforation.
Drug Interactions
Corticosteroids should not be used in severe corneal ulcers.
Topical anesthetics, while appropriate for diagnostic purposes, should not be used during treatment due to toxicity to corneal epithelium.
Overdose
Sodium EDTA is used very frequently during the initial therapy of severe melting corneal ulceration. Overdose is not a concern.