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Action/Kinetics:
Resembles thymidine; inhibits thymidylic phosphorylase and specific DNA polymerases required for incorporation of thymidine into viral DNA. Idoxuridine, instead of thymidine, is incorporated into viral DNA, resulting in faulty DNA and the inability of the virus to infect tissue or reproduce. May also be incorporated into mammalian cells. Does not penetrate the cornea well. Rapidly inactivated by nucleotidases or deaminases.
Uses:
Herpes simplex keratitis, especially for initial epithelial infections characterized by the presence of thread-like extensions.
NOTE: Idoxuridine will control infection but will not prevent scarring, loss of vision, or vascularization. Alternative form of therapy must be instituted if no improvement is noted after 7 days or if complete reepithelialization fails to occur after 21 days of therapy.
Contraindications:
Hypersensitivity; deep ulcerations involving stromal layers of cornea. Lactation. Concomitant use of corticosteroids in herpes simplex keratitis (corticosteroids may accelerate the spread of the viral infection).
Special Concerns:
May be sensitizing, especially with dermal use. Safety and efficacy have not been determined in children.
Side Effects:
Localized to eye. Temporary visual haze, irritation, pain, pruritus, inflammation, sensitivity to bright light, follicular conjunctivitis with preauricular adenopathy, mild edema of eyelids and cornea, allergic reactions (rare), photosensitivity, corneal clouding and stippling, small punctate defects.
NOTE: Squamous cell carcinoma has been reported at the site of application.
Overdose Management:
Symptoms (frequent administration): Defects on corneal epithelium.
Treatment: If an excess amount of drug is instilled in the eye, flush with water or normal saline.
Drug Interactions:
Concurrent use of boric acid may cause irritation.
How Supplied:
Solution: 0.1%
Dosage
?Ophthalmic (0.1%) Solution.
Initially: 1 gtt every hour during the day and q 2 hr during the night until definite improvement is noted (usually within 7 days).
Following improvement: 1 gtt q 2 hr during the day and q 4 hr at night. Continue for 3-7 days after healing is complete. Alternate dosing schedule: 1 gtt q min for 5 min; repeat q 4 hr, day and night.
