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Idoxuridine Ophthalmic

By Rania Gollakner, BS, DVM, MPH


What is idoxuridine?

Idoxuridine (brand name Dendrid®, Herplex®) is an antiviral topical medication used to treat viral infections of the eye, such as herpesvirus-1 in cats.

When idoxuridine is prescribed in the treatment of herpesvirus in cats, it is referred to as ‘extra-label’ or ‘off label’ use. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully, as their directions may be significantly different from those on the label.

How do I give my pet idoxuridine?eyedrops_cat

Idoxuridine comes as eye drops, or can be compounded by your veterinarian into an eye ointment. Your veterinarian will provide specific instructions for your cat. It is important that you administer this drug to your cat’s eye in the exact amount that it has been prescribed. Drops usually need to be applied every few hours for the first 48 hours, and then several times a day for a week beyond your cat’s clinical signs clearing up.

Wait 5-10 minutes before applying any other medications to the eye.

It is important to avoid contamination of the eye medication’s applicator tip. Wear disposable gloves when handling this medication. For tips and instructions on administering eye drops and eye ointments, see handouts “Applying Eye Drops to Cats” and “Applying Eye Ointments to Cats”.

What if I miss giving my pet the medication?

If you miss giving your pet a dose, give the next dose as soon as you remember, but if it is close to the next scheduled dose when you remember, skip the missed dose and give it at the next scheduled time and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Side effects of idoxuridine include eye irritation. The irritation caused by the administration of the drug may be more intense than the inflammation caused by the herpesvirus. Prolonged use can cause other eye conditions.

Any side effects that you observe should be reported to your veterinarian.

Are there any risk factors for this medication?

Idoxuridine should not be used in patients with hypersensitivity to the drug. This medication should be used with caution in animals that are pregnant or nursing. This drug can cause serious adverse effects in people or animals. The drug can be found in the treated cat’s saliva, urine, or feces. Use disposable gloves when handling this medication, and disposing of cat litter. Do not let treated animals lick human skin. Contact your family physician if any exposure to this medication occurs. Pregnant women should NOT handle this medication.


Are there any drug interactions I should be aware of?

Other drugs can interact with this medication, so be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.


Is there any monitoring that needs to be done with this medication?

Your veterinarian may monitor your cat to ensure that the infection has cleared.

How do I store idoxuridine?

Store idoxuridine the refrigerator away from moisture and sunlight. Do not allow the medication to freeze.

What should I do in case of emergency?

An overdose of eye medication is unlikely, but side effects or toxic effects could occur if you cat eats the medication. If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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