Idoxuridine Ophthalmic

What is idoxuridine?

Idoxuridine (brand names Dendrid®, Herplex®, Stoxil®) is an antiviral topical medication used to treat viral infections of the eye, such as feline herpesvirus-1 (FHV-1) in cats. It may also be useful for treating canine herpesvirus-1 in dogs and equine herpesvirus-2 in horses.

When idoxuridine is prescribed for the treatment of herpesvirus in cats, dogs, and horses, it is referred to as off label (extra label). Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How do I give my pet idoxuridine?

• Idoxuridine comes as eye drops or can be compounded by your veterinarian into an eye ointment. In the United States, idoxuridine must be compounded as it is no longer commercially available. 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 it has been prescribed.  
• Do not give this medication if the solution becomes cloudy or if it appears to contain particulate matter. 
• Drops usually must be applied every few hours for the first 48 hours, and then several times a day, and for a week after your cat’s clinical signs clear up.
• Wait 5-10 minutes before applying any other medications to the eye.
• Do not touch your cat's eye with the dropper tip and keep a tight lid on the bottle when not in use.
• Use disposable gloves when handling this medication and when disposing of cat litter. If your pet vomits after giving this drug, wear gloves while cleaning up.
• Dispose of used gloves in the trash immediately after use.
• Avoid any contact with your skin, eyes, or mucous membranes.
• Do not let treated animals lick human skin. 
• DO NOT handle this medication if you are pregnant.

Idoxuridine can cause serious adverse effects in people and animals, so it is essential to avoid accidental exposure. The drug can be found in the treated cat’s saliva, urine, or feces. Contact your family physician if any exposure to this medication occurs.

This medication can take a few weeks before full effects are noted, but gradual improvements are usually noticeable after a few days.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.

Are there any potential side effects?

Idoxuridine may cause the following side effects:

• Eye irritation, such as a burning sensation (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

If any of the following signs develop, inform your veterinarian immediately:

• Eye cloudiness
• Stippling (dotted appearance on the retina)
• Swelling

Serious adverse reactions may occur. If any of the following signs develop, stop giving idoxuridine and contact your veterinarian immediately:

• Weakness
• Fatigue
• Mouth sores
• Fever

Drug sensitivities can develop over time, with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment.  

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately.  This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

DO NOT USE idoxuridine in:

• Patients with hypersensitivity to the drug

USE WITH CAUTION in:

• Animals that are pregnant or nursing

This drug can cause serious adverse effects in people and animals. Contact your family physician if any exposure to this medication occurs. DO NOT handle this medication if you are pregnant.

Are there any drug interactions I should be aware of?

Certain medications may interact with idoxuridine, so be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Is any monitoring needed with this medication?

• Your veterinarian will let you know when and how they want to reassess your pet to ensure the medication is working and not causing side effects.
• At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.

How do I store idoxuridine?

• Store in the refrigerator and protect from light and freezing.
• Keep the container out of reach of children and pets.
• Store compounded forms of this medication according to the label..

What should I do in case of an emergency?

An overdose of eye medication is unlikely, but side effects or toxic effects could occur if your 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. Be prepared to provide information about the product and your pet's weight and symptoms.