Interferon Alfa

By Rania Gollakner, BS, DVM, MPH

What is interferon alfa?

Interferon alfa-2b (brand names: Roferon®-A, Intron®-A) is an immunomodulator and antiviral used to treat viral diseases in cats and dogs, such as feline immunodeficiency virus (FIV) or papillomatosis. This medication is experimental in animals and studies are limited regarding it effectiveness and other factors.

Its use in cats and dogs to treat viral conditions is ‘off label’ or ‘extra-label’. 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 is interferon alfa given?

Interferon alfa is given by mouth in the form of a liquid. It can also be given by injection in the hospital setting. It should be given without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food. Measure the liquid form carefully, and do not vigorously shake the liquid unless otherwise directed. Give this medication directly into the mouth or inside the cheek; do not mix into your pet’s food.

This medication can take up to a few weeks before full effects are obvious, 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 when you remember, but if it is close to the time for the next dose, skip the dose you missed 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 are uncommon when dosed by mouth, but may include vomiting or a decreased appetite. High doses in cats may cause tiredness, allergic reactions, bone marrow problems, and fever. In humans, side effects may include bone marrow suppression, vison problems, lack of appetite, stomach upset, flu-like symptoms, and skin reactions. Studies are limited in animals and it is unclear if the human side effects relate to veterinary patients.

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 interferon alfa in pets that are allergic to it or in pets receiving immediate vaccination. Use the oral form with extreme caution in cats with feline infectious peritonitis (FIP). Interferon alfa should be used with caution in pregnant and lactating pets as studies are limited and safety has not been established in these cases.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with interferon alfa: acyclovir, zidovudine, vidarabine, colchicine, or theophylline.

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 will likely monitor your pet’s complete blood count and blood chemistry panel periodically. Triglyceride levels and a thyroid panel may also be monitored. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet at home for serious side effects.

How do I store interferon alfa?

Store the compounded liquid forms of this medication according to the label. It is usually refrigerated.

What should I do in case of emergency?

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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