Interferon Alfa

What is interferon alfa?

Interferon alfa (brand names: Roferon®-A, Intron®-A) is an immunomodulator and antiviral drug 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 (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 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.
• 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 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?

Interferon alfa may cause the following side effects (rare when dosed by mouth):

• Vomiting
• Decreased appetite

In cats, high doses may cause the following side effects:

• Tiredness
• Allergic reactions
• Bone marrow problems
• Fever

Studies are limited in animals, and it is unclear if human side effects relate to veterinary patients. In humans, side effects may include:

• Bone marrow suppression
• Vison problems
• Lack of appetite
• Stomach upset
• Flu-like symptoms
• Skin reactions

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
• Pets that are receiving immediate vaccination

Use the oral form with EXTREME CAUTION in:

• Cats with feline infectious peritonitis (FIP)

USE WITH CAUTION in:

• Pets that are pregnant and lactating (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
• Colchicine
• Theophylline
• Vidarabine
• Zidovudine

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is any monitoring needed with this medication?

• Your veterinarian will likely monitor your pet’s complete blood count and blood chemistry panel periodically.
• Your veterinarian may monitor triglyceride levels and a thyroid panel.
• Your veterinarian may monitor your pet to be sure that the medication is working.
• 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 interferon alfa?

• Store the compounded liquid forms of this medication according to the label. It is usually refrigerated.
• Keep the container out of reach of children and pets.

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. Be prepared to provide information about the product and your pet’s weight and symptoms.