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Interferons, Alfa

(in-ter-feer-on al-fuh)

Trade/other name(s): Intron A (interferon alfa-2a), Roferon-A (interferon alfa-2b), PEG-Intron (peginterferon alfa-2b), Sylatron (peginterferon alfa-2b), IFN-a, alpha interferon (α interferon)

Why would this drug be used?

Alpha interferons are used to treat certain types of leukemias and lymphomas, skin melanomas, and Kaposi sarcoma. They may also be used to treat other cancers, as well as other conditions (such as hepatitis or genital warts).

How does this drug work?

Interferons are part of a family of proteins called cytokines. Immune system cells in the body normally make small amounts of interferons as a way to communicate with each other. The interferons attach to other immune cells, activating them to help the body fight infections and tumors.

Man-made versions of these substances are sometimes used as a form of immunotherapy – they boost the body's immune system to help it fight diseases, including cancer. Interferons may also slow the growth of tumor cells directly.

While alpha interferons (IFN-α) are more commonly used to help treat certain cancers, other forms of interferon are used to treat other conditions. Manmade forms of interferon beta (IFN-β) help against multiple sclerosis, while forms of interferon gamma (IFN-γ) can be used to treat some other non-cancerous conditions.

Before taking this medicine

Tell your doctor…

  • If you are allergic to anything, including medicines, dyes, additives, or foods.
  • If you have any type of heart disease or any heart rhythm disorder. In some people this drug may affect the heart's function or rhythm.
  • If you have ever had depression, drug or alcohol addiction, or other mental illness. Some people taking this drug have reported feeling depressed or having thoughts of suicide. Some people with addictions go back to drug or alcohol use.
  • If you have ever had lung disease (such as asthma, emphysema, chronic bronchitis) Interferon may cause lung problems or make existing lung problems worse.
  • If you have an autoimmune disease (where the body's immune system attacks the body's own cells, such as rheumatoid arthritis, sarcoidosis, lupus, psoriasis.). This drug may make these conditions worse.
  • If you have any other medical conditions such as kidney disease, liver disease (including hepatitis), thyroid problems, bleeding or clotting problems, congestive heart failure, diabetes, gout, high blood pressure, colitis (inflamed bowel), or high triglycerides (fat in the blood). This drug may make some of these conditions worse. You may need closer monitoring of these conditions while being treated, or the drug dose, regimen, or timing may need to be changed.
  • If you have human immunodeficiency virus (HIV) infection, hepatitis B or hepatitis C.
  • If you have had an organ transplant and must take medicine to keep your body from rejecting the organ.
  • If you have any type of eye problem. This drug may affect your vision or cause existing eye problems to become worse.
  • If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. It is not known if this drug might cause problems if either the male or female is taking it at the time of conception or during pregnancy. Check with your doctor about what kinds of birth control can be used with this medicine. This drug should be used during pregnancy only if the potential benefit is thought to justify the potential risk to the fetus.
  • If you are breast-feeding. While no studies have been done, this drug may pass into breast milk and affect the baby. Talk with your doctor about the possible risks of breast-feeding while taking this drug.
  • If you think you might want to have children in the future. This drug can affect fertility. Talk with your doctor about the possible risk with this drug and the options that may preserve your ability to have children.
  • About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

Telbivudine (Tyzeka, a drug for hepatitis B) may increase the risk of numbness, burning, and tingling in the hands or feet, and trouble walking if given with interferon alfa.

Using this drug with ribavirin may cause a serious type of anemia (hemolytic anemia).

Theophylline (a drug to help breathing) may build up quickly in the body if it is given with interferon alfa, and cause serious side effects.

Any drugs or supplements that interfere with blood clotting can raise the risk of bleeding during treatment with alfa interferons. These include:

  • Vitamin E
  • Non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen (Advil, Motrin), naproxen (Aleve, Naprosyn), and many others
  • Warfarin (Coumadin)
  • Dabigatran (Pradaxa)
  • Heparin injections of any type
  • Ticlopidine (Ticlid)
  • Clopidogrel (Plavix)

Note that many cold, flu, fever, and headache remedies contain aspirin or ibuprofen. Ask your pharmacist if you aren't sure what's in the medicines you take.

Check with your doctor, nurse, or pharmacist about your medicines, herbs, and supplements, and whether alcohol can cause problems with this medicine.

Interactions with foods

No serious interactions with food are known at this time. Check with your doctor, nurse, or pharmacist about whether some foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Interferon alfa is given by an injection. This may be into a vein (intravenous, or IV), under the skin (subcutaneous, or SubQ), or into a muscle (intramuscular, or IM). It may be given in a doctor's office, or you or a family member can be taught how to give the medicine under the skin.

Interferon injections are often given either daily or several times a week, but the dose and the number of doses depend on your body size, general health, and the type of cancer being treated. Different brands of interferon may have different strengths, so make sure you are using the same brand over time.

Make sure you know your correct dose and exactly how this drug is to be given before you take it. If you are not sure, call your doctor or nurse for a review of the instructions.

Keep this medicine in its original container and store it in the refrigerator. Do not freeze the powder or liquid. Store the syringes, needles, and supplies in a safe place, out of the reach of children and pets.

Use a special sharps container to dispose of the used syringes and needles. You should be able bring the filled sharps container back to your doctor's office once it's full. Ask your nurse or doctor about this.


Most people taking this drug experience flu-like symptoms, which can include feeling tired all the time, as well as fevers, headache, and muscle and joint pains. This may interfere with your ability to perform certain tasks. Drinking plenty of fluids and taking medicines for the fever and pain may help you.

This drug may cause drowsiness and may affect activities such as driving. Wait until you find out how it affects you before driving or operating other dangerous machinery. Alcohol, sedatives, "nerve pills," or sleeping pills may worsen this effect.

Some people notice feeling depressed or even having thoughts of suicide while on this drug. A few people become aggressive or threatening towards others. Tell your doctor or nurse right away if you note serious changes in your mood or emotions.

This drug can cause allergic reactions in some people when the drug is given. Mild reactions usually consist of fever and chills. More serious reactions happen rarely, but can be dangerous. Symptoms can include feeling lightheaded or dizzy (due to low blood pressure), fever or chills, hives, skin rash or blisters, nausea, itching, headache, coughing, shortness of breath, or swelling of the face, tongue, or throat. Tell your doctor or nurse right away if you notice any of these symptoms during or after being given the drug. Your doctor or nurse will likely give you medicine to try to prevent a reaction.

Your doctor will likely test your blood throughout your treatment, looking for possible effects of the drug on blood counts (described below) or on other body organs. Based on the test results, you may be given medicines to help treat any effects. Your doctor may also need to reduce or delay your next dose of this drug, or even stop it altogether. Keep all your appointments for lab work and doctor visits.

This drug can lower your white blood cell count, especially in the weeks after the drug is given. This can increase your chance of getting an infection. Be sure to let your doctor or nurse know right away if you have any signs of infection, such as fever (100.5° or higher), chills, diarrhea, pain or burning when passing urine, new onset of cough, or bringing up sputum.

This drug may lower your platelet count in the weeks after it is given, which can increase your risk of bleeding. Speak with your doctor before taking any drugs or supplements that might affect your body's ability to stop bleeding, such as aspirin or aspirin-containing medicines, warfarin (Coumadin), or vitamin E. Tell your doctor right away if you have unusual bruising, or bleeding such as nosebleeds, bleeding gums when you brush your teeth, or black, tarry stools.

This drug may lower your red blood cell count. If this occurs, it is usually a few months after starting treatment. A low red blood cell count (known as anemia) can cause shortness of breath, or make you to feel weak or tired all the time. Your doctor may give you medicines to help prevent or treat this condition, or you may need to get blood transfusions.

This drug may affect the eyes. Your doctor will likely examine your eyes before you start treatment. Let the doctor know right away if you notice changes in your vision.

Some people develop high blood sugar or even diabetes while on interferon, with symptoms such as increased thirst, losing weight, feeling tired, and bigger appetite.

Do not get any immunizations (vaccines), either during or after treatment with this drug, without your doctor's OK. Alfa interferons may affect your immune system. This could make vaccinations ineffective, or even lead to serious infections if you get a live virus vaccine during or soon after treatment. Try to avoid contact with people who have recently received a live virus vaccine, such as the oral polio vaccine or smallpox vaccine.

Call your doctor if you have cough, chest pain, or trouble breathing, or if you have severe pain in the belly or lower back.

Men and women should avoid conceiving a baby while getting this drug and for 6 months afterward. It should not be used during pregnancy, and men whose sex partners are pregnant should not get this drug. This drug can cause birth defects and other harm to the fetus. Talk with your doctor about the kinds of birth control that you and your partner can use during and after treatment. (Couples are usually asked to use 2 kinds of birth control for this entire time.)

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.


  • Flu-like syndrome (may include fever, chills, tiredness, headache, muscle and joint pain)
  • Feeling tired or drowsy*
  • Headache
  • Nausea
  • Loss of appetite
  • Hair thinning or loss (may include face and body hair)

Less common

  • Low white blood cell count with increased risk of infection*
  • Low platelet count with increased risk of bleeding*
  • Depression, thoughts of suicide, or aggression*
  • Dizziness
  • Confusion
  • Mild diarrhea
  • Abdominal pain
  • Trouble sleeping
  • Trouble concentrating
  • Irritation at the place of injection
  • Hair thinning or hair loss
  • Abnormal blood tests which suggest that the drug is affecting the thyroid gland
  • Abnormal blood tests which suggest that the drug is affecting the liver or kidneys (Your doctor will discuss the importance of this finding, if any.)


  • Low red blood cell count (anemia) with symptoms like tiredness and shortness of breath*
  • Decrease in or loss of vision*
  • Allergic reaction*
  • Changes in taste or smell
  • Vomiting
  • Cough*
  • Shortness of breath*
  • Chest pain
  • Faster heart rate or change in heart rhythm
  • Low blood pressure (which may cause dizziness or fainting) during or up to 2 days after treatment
  • Diabetes*
  • Thyroid problems
  • Rash or dry skin
  • Sweating
  • Dry mouth or throat
  • Tingling sensations or numbness in hands or feet
  • Stroke or stroke-like symptoms with weakness, numbness, and trouble with coordination
  • Heart attack
  • Heart muscle problems (cardiomyopathy)
  • Problems with the liver that can include nausea, yellow skin or eyes, bleeding, or coma
  • Congestive heart failure (can cause shortness of breath or swelling in hands or feet)
  • Death due to lung failure, liver failure, autoimmune disease, suicide, or other cause

*See "Precautions" section for more detailed information.

There are some other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved in 1986.

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.

Last Medical Review: 07/16/2012
Last Revised: 07/16/2012