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Answers to the Most Commonly Asked Questions About Interferons

In this article, we answer some of the most frequently asked questions about interferons, detailing how they work, when they can be used, and possible side effects.

Interferons belong to a group of proteins called cytokines which act as neurotransmitters between different cells. These endogenic signaling proteins are produced by host cells and serve the immune system by triggering defensive reactions in response to the presence of pathogens in the body. They can be genetically engineered to treat diseases of the immune system (autoimmune diseases, e.g. multiple sclerosis), cancers and infectious diseases.

In this article we answer the 19 most frequently asked questions about interferons. Read on to find out more.

The content on this page is provided for informational purposes only. If you have any questions or concerns about your treatment, you should talk to your doctor, pharmacist, or healthcare professional. This is particularly important if you are taking multiple medications or have any existing medical conditions.

What are interferons?

Interferons are endogenic proteins that form an important part of the immune system. They are released by host cells in response to the presence of pathogens, for example a viral infection or a tumor. They “interfere” with viral production and protect cells from infection, regulating the immune system’s activity.

Through biotechnological methods, they are produced as medicines and belong to the active ingredient class of immunomodulating (immune-strengthening or debilitating) agents.

How many different types of interferons are there?

There are various types of interferons that are each made up of different types of cells. Interferon-alpha (INF-α), interferon-beta (INF-β) and interferon-gamma (INF-γ) are genetically engineered and produced for use as a drug (see Question 9: When are specific interferons used? and Question 10: In what forms are interferons available?) There are also interferons called peginterferons (see Question 3: What is a peginterferon?)

What is a peginterferon?

A peginterferon, short for pegylated interferon, is an interferon that is chemically paired with polyethylene glycol (PEG). Due to their longer half-life, peginterferons only need to be administered once a week (instead of about three times a week) for them to have the same effect as standard interferon therapy. The pegylation of the active substance causes the interferon to be released more slowly and excreted at a slower rate through the kidneys, therefore it remains in the blood for a longer period. By comparison, the half life of non-pegylated active ingredients is a few hours, whereas peginterferons can have a half-life of 40 to 80 hours.

What is interferon therapy?

Genetically engineered interferons are used to treat autoimmune and infectious diseases as well as certain cancers, often for several months or even years. Here are some examples:

Autoimmune diseases

  • Multiple Sclerosis
  • Chronic granulomatous disease


  • Chronic myeloid leukemia
  • Hair cell leukemia
  • Cutaneous T-cell lymphoma
  • Kaposi sarcoma in AIDS patients
  • Malignant melanoma
  • Renal cell carcinoma

Infectious diseases

  • Chronic hepatitis B and C
  • Condylomata acuminata (genital warts)

Are interferons a type of chemotherapy?

Interferon therapy is immunotherapy that can be used to support other therapies such as chemotherapy in the treatment of certain cancers. In cancer therapy, interferons can slow the growth of tumor cells and stop the growth of blood vessels that supply the tumor with blood. They can make it easier for the immune system to detect and attack the tumor and increase the impact of natural killer cells (NK cells) and other immune cells.

How do interferons work?

Interferons activate the defense mechanisms of both virus-infected cells and the surrounding healthy cells. In doing so interferons can have the following effects:

  • Antiviral effect: The activated cells produce proteins that inhibit virus replication in the infected cells. Interferon alpha also activates natural killer cells (NK cells) which are used to fight viruses and tumors.
  • Antiproliferative effect: Interferons cause the disintegration of the transport substances (RNA) necessary for protein formation in the activated viruses and cells.
  • Immunomodulatory effect: Special white blood cells (T-lymphocytes) circling in the blood are activated, making virus-infected cells more vulnerable to them.

How do interferons work with MS?

In the treatment of multiple sclerosis, the interferon supplied is intended to reduce the number of active inflammatory cells. Interferon therapy should also prevent these cells from penetrating the central nervous system. These defense processes weaken the disease activity, as can be seen on magnetic resonance imaging (MRI).

Studies have confirmed that interferon-beta therapy helps to reduce the number of MS episodes and that these episodes take a less severe course. It has also been shown that the onset of disability could be delayed by two years as a result of interferon treatment. A longer delay has not yet been satisfactorily demonstrated.

Are interferons immunosuppressant?

Interferons belong to the group of immunomodulating drugs. While immunosuppressive drugs suppress the functions of the immune system, immunomodulating drugs alter the immune system through various principles of action. Immunomodulating drugs can subdue the immune system (immunosuppression) or stimulate it.

When are specific interferons used?

Interferon beta

  • Interferon beta-1a as a therapy for relapsing-remitting multiple sclerosis (RRMS) or interferon beta-1b for MS that progressively worsens between relapses.
  • For serious viral diseases

Interferon alpha

  • For renal cancer and some forms of blood and skin cancer:
    o Chronic myeloid leukemia
    o Hair cell leukemia
    o T-cell lymphoma of the skin
    o Malignant melanoma
    o Kaposi sarcoma

  • For chronic hepatitis B and C (interferon -alpha-2a or interferon -alpha-2b)

Interferon gamma

  • For septic granulomatosis (a very rare hereditary disease of the immune system)
  • For osteopetrosis (so-called marble bone disease, a mostly genetic disease caused by the absence or hypofunction of bone-degrading cells)
  • For various cancers, such as ovarian cancer

In what forms are interferons available?

Interferons are only available as injections, for example in the form of syringes pre-filled with injection solution.

The following active substances (with trade names) belong to the interferon actives substances group:

Things to consider before taking interferons

Interferons should not be used in the following circumstances:

  • In the case of allergies to the active substance or other ingredients in the medicine
  • In the case of severe depression and risk of suicide

The attending physician should consider the benefits and risks of interferon therapy regarding the following conditions:

  • Diseases of the bone marrow
  • Renal and hepatic impairment
  • Cardiovascular disease
  • Epilepsy that is not treatable
  • Thyroid hypofunction
  • Severe deficiency of white blood cells (leucopenia) or platelets (thrombopenia)
  • During pregnancy or breastfeeding, depending on the active ingredient. See Question 19: Can I take interferons whilst pregnant or breastfeeding?

A full list of precautions can be found in the information leaflet that comes with the medication.

What to look out for during interferon therapy

During interferon treatment, blood clots may occur in the small blood vessels and may have an effect on the kidneys for several weeks to several years after the start of the treatment. The attending physician must monitor blood pressure, blood count (the number of platelets in the blood), and kidney function throughout interferon therapy.

In about 25% of people treated with interferon, antibodies are produced that can weaken the effect of the interferon. The attending physician should reconsider interferon therapy if it is shown to have little effect and if neutralizing antibodies are detected in the bloodstream.

How is interferon stored?

Interferon injection preparations are usually stored in the refrigerator at a temperature of 2-8 degrees Celsius.

How are interferons administered?

Interferons are typically injected under the skin or into the muscle. In some cases, interferon therapy may be administered intravenously. Depending on how long the effects last, they must be administered every 2-3 days or on a weekly basis.

The first injections are carried out under the supervision of trained medical professionals. After the training, pre-filled syringes can be used at home or administered by relatives or nurses.

What side effects can interferon have?

Possible side effects of interferon treatment include:

  • Flu-like symptoms: fever, chills, fatigue, muscle and joint pain
  • Reactions at the injection site: redness of the skin, pain, swelling and inflammation
  • Diseases of the blood: leucopenia, thrombocytopenia, anemia
  • Liver dysfunction
  • Sleeping disorders, headaches
  • Gastrointestinal symptoms: nausea, abdominal pain, diarrhea, weight loss
  • Psychopathological changes: depression, irritability
  • Menstrual irregularities of prolonged and increased menstrual bleeding in women

It is also possible to experience long-term side effects of interferon treatment. In rare cases, disorders of the small blood vessels and kidneys can still occur years after the onset of interferon therapy. These are detectable at the first occurrence of hypertension, fever and confusion, as well as discomfort in the limbs and swollen ankles (edema).

This is not an extensive list of possible side effects of interferons. For more information about side effects, please read the information leaflet that comes with the medication or speak to your doctor or pharmacist.

How can the side effects of interferon therapy be treated?

Flu-like symptoms often occur at the beginning of treatment or are dependent on the dose and can be alleviated or eliminated with paracetamol. Haematopoiesis could also cause flu-like symptoms such as fatigue and fever, which persist for a long time. In such cases, the blood count must be checked by the attending physician.

Recommended prevention measures against injection site reactions include:

  • Removing the pre-filled syringe from the refrigerator about 30 minutes before administration and allowing it to warm to room temperature
  • Washing your hands thoroughly before injecting
  • Thoroughly cleansing the skin at the injection site with water and soap, which is less irritating for the skin than alcohol swabs. If alcohol swabs are used (e.g. when travelling or during hospital stays), allow the skin to dry for at least 60 seconds after use
  • Changing the injection site regularly
  • Regularly cooling any swelling at the puncture site with a cold compress. Apply heat to any swelling that lasts longer than 1 day
  • Treating skin rashes with ointments that contain anti-allergic agents (antihistamines) such as diphenhydramine (Dermodrin ointment), hydrocortisone cream or creams containing witch-hazel as an active ingredient.

Do interferons interfere with other drugs?

It is possible that interferons can reduce the activity of liver enzymes that break down other active ingredients. This can cause a delay, for example, in the breakdown of antidepressants or antiepileptic drugs, which are almost completely metabolized in the liver. If necessary, the dosage of these drugs must be adjusted.

Caution should also be exercised when using additional active substances affecting the liver and the hematopoietic system, as this can lead to an increased risk of side effects.

Interferon treatment can increase the risk of organ rejection in transplant patients taking immunosuppressants.

Interferons can also enhance the effects and side effects of theophylline (a drug used for asthma) by causing, for example, headaches, nausea, vomiting and a rapid heartbeat.

Other known interferences are listed below; however, this is not a complete list.

Interferon beta

No interaction studies have been carried out for interferon-beta. Due to a lack of clinical experience, concomitant administration of other immunomodulators other than glucocorticoids and ACTH is not recommended during interferon beta treatment. Interferon may react with the antiretroviral (HIV/AIDS treatment), zidovudine.

Interferon alpha

Interferon -alpha and peginterferon -alpha should not be taken together with telbivudine (used for hepatitis B), as it can cause damage to the peripheral nerves.

Interferon gamma

Interactions with interferon gamma have been ascribed to liver, kidney, neuro- and cardiotoxic agents, myelosuppressive agents, serum proteins, immunological preparations such as vaccines and CYP substrates.

Can I drive whilst undergoing interferon treatment?

In the case of side effects such as fatigue and exhaustion, it is not advisable to drive, operate machines, or carry out hazardous work. Seek advice from your doctor about this.

Can I take interferons whilst pregnant or breastfeeding?

The European Medicines Agency (EMA) has approved the continuation of a necessary ongoing interferon beta treatment during pregnancy. According to research, treatment with interferon beta does not increase the risk of experiencing a miscarriage. It is recommended that you discuss the benefits and risks or interferon treatment during pregnancy with an attending physician.

Interferon treatment can be continued whilst breastfeeding. Due to the small amounts of interferon that are transferred into breast milk and poor absorption of the substance, it is not expected to have any harmful effects on the newborn child.

The content on this page is provided for informational purposes only. If you have any questions or concerns about your treatment, you should talk to your doctor, pharmacist, or healthcare professional. This is particularly important if you are taking multiple medications or have any existing medical conditions.