Key takeaways
- Avonex, used to treat certain types of multiple sclerosis, can cause side effects ranging from mild, such as headaches and muscle pain, to serious, including depression and liver damage.
- Long-term side effects from Avonex, like liver damage or depression, can potentially persist even after stopping the medication.
- It’s important to discuss any history of mental health disorders, liver problems, or alcohol use with your doctor before starting Avonex, as these factors can increase the risk of certain side effects.
Avonex is used in adults to treat the following types of multiple sclerosis (MS):
- clinically isolated syndrome (CIS) (which may or may not lead to MS)
- active secondary progressive MS
- relapsing-remitting MS
The active ingredient in Avonex is a
Keep reading to learn about the common, mild, and serious side effects that Avonex can cause.
The most common side effects of Avonex are typically mild. They are:
- weakness
- muscle aches
- fever
- chills
Less common side effects include:
- mild urinary tract infection (UTI) or upper respiratory infection
- headache
- nausea
- joint pain
- dizziness
- hair loss
- injection site reaction, including pain and swelling
- mild allergic reaction
- depression
In most cases, these side effects are temporary and easy to manage. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. Don’t stop using Avonex unless your doctor recommends it.
Avonex may cause mild side effects other than those listed above. See the drug’s prescribing information for details.
Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Avonex, visit MedWatch.
Serious side effects with Avonex are typically rare. These include:
- liver damage
- autoimmune problems such as thyroiditis or hepatitis
- seizure
- low blood counts (platelets, white blood cells, and red blood cells)
- thrombotic microangiopathy (blood clotting disorder)
- congestive heart failure
- pulmonary arterial hypertension (high blood pressure in the lungs’ blood vessels)
- depression and suicide
- severe injection reactions
- severe allergic reaction
If you develop serious side effects while using Avonex, call 911 or your local emergency number.
How to manage depression or suicidal thoughts
Depression was a common side effect reported in studies of Avonex.
Some factors can increase your risk of depression or suicide during Avonex treatment. These include:
- having a history of mental health disorders, depression, or suicide
- having a substance misuse history
- being isolated or lacking social support
If you have risk factors for depression, talk with your doctor before starting Avonex. They may suggest mental health assistance, such as counseling, medication, and group support.
If you’re having suicidal thoughts, call 911 or your local emergency number for an urgent medical evaluation.
Help is out there
If you or someone you know is in crisis and considering suicide or self-harm, please seek support:
- Call or text the 988 Suicide and Crisis Lifeline at 988 or chat at 988lifeline.org. Caring counselors are available to listen and provide free and confidential support 24/7.
- Text HOME to the Crisis Text Line at 741741 to connect with a volunteer crisis counselor for free and confidential support 24/7.
- Not in the United States? Find a helpline in your country with Befrienders Worldwide.
- Call 911 or your local emergency services number if you feel safe to do so.
If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.
If you’re not in the same household, stay on the phone with them until help arrives.
Get answers to some frequently asked questions about Avonex’s side effects.
Does Avonex cause long-term side effects?
It’s possible. Long-term side effects can start at any time you’re using a drug, even if you’ve used it for a long time. They also include side effects that may not go away, even after you stop using the drug.
Examples of long-term side effects reported in Avonex’s studies include:
- bone marrow suppression
- autoimmune problems such as thyroiditis or hepatitis
- pulmonary arterial hypertension (high blood pressure in the lungs’ blood vessels)
- thrombotic microangiopathy (blood clotting disorder)
- congestive heart failure
- injection site tissue death (skin and muscle)
- liver damage, including liver failure
- depression and suicide
If you’re concerned about possible long-term side effects from Avonex, talk with your doctor or pharmacist.
Will I experience certain side effects after stopping Avonex?
No, you shouldn’t experience any side effects from stopping Avonex treatment. Studies show it might take about 4 days after your last dose for your body to remove Avonex completely. After then, you may experience worsening of your MS symptoms or notice no change at all.
If you’re considering stopping Avonex, talk with your doctor or pharmacist first.
Keeping track of side effectsDuring your Avonex treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start a new drug or combination of treatments.
Your side effect notes can include things such as:
- what dose of the drug you were taking when you had the side effect
- how soon you had the side effect after starting that dose
- what your symptoms were
- how your symptoms affected your daily activities
- what other medications you were taking
- any other information you feel is important
Keeping notes and sharing them with your doctor will help them learn more about how Avonex affects you. They can then use this information to adjust your treatment plan if needed.
Below is important information you should consider before using Avonex.
Warnings
Avonex can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Avonex is a good treatment option for you.
Discuss your health history with your doctor before using Avonex. Be sure to tell them if any of the following factors apply to you:
- autoimmune problems
- thyroid problems
- heart problems
- seizure
- liver problems
- low blood counts (platelets, white blood cells, and red blood cells)
- blood clots or bleeding problems
- you drink alcohol
- history of depression, mental health disorders, or suicidal thoughts or behaviors
- you take other medications, over-the-counter drugs, herbs, vitamins, or supplements
- allergy to rubber or latex (Avonex prefilled syringes and auto-injectors contain natural rubber latex.)
- past allergic reaction to Avonex
- pregnancy
- breastfeeding
Alcohol and Avonex
You should not drink excessive amounts of alcohol while using Avonex. Severe liver damage, including liver failure, has been reported with the use of Avonex. So the use of alcohol can increase this risk.
Talk with your doctor or pharmacist if you have questions about drinking alcohol during Avonex treatment. They can tell you how much is safe to drink.
Pregnancy and breastfeeding with Avonex
Before starting Avonex treatment, it’s important to talk with your doctor if you’re pregnant, breastfeeding, or planning either.
Pregnancy
It’s not known whether it’s safe to use Avonex during pregnancy. Research has studied fetal development problems and the use of Avonex or similar drugs during early pregnancy.
The research has shown no connection between these problems and the use of these drugs. But information about the potential risk of low birth weight or pregnancy loss isn’t consistent, so no conclusions can be made.
If you’re pregnant or can become pregnant, talk with your doctor before starting treatment with Avonex.
Breastfeeding
It isn’t known whether Avonex is safe to use while breastfeeding.
Avonex and other drugs similar to it have been found to pass into breast milk at low levels. But information on how this affects the production of milk and a child who is breastfed is limited.
If you’re breastfeeding or planning to do so, talk with your doctor before starting this medication.
If you have questions about side effects that Avonex can cause, talk with your doctor.
Examples of questions include:
- What should I do if I develop an injection site reaction with Avonex?
- How will you monitor me for liver or blood problems from Avonex?
- Is muscle weakness or pain from Avonex something that will go away over time?
- If I get flu-like symptoms from Avonex, will over-the-counter drugs treat them?
- What is my risk of severe side effects from Avonex?
If you’re looking to connect with other people with MS, Healthline’s Bezzy MS offers an online safe space for community, peer and expert guidance, and support.
Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.