Plegridy (peginterferon beta-1a) is a brand-name injection prescribed to adults for certain forms of multiple sclerosis. As with other drugs, Plegridy can cause side effects, such as injection site reactions.

Plegridy can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who received Plegridy in clinical trials:

Mild side effects can occur with Plegridy use. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to the drug’s prescribing information.

Mild side effects that have been reported with Plegridy include:

  • flu-like symptoms, including:
    • fever or chills
    • headache
    • joint or muscle pain
    • weakness
    • tiredness
  • itchy skin
  • nausea and vomiting
  • mild injection site reactions (see “Side effect specifics” for details)

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking Plegridy and want to tell the FDA about it, visit MedWatch.

Plegridy may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to the Plegridy prescribing information.

If you develop serious side effects while taking Plegridy, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects that have been reported and their symptoms include:

  • blood cell problems, including low white blood cell count, which may include symptoms such as:
    • fever
    • flu-like symptoms
  • cardiomyopathy, which may include symptoms such as:
    • shortness of breath
    • fatigue
  • depression, which may include symptoms such as:
    • losing interest in activities and hobbies you usually enjoy
    • excessive feelings of worthlessness or guilt
  • heart failure, which may include symptoms such as:
    • cough
    • fatigue
    • shortness of breath
  • overactive thyroid gland, which may include symptoms such as:
    • goiter (swelling in your neck due to an enlarged thyroid gland)
    • irritability or mood changes
  • underactive thyroid gland, which may include symptoms such as:
    • fatigue
    • weight gain
  • pulmonary arterial hypertension (elevated blood pressure in the arteries of the lungs), which may include symptoms such as:
    • shortness of breath, particularly after exertion
    • fatigue
  • seizures, which may include symptoms such as:
    • jerky, sudden movements of your arms, legs, head, or neck
    • loss of consciousness
  • suicidal thoughts or behaviors, which may include symptoms such as:
    • withdrawing from family and friends
    • feelings of extreme anxiety, sadness, agitation, or anger
  • thrombotic microangiopathy (damage to small blood vessels), which may include symptoms such as:
    • feeling lightheaded
    • fatigue
  • severe injection site reactions (see “Side effect specifics” for details)
  • liver damage (see “Side effect specifics” for details)
ALLERGIC REACTION

For some people, Plegridy can cause an allergic reaction.

In general, symptoms of allergic reaction can be mild or serious.

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to Plegridy injection, your doctor may recommend taking a different medication instead.

Plegridy injection may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Does Plegridy cause long-term side effects?

In most cases, Plegridy side effects are temporary and last a few days at most. (Refer to earlier sections for details.) But in rare cases, long-term side effects have been reported in people receiving Plegridy. Long-term side effects may refer to side effects that begin after you’ve received Plegridy for a long time. Or, they can refer to side effects that persist even after you stop treatment.

Long-term side effects reported with Plegridy treatment include:

  • severe liver failure (see “Side effect specifics” for details)
  • depression and suicidal thoughts
  • heart failure, which may continue even if you stop receiving Plegridy
  • pulmonary arterial hypertension, which has been reported years after starting treatment
  • thrombotic microangiopathy, which has been reported years after starting treatment

For more information about these side effects, see the “Serious side effects of Plegridy” section. To learn about your risk of long-term side effects from Plegridy, talk with your doctor.

Is Plegridy safe for older adults?

Yes, it appears so. The first clinical trials of Plegridy didn’t include enough older adults (ages 65 years and older) to say for certain that side effects didn’t differ in this age group. But since the drug was approved, studies of Plegridy haven’t noted a difference in side effects in younger versus older adults.

That said, older adults are more likely to have health conditions affecting the heart, kidneys, or liver. And having a preexisting heart, kidney, or liver condition can raise your risk of certain side effects of Plegridy.

Be sure your doctor is aware of your full health history before you begin Plegridy treatment. They’ll help determine whether Plegridy is a safe treatment option for your condition based on your overall health and other factors.

Suicide prevention

If you know someone at immediate risk of self-harm, suicide, or hurting another person:

  • Ask the tough question: “Are you considering suicide?”
  • Listen to the person without judgment.
  • Call 911 or the local emergency number, or text TALK to 741741 to communicate with a trained crisis counselor.
  • Stay with the person until professional help arrives.
  • Try to remove any weapons, medications, or other potentially harmful objects if it’s safe to do so.

If you or someone you know is having thoughts of suicide, a prevention hotline can help. The 988 Suicide and Crisis Lifeline is available 24 hours a day at 988. During a crisis, people who are hard of hearing can use their preferred relay service or dial 711 then 988.

Find more links and local resources.

Learn more about some of the side effects that Plegridy may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Plegridy.

Injection site reactions

Injection site reactions are commonly reported with Plegridy treatment. They refer to side effects that happen at or near the area where you or a healthcare professional injects Plegridy. (You may be able to self-inject your Plegridy doses after a healthcare professional or your doctor shows you how.)

Injection site reactions are usually mild, including any of the following at the area where Plegridy is injected:

Rarely, serious injection site reactions can also happen with Plegridy. Serious injection site reactions reported include:

  • necrosis (death of body tissue)
  • abscesses (a bump or boil on or below the surface of the skin)
  • cellulitis (a bacterial infection in the deeper skin layers)

Injection site reactions can occur at any time you’re receiving Plegridy. They’re more common when the medication is injected under the skin versus into a muscle.

What you can do

To help prevent injection site reactions, rotate the site of Plegridy injections. Do not use the same site for consecutive injections. You can learn how Plegridy is given in .

If you develop a mild injection site reaction, it should go away on its own. Depending on your symptoms, home remedies may help. For example, applying a cold compress may help with pain or warmth.

If you think you’re having a serious injection site reaction, let your doctor know right away. If you develop necrosis at an injection site, your doctor may permanently stop your Plegridy treatment. Or, they may have you continue treatment but avoid injecting the drug near the necrotic site.

Rarely, abscesses and cellulitis caused by Plegridy injections require surgical drainage and treatment with antibiotics in a hospital.

Liver damage

While rare, liver damage has been reported as a side effect with Plegridy treatment. This includes rare reports of liver failure.

Symptoms of liver damage can include:

An early sign of possible liver damage is elevated liver enzymes. This usually doesn’t cause symptoms, but it may be noticed by your doctor if they test to check your liver enzyme levels.

What you can do

During treatment with Plegridy, your doctor may order tests to check your liver enzyme levels. This allows your doctor to monitor your liver health and may help catch developing liver problems before they start causing symptoms. Your doctor may have you temporarily or permanently stop Plegridy treatment if tests show elevations in your liver enzyme levels.

Tell your doctor right away if you notice the above symptoms of liver damage while receiving Plegridy. Your doctor can determine the best way to treat your symptoms. This may include stopping treatment with Plegridy and exploring other treatments for multiple sclerosis.

Below is important information to consider before you begin Plegridy treatment.

Before receiving Plegridy, discuss your health history with your doctor. Plegridy may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

Disclaimer: Medical News Today 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.