Mavenclad (cladribine) is a brand-name oral tablet that’s prescribed for relapsing-remitting multiple sclerosis (MS) and active secondary progressive MS. As with other drugs, Mavenclad can cause side effects, such as upper respiratory tract infection and headache.

Mavenclad 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. But if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are a few of the more common side effects of Mavenclad reported in clinical trials:

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

Mild side effects that have been reported with Mavenclad include:

These side effects may be temporary, lasting a few days to weeks. But 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 side effects of the medication. If you develop a side effect while taking Mavenclad and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.

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

If you develop serious side effects while taking Mavenclad, 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:

* For more information about this side effect, see “Side effect specifics” below.
† Mavenclad has a boxed warning for this side effect. This is the most serious warning from the FDA.
‡ To learn more, see “Pregnancy and breastfeeding while taking Mavenclad” in the “Precautions for Mavenclad” section below.

How long Mavenclad side effects last

How long a side effect of Mavenclad lasts may depend on the type of side effect you have. For example, if you have headaches or nausea from Mavenclad, your side effects may be short term. However, other side effects, such as hair loss, heart failure, or cancer, may be long-term side effects.

If you are concerned about how long side effects from Mavenclad may last, talk with your doctor.

Learn more about some of the side effects Mavenclad may cause.

Hair loss

Hair loss is a side effect that may occur with Mavenclad. However, this was not a common side effect in clinical trials.

What you can do

If you experience hair loss during your treatment with Mavenclad, talk with your doctor. They may be able to recommend ways to reduce this side effect. For example, your doctor may recommend certain shampoos or other medications to decrease your risk of hair loss.

Nausea

Nausea may happen during Mavenclad treatment. In clinical trials, nausea was a common side effect.

What you can do

If you are experiencing nausea from taking Mavenclad, talk with your doctor. They may recommend taking your dose with food. Or they may recommend medications to prevent nausea during your Mavenclad treatment.

Headache

Some people may experience headaches during Mavenclad treatment. Headaches were one of the most common side effects reported by people taking this drug in clinical trials.

What you can do

If you experience headaches that are severe or bothersome during Mavenclad treatment, talk with your doctor or pharmacist. They may be able to recommend over-the-counter pain medications, such as Tylenol (acetaminophen), to relieve your headaches.

Cancer

Mavenclad has a boxed warning for the risk of developing cancer. A boxed warning is the most serious warning recommended by the FDA. It alerts patients and doctors about serious side effects.

Although rare, Mavenclad may increase your risk of developing cancer. This may include pancreatic cancer, skin cancer, or ovarian cancer. Some general symptoms of cancer may include:

What you can do

Be sure to tell your doctor if you have a history of cancer or if you’re currently being treated for cancer. If you’re currently having cancer treatment, your doctor will not prescribe Mavenclad.

Additionally, after you take two treatment courses of Mavenclad, your doctor will likely recommend not taking this medication again for 2 years. This is because there is an increased risk of cancer if you take Mavenclad again within a 2-year period.

Your doctor will monitor you throughout your Mavenclad treatment for cancer symptoms. They may recommend more frequent monitoring if you’ve had cancer in the past.

Allergic reaction

As with most drugs, Mavenclad can cause an allergic reaction in some people. This was a common side effect.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • swelling under your skin, typically in your lips, eyelids, feet, or hands
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking Mavenclad. But if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Talk with your doctor about any other medical conditions you have before you start taking Mavenclad. In some cases, certain medical conditions may make it unsafe for you to take Mavenclad.

Boxed warnings

This drug has boxed warnings. These are serious warnings from the FDA. Mavenclad’s boxed warnings are about the following:

  • Cancer: Mavenclad increases your risk of cancer, especially if you’ve had it in the past. Your doctor will not prescribe Mavenclad if you currently have cancer. For details, see the “Side effect specifics” section above.
  • Risk of harm to a fetus: Mavenclad is not safe to take while you’re pregnant. To learn more, see “Pregnancy and breastfeeding while taking Mavenclad” below.

Other precautions

Be sure to talk with your doctor about your health history before you take Mavenclad. This drug may not be the right treatment if you have certain medical conditions or other factors that affect your health. The conditions and factors to consider include:

Infections: If you have any infections* that are active (currently causing symptoms) or inactive (not causing symptoms), be sure to tell your doctor before you start taking Mavenclad. This medication may reduce your immune system activity, which may make it harder for you to fight infections.

Your doctor will likely recommend treating your infection before you start taking Mavenclad. If you have certain types of long-term infections that are currently active (causing symptoms), your doctor typically will not prescribe Mavenclad. These include active hepatitis and active tuberculosis.

Heart problems: If you have heart problems, be sure to discuss this with your doctor before starting Mavenclad. Heart problems, including heart failure, are possible side effects of Mavenclad. Your doctor can determine whether Mavenclad treatment is safe for you.

If you develop symptoms of heart failure while you’re taking Mavenclad, contact your doctor or get emergency medical help. Possible symptoms include shortness of breath, a fast or irregular heart rate, and swelling.

History of chickenpox or shingles: Be sure your doctor knows whether you’ve had chickenpox or shingles in the past. Mavenclad increases your risk of infections, including shingles. It’s recommended to have the varicella (chickenpox) vaccine before starting Mavenclad. Your doctor can help you determine whether you need this vaccine.

HIV: Mavenclad is not prescribed for use in people with HIV. The drug can make HIV worse. If you have HIV, your doctor will recommend a medication other than Mavenclad for your condition.

Allergic reaction: If you’ve had an allergic reaction* to Mavenclad or any of its ingredients, your doctor will likely not prescribe Mavenclad. Ask your doctor about other medications that may be better options for you.

Graft-versus-host disease after blood transfusions: If you’re prescribed Mavenclad, be sure to tell your doctor before getting any blood transfusions. Mavenclad may increase your risk of developing graft-versus-host disease. If you need any blood transfusions during your Mavenclad treatment, tell your doctor you’re taking this medication. They can recommend a special type of transfusion to reduce your risk of graft-versus-host disease.

Liver conditions: Mavenclad may cause liver problems. If you already have liver problems, taking Mavenclad may make your condition worse. Your doctor may recommend blood tests throughout your treatment with Mavenclad to monitor your liver function. Depending on the test results, your doctor will determine whether you should continue Mavenclad treatment.

Recent live vaccination: If you receive a live vaccine shortly before starting Mavenclad or while you’re taking Mavenclad, there’s a risk of developing an infection from the vaccine. (Live vaccines contain a small amount of weakened live virus or bacteria. Unlike inactive vaccines, which don’t contain any live virus or bacteria.) Examples of live vaccines include the vaccines for measles, mumps, and rubella (MMR) and the vaccine for shingles. Your doctor can recommend when it’s safe to start Mavenclad after receiving a live vaccine.

* For more information, see “Side effect specifics” above.

Alcohol and Mavenclad

Mavenclad is not known to interact with alcohol. But it is possible that alcohol may make side effects from Mavenclad worse. For example, both alcohol and Mavenclad can cause headaches, nausea, and liver problems. So, drinking alcohol while you’re taking Mavenclad may increase your risk of these side effects. (For more information, see “Side effect specifics” above.)

If you’d like to drink alcohol during your treatment with Mavenclad, talk with your doctor about how much, if any, is safe for you.

Pregnancy and breastfeeding while taking Mavenclad

Mavenclad has a boxed warning about risk of harm to a fetus. A boxed warning is the most serious warning recommended by the FDA. It alerts patients and doctors about serious side effects.

Mavenclad is not safe for you to take while you are pregnant or breastfeeding.

There aren’t any studies on the use of Mavenclad during human pregnancy. However, the drug has caused problems with fetal development (commonly known as “birth defects”) and fetal death in animal studies. But animal studies do not always indicate what may happen in humans.

If you’re able to become pregnant, your doctor will recommend that you:

  • Use birth control to avoid pregnancy during Mavenclad treatment and for at least 6 months after your last dose.
  • Have a pregnancy test before each Mavenclad treatment cycle to be sure you aren’t pregnant.
  • Do not breastfeed while taking Mavenclad or for at least 10 days after your last dose. It’s not known whether Mavenclad passes into breast milk or how it might affect a child who’s breastfed. But due to possible risks of exposing a child to the drug, breastfeeding during or within 10 days after Mavenclad treatment is not recommended.

If you’re male* and your partner can become pregnant, you should use birth control during Mavenclad treatment. And you should continue using it for at least 6 months after your last dose to prevent pregnancy.

* Sex and gender exist on spectrums. Use of the term “male” in this article refers to sex assigned at birth.

Most side effects that you may experience from Mavenclad are mild. However, serious side effects are possible as well. If you’d like to learn more about Mavenclad, talk with your doctor or pharmacist. They can help answer any questions you have about side effects of taking the drug.

Besides talking with your doctor, you can do some research on your own. These articles might help:

  • More information about Mavenclad:For details about other aspects of Mavenclad, refer to this article.
  • Dosage: For information about the dosage of Mavenclad, view this article.
  • Mavenclad for multiple sclerosis (MS): If you’d like to learn more about Mavenclad’s use in treating MS, see this article.
  • Drug comparisons: Learn how Mavenclad compares with Ocrevus and Mayzent.
  • A look at MS: For details about MS, see our MS hub and list of MS articles.

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.