Mavenclad (cladribine) is a prescription brand-name medication. It’s approved by the Food and Drug Administration (FDA) to treat certain forms of multiple sclerosis (MS). Specifically, Mavenclad is a safe and effective treatment option for people with:

If Mavenclad is effective for your type of MS, your doctor will likely recommend you take the drug long term.

Here are some fast facts about Mavenclad:

  • Active ingredient: cladribine
  • Drug class: purine antimetabolite
  • Drug form: oral tablet

Like other drugs, Mavenclad tablets can cause side effects. Read on to learn about potential common, mild, and serious side effects. For a general overview of Mavenclad, including details about its uses, see this article.

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:

* To learn more 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 Food and Drug Administration (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 Food and Drug Administration (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 Food and Drug Administration (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 weaken your immune system, 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, your doctor typically will not prescribe Mavenclad. These include hepatitis and tuberculosis.

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.

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

Alcohol use with 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 or nausea. So, drinking alcohol while you are taking Mavenclad may increase your risk of these side effects. (For more information, see “Side effect specifics” above.)

Liver problems are another possible side effect of Mavenclad. Drinking a lot of alcohol over time also increases your risk of liver problems.

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 Food and Drug Administration (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 female* and can 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 if Mavenclad passes into breastmilk or how it might affect a breastfed child. 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 terms “female” and “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 from 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.
  • Mavenclad and 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.