If you have multiple myeloma, your doctor might suggest Blenrep as a treatment option for you. Blenrep is a prescription medication that’s used in adults to treat this type of cancer in certain situations. Learning more about the possible side effects of Blenrep can help you and your doctor better personalize your treatment plan.

The active ingredient in Blenrep is belantamab mafodotin-blmf. An active ingredient is what makes a drug work. Blenrep is a biologic drug, which means it’s made from living cells.

This drug is given by a healthcare professional as an intravenous (IV) infusion (an injection given slowly into a vein) at a doctor’s office or clinic.

For more information about Blenrep, including details about its use, see this in-depth article.

Blenrep can cause mild to serious side effects. Continue reading to learn more.

Mild or serious side effects may occur during treatment with Blenrep.

Blenrep has been reported to have some side effects.

The side effects explained section is where you can learn more about this side effect.

Blenrep has a number of possible side effects.

Mild side effects can be caused by blenrep treatment.

Mild side effects have been reported with Blenrep.

The side effects explained section is where you can learn more about this side effect.

These side effects should be short term. Some may be easy to manage. If you have any symptoms that bother you, talk to your doctor or pharmacist. They can discuss your concerns with you.

Blenrep may cause mild side effects other than the ones listed above. See the Blenrep prescribing information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Blenrep, visit MedWatch.

“Some people may have more serious side effects than others. There is a way to measure how severe a side effect is. It can be determined by factors such as a person’s health and their medication.”

Serious side effects include:

* Blenrep 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 the “Side effects explained” section below.
† To learn more about this side effect, see the “Side effects explained” section below.
‡ An allergic reaction is possible after using Blenrep. But it’s not clear whether this side effect occurred in studies.

If you develop serious side effects while taking Blenrep, call your doctor. If the side effects seem life threatening or you think you have a medical emergency, immediately call the emergency number.

Some of the side effects Blenrep may cause are discussed.

Risk of serious eye problems

Blenrep has a boxed warning for risk of serious eye problems (also known as ocular side effects). A boxed warning is the most serious warning from the Food and Drug Administration (FDA). It alerts doctors and patients about drug effects that may be dangerous.

Blenrep may cause changes to the cornea, which is the outer layer in the front part of the eye. These changes may result in corneal ulcers (sores), dryness, blurred vision, and, in serious cases, loss of vision.

What might help

Before you begin treatment with Blenrep, your doctor will ask you to visit an eye doctor to check your eyes. This is part of a safety program called the Blenrep Risk Evaluation and Mitigation Strategy (REMS). For more information about this program, see the section just below.

If you are receiving Blenrep, you will have your eyes checked before each dose.

If you have any eye related side effects, you should contact your doctor. They will ask an eye specialist to examine your eyes. If the results are not good, your doctor may lower your dose. or stop treatment.

Blenrep REMS Program

The Blenrep REMS Program is a safety program designed to manage eye-related risks associated with Blenrep. Your doctor must be specially trained, and the clinic where you receive Blenrep must be certified to give the drug. You will also have to enroll in the Blenrep REMS program to receive this drug.

If you have questions, talk to your doctor.


Blenrep may cause nausea. In studies of the drug, this was a commonly reported side effect.

“Most people don’t experience nausea with time. In some cases, nausea may be more serious.”

What might help

A healthcare professional will give you Blenrep as an intravenous (IV) infusion (an injection given slowly into a vein) at a doctor’s office or clinic. They’ll monitor you during and after you receive your dose.

The healthcare professional may stop or slow your treatment if you experience nausea during your injection. The nausea is not serious for most people.

Try to eat smaller, more frequent meals and avoid greasy foods. The side effect may be alleviated by drinking ginger tea or the peppermint team.

Your doctor can suggest other ways to manage this side effect.

If you have nausea or vomiting during Blenrep treatment, talk to your doctor. They can discuss your treatment plan with you.


In studies of Blenrep, fatigue (low energy) was one of the more commonly reported side effects. Fatigue eases over time for most people during Blenrep treatment. But in some cases, it can last longer and be more serious.

Multiple myeloma, the condition you are using this drug to treat, or other medications may cause fatigue.

What might help

Your doctor will check your blood cell count while you are receiving Blenrep. Blood cells can be low.

To help alleviate the side effect, try getting adequate rest, eating a healthy diet, and not overexerting yourself. Your doctor can offer other suggestions to manage fatigue.

If you have a serious case of fatigue, talk to your doctor. They may suggest other treatment options that are more suited for you.


Blenrep can often cause fever, which is usually considered a mild side effect. But in some cases, fever may be a sign of an infection, which can be serious. Blenrep can cause severe infections such as pneumonia or sepsis (serious blood infection).

What might help

If you have a high temperature while receiving Blenrep treatment, contact your doctor. They may order blood tests to check for an illness. If you have an illness, they will likely stop you from receiving Blenrep and treat it.

If you have a mild fever, your doctor may suggest taking an over-the-counter (OTC) fever reducer to ease this side effect. An example is Tylenol (acetaminophen). Before taking any OTC products, always talk with your doctor. They can recommend a fever reducer that is safe for you.

Low platelet levels

Treatment with Blenrep may cause low platelet counts. (Platelets are a type of blood cell that helps your blood to clot.) This was a common side effect in studies of the drug.

This condition may increase your risk of severe bleeding problems, including hemorrhage (serious internal bleeding).

There are symptoms of low platelet levels.

What might help

Your doctor will keep an eye on your blood cell levels. Your doctor may be able to tell if your platelet counts are low.

  • lower your dose.
  • Delaying or skipping your treatment will let your platelet levels increase.
  • In rare cases of a serious reaction, stop treatment permanently.

If you have symptoms such as It was bruise easily. or bleeding, contact your doctor. They can order blood tests and, based on your platelet levels, discuss options for your treatment plan.

Allergic reaction

Like most drugs, Blenrep can cause an allergic reaction in some people. But it’s not clear whether this side effect occurred in studies.

Mild to serious symptoms can be present.

  • There is a skin rash.
  • It is itchy.
  • flushing (temporary warmth, redness, or deepening of skin color)
  • “It’s usually under your skin, but it can be anywhere.”
  • It can be hard to breathe if you have swelling of your mouth, tongue, or throat.

What might help

If you have a mild rash, call your doctor. They may suggest a treatment to help you. Examples include:

  • an over-the-counter antihistamine you take by mouth, such as Benadryl (diphenhydramine)
  • You apply a product to your skin.

If your doctor confirms you have an allergic reaction to Blenrep, they will decide if you should continue using it.

If you have a severe allergic reaction, you should call the emergency number. These symptoms could be life threatening and need immediate medical care.

If your doctor confirms you have had a serious allergic reaction to Blenrep, you may have to switch to a different treatment.

Keeping track of side effects

Take notes on any side effects you are having during your Blenrep treatment. You can share this information with your doctor. This is helpful when you are starting to use a combination of treatments.

Side effect notes can include things.

  • When you had the side effect, what dose of the drug was taking?
  • How soon did you experience the side effect?
  • What are your symptoms?
  • How did it affect your daily activities?
  • What other drugs were you taking?
  • Other information is important to you.

Sharing notes with your doctor will help them learn more about how Blenrep affects you. If needed, they can use this information to adjust your treatment plan.

There are answers to some frequently asked questions about Blenrep.

Can treatment with Blenrep cause liver damage?

It’s possible. Blenrep can increase liver enzyme levels. This can cause liver damage if it’s severe. But it’s currently not known whether you have higher risk of liver damage from Blenrep if you have liver disease.

If you have a history of liver disease, tell your doctor.

  • jaundice (yellowing of the skin or whites of the eyes)
  • fatigue is low energy
  • There is belly pain.

Your doctor will order blood tests to check your liver function while you’re receiving Blenrep. If your liver enzymes are high, they may pause Blenrep treatment and do more testing. In serious cases, they may stop treatment permanently.

Talk to your doctor about the damage to your body.

Does Blenrep cause shortness of breath?

It’s possible. Although shortness of breath was not reported in studies of Blenrep, the drug may cause infusion-related reactions. These are side effects that can happen during treatment or within a short time after. Shortness of breath is a possible serious reaction of infusions. Other serious infusion-related side effects include headache, chest pain, changes in blood pressure, and seizures.

The healthcare professional will be watching you while you receive the drug. They will likely stop the infused and treat your reaction if you develop side effects. They may resume the infusion at a slower rate. If you have another reaction, they may stop Blenrep treatment permanently.

Your doctor will discuss the possible side effects of Blenrep with you. This includes what you can expect during an injection.

Can I drive after receiving treatment with Blenrep?

It depends on your reaction to treatment. Blenrep can cause eye problems, including blurred vision. Before you start using Blenrep and before you receive each dose, your doctor will have an eye doctor check your vision. They’ll also send you to an eye doctor if there are any changes or problems with your vision.

Caution is needed when driving after treatment with Blenrep due to the possibility of eye-related side effects. It is helpful to have someone to drive you home after the first few infusions.

If you have any questions about this side effect or if it is safe to drive after treatment, talk to your doctor.

Blenrep has several warnings. Discussing the warnings with your doctor can help you decide if this drug is a good option for you.

Boxed warning: Risk of serious eye problems

Blenrep has a boxed warning for the risk of serious eye problems. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

Blenrep may cause changes to the cornea, which is the outer layer in the front part of the eye. If you already have eye problems, let your doctor know. Treatment with Blenrep may increase your risk of eye problems.

Blenrep is only available through a program called the Blenrep Risk Evaluation and Mitigation Strategy.

To learn more, see the “Side effects explained” section above.

Other warnings

If you have a medical condition that affects your health, blenrep may not be right for you. Before starting Blenrep, you should talk to your doctor about your health history. The list has factors to consider.

Bleeding problems. Blenrep may cause low platelet levels. For people who have bleeding disorders, the drug may increase the risk of severe bleeding problems. This includes hemorrhage (serious internal bleeding). If you have a history of bleeding problems, tell your doctor. They’ll discuss whether Blenrep is safe for you.

Allergic reaction. If you’ve had an allergic reaction to Blenrep or any of its ingredients, your doctor will likely not prescribe Blenrep. Ask them what other medications are better options for you.

Alcohol use and Blenrep

It is not known if Blenrep has an interaction with alcohol. Ask your doctor how much you can drink during Blenrep treatment.

Pregnancy and breastfeeding while taking Blenrep

Blenrep is not safe to use during pregnancy because it can cause harm to a developing fetus. If you are pregnant, you will be given a test by your doctor.

Females* should use an effective form of birth control during treatment and for 4 months after their last dose of the drug. Males* with partners who can become pregnant should also use birth control during treatment and for 6 months afterward.

If you become pregnant while using Blenrep, tell your doctor. If you are planning a baby, let your doctor know. They will discuss other treatment options with you.

It is not known if Blenrep enters breast milk. You should not breast feed a child during Blenrep treatment. You should stop treatment after 3 months.

Ask your doctor about safer treatment options if you are currently breastfeeding.

* In this article, we use the terms “male” and “female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Blenrep is used in adults to treat multiple myeloma in certain situations.

Blenrep can cause mild and serious side effects. Ask your doctor questions about the drug, including its possible side effects, to help you decide whether Blenrep is a good treatment option.

There are a few questions you might want to ask.

  • What can I do to prevent side effects of Blenrep?
  • Is it possible that other medications can make my risk of side effects worse?
  • Will my side effects diminish as I continue treatment?


How can I reduce my risk of an infection?



Multiple myeloma is a type of cancer that affects your white blood cell levels. White blood cells help fight infections. So lower levels of these blood cells can make it harder for your immune system to work against an infection. Also, in studies of Blenrep, the drug was found to increase the risk of infections.

While you’re using Blenrep, your doctor will check your blood cell counts. If you have low white blood cell levels, your doctor will discuss whether you need treatment to improve these levels. Or they may recommend decreasing your dose of Blenrep, or temporarily or permanently stopping treatment with this drug.

A few things you can do to lower the risk of infection include regular handwashing, avoiding crowds, and not being in close contact with people who are sick.

If you have a cold or a sore throat, tell your doctor. They will likely order tests to check for infections. They will treat your infection.

Talk to your doctor about the risks of Blenrep and other ways to lower them.

The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

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.