If you have a type of cancer called multiple myeloma, your doctor might suggest Darzalex (daratumumab) as a treatment option for you. Along with other questions you may have about the drug, you could be wondering about its side effects.

Multiple myeloma is a disease that can be treated with a prescription medication. Depending on the situation, Darzalex can be used alone or with other multiple myeloma treatments. It may be given as a short course or a long term treatment.

Darzalex is a biologic drug (a drug made using living organisms). It’s a targeted therapy for cancer (a treatment that finds and attacks cancer cells). It’s also a form of immunotherapy (a treatment that helps your immune system attack cancer cells).

Darzalex and Darzalex Faspro are the two forms of Darzalex.

  • A healthcare professional gives Darzalex by intravenous (IV) infusion in a doctor’s office or clinic. An IV infusion is an injection into a vein that’s given over a period of time. Infusions of Darzalex take 3 to 7 hours.
  • Darzalex Faspro contains an extra ingredient called hyaluronidase-fihj. A healthcare professional gives this form of Darzalex by subcutaneous injection. This is an injection under your skin, and it takes about 3 to 5 minutes.

The article focuses on the side effects of Darzalex. The FAQ section below explains the differences between the two forms of Darzalex.

For more information about Darzalex, including details about how it’s used, see this in-depth article.

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

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

Some people may experience side effects during their treatment. Some of the reported side effects of Darzalex include:

There are other side effects from Darzalex. Read on to find out more.

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

Mild side effects have been reported with Darzalex.

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

“These side effects should be temporary. Some may be easy to manage. If you have any symptoms that bother you, talk to your doctor or pharmacist. Unless your doctor recommends it, don’t stop using Darzalex.”

Darzalex may cause mild side effects other than the ones listed above. See the Darzalex patient 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 Darzalex, visit MedWatch.

There have been serious side effects reported with Darzalex.

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

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

Here are the answers to questions about Darzalex.

How long do the side effects of Darzalex last?

The side effects of Darzalex tend to go away in a few days or weeks. If you have side effects that last longer, talk to your doctor.

Some serious side effects of Darzalex, such as infusion-related reactions, can decrease quickly with treatment. But others may last a long time, even with treatment. How long side effects last will depend on how they respond to any treatments you have for them.

If you have questions about how long Darzalex side effects last, talk to your doctor.

How do the side effects of a Darzalex IV infusion compare with those of a Darzalex Faspro subcutaneous injection?

Darzalex is given by intravenous (IV) infusion, while Darzalex Faspro is given by subcutaneous injection. An IV infusion is an injection into a vein that’s given over a period of time. A subcutaneous injection is an injection given under your skin.

Both Darzalex and Darzalex Faspro can cause allergic reactions, including infusion reactions. These can happen during or shortly after the infusion or injection. These reactions are described in the “Side effects explained” section below.

The reactions are more common with Darzalex injections. You will be given medication to reduce your risk of having a reaction before you receive either form of Darzalex.

Mild skin reactions can be caused by Darzalex Faspro. There can be redness or a change in skin color.

For more information about Darzalex Faspro’s side effects, you can see the drug’s patient information.

Are there other differences between the side effects that Darzalex and Darzalex Faspro can cause?

When Darzalex and Darzalex Faspro are used to treat multiple myeloma, they have very similar side effects. These are described above and below.

However, Darzalex Faspro is also used to treat another condition called light chain amyloidosis. When it’s used for this condition, Darzalex Faspro may cause serious or even fatal heart problems. Darzalex isn’t used for this condition, so it’s not known if it can cause this side effect.

Talk to your doctor or pharmacist about the side effects of Darzalex and Darzalex Faspro.

Can Darzalex cause cardiac problems?

Yes, Darzalex can sometimes cause cardiac (heart) problems when it’s used to treat multiple myeloma. In studies of Darzalex, a type of irregular heartbeat called atrial fibrillation (AFib) was reported in some people.

There are symptoms of AFib.

If you have any of these symptoms, you should contact your doctor.

How long does Darzalex stay in your system?

After you stop taking Darzalex, it stays in your body for a while.

The amount of time it takes for the body to eliminate half a dose of the drug is the half-life. It takes a few years for the body to eliminate a drug from its system. The half-life of Darzalex is 18 days. Your doctor or pharmacist can give you more information.

Because of how long Darzalex stays in your system, you should talk with your doctor about using birth control during and after Darzalex treatment. For more information, see “Pregnancy and breastfeeding while taking Darzalex” in the “Warnings for Darzalex” section below.

There are some side effects that Darzalex may cause.

Infusion reaction

You’ll receive Darzalex as an intravenous (IV) infusion. An IV infusion is an injection into a vein that’s given over a period of time.

It’s possible to have a reaction to a Darzalex infusion. In fact, infusion reactions were one of the more common side effects reported in studies of Darzalex.

Infusion reactions are allergic reactions that happen during or shortly after an infusion of Darzalex. But it’s also possible to have a delayed reaction up to 3 days after the infusion.

Inflammation can be mild or severe. They may be fatal on rare occasions.

The first dose of Darzalex is most likely to cause these reactions. You are less likely to have this side effect with subsequent doses.

Symptoms can be caused by Darzalex reactions.

What might help

You will receive medication to reduce your risk of reactions. You will usually be given a combination.

  • diphenhydramine is an anti-allergic drug.
  • a corticosteroid, such as methylprednisolone or dexamethasone, to reduce inflammation (swelling)
  • acetaminophen to reduce There is a high degree of There is a high degree of There is a high degree of There is a high degree of fever….

The day after your Darzalex injection, you will be given corticosteroids to reduce your risk of reactions.

The first infusion will be given over 7 hours to lower your risk of reactions. Your infusions can be given for 3 to 5 hours after this.

A healthcare professional will be watching you. If you have a mild or moderate reaction, they may stop your infusion. They will restart the infusion at a slower rate after your symptoms have gone away. You get the medication more slowly.

If you have a life threatening reaction, your doctor may stop your Darzalex treatment.

“If you have a delayed reaction after leaving your doctor’s office, call your doctor. If you think you are having a medical emergency, call the emergency number.”

For additional information about dosing for Darzalex, you can visit this article.

Low blood cell counts

Low blood cell counts are caused by Darzalex. You may have low levels of blood cells while you are receiving treatment with Darzalex.

A low level of neutrophils (a type of white blood cell) is called neutropenia. White blood cells help your body fight germs that can cause infections. If you have neutropenia with Darzalex, you may have an increased risk of infections. Symptoms of infections can include:

A low level of red blood cells is called anemia. Red blood cells carry oxygen throughout your body. If you have anemia with Darzalex, you may have symptoms such as:

A low level of platelets is called thrombocytopenia. Platelets help your blood clot after an injury. If you have thrombocytopenia with Darzalex, you may have symptoms such as:

  • It was bruise easily.
  • bleeding, such as nosebleeds or bleeding gums
  • It takes longer to stop bleeding.

What might help

Your doctor will check your blood cells frequently. If you have low blood cell counts, tell your doctor right away.

If you have low blood cell counts, your doctor may delay your next Darzalex injection.

Respiratory infections

You may get respiratory infections while you’re having treatment with Darzalex. In fact, upper respiratory infections, such as colds, were commonly reported in studies of the drug.

Respiratory infections are typically mild, but they can sometimes become more serious and affect your lungs. Serious infections, such as the flu, bronchitis, and pneumonia, have been reported in people taking Darzalex.

There are symptoms of serious respiratory infections.

  • cough
  • coughing up blood or phlegm
  • The breath was very thin.
  • There is chest pain.
  • There is a high degree of There is a high degree of There is a high degree of There is a high degree of fever….
  • It is cold.
  • There is a lack of energy.

What might help

You can help protect yourself from respiratory infections while you are having Darzalex treatment.

Before you start receiving Darzalex, talk with your doctor about getting vaccines, such as the flu shot, COVID-19 vaccine, or pneumonia vaccine.

If you get a cold during your treatment, talk to your doctor or pharmacist. If your symptoms are bad, they can recommend over-the-counter treatments.

“If the symptoms don’t get better after a few days, you should see your doctor. You may need to take medication to stop the infection from getting worse.”

If you have a respiratory problem, you should contact your doctor. You will need medication to treat the problem.

Peripheral sensory neuropathy

Darzalex can sometimes cause a side effect called peripheral sensory neuropathy. This is nerve damage that causes tingling or burning sensations, numbness, or pain in your hands or feet.

In studies of Darzalex, peripheral sensory neuropathy was one of the more commonly reported side effects.

What might help

If you have peripheral sensory neuropathy, you should talk to your doctor. They can suggest ways to manage this side effect.

For example, if you have troublesome pain in your hands or feet, your doctor may prescribe medication to help with this. They may suggest a numbing cream or patch to put directly on the area where you’re having pain. Or they may prescribe certain antidepressants or seizure medications that are also used for nerve pain.

Other treatments that may be helpful for this nerve problem include physical therapy, acupuncture, and electrical nerve stimulation. Your doctor can tell you more about these treatments.

Here are some other tips to help.

  • Sometimes hot and cold temperatures can cause a problem. If you are in this situation, you should avoid hot baths or showers. You may want to keep your feet and hands warm.
  • “If you have numbness, it can lead to injuries. Take care of your hands and feet, and make sure you don’t have any injuries.”
  • If you have the disease in your feet, you should always wear shoes that protect your whole foot. Make sure that your shoes are not too tight.
  • If the neuropathy is in your hands, you should take extra care when using sharp objects.

Allergic reaction

Some people can have an allergic reaction to Darzalex.

Mild or serious symptoms can be included.

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

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. To manage your symptoms, they may suggest an over-the-counter antihistamine that you take by mouth, such as Benadryl (diphenhydramine). Or they may recommend a product that you apply to your skin, such as hydrocortisone cream.

If your doctor confirms that you had a mild allergic reaction to Darzalex, 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 that you had a serious allergic reaction to Darzalex, they may have you switch to a different treatment.

Keeping track of side effects

Keep notes about any side effects you have during your Darzalex 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 after starting that dose did you experience side effects?
  • Specific symptoms from the side effect.
  • How did it affect your daily activities?
  • You were also taking other medications.
  • Other information is important to you.

Sharing your notes with your doctor will help them learn more about how Darzalex affects you. Your doctor can use this information to adjust your treatment plan.

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

History of hepatitis B. If you’ve had hepatitis B in the past, Darzalex could make this infection active again in your body. Before you start Darzalex treatment, your doctor will test you for the hepatitis B virus (HBV). If you test positive, your doctor will check for signs of HBV becoming active during and after your Darzalex treatment.

History of chickenpox or shingles. Chickenpox and shingles are caused by the herpes zoster virus. If you’ve had either infection in the past, Darzalex could make the virus flare up in your body. This can cause shingles. If you’ve had chickenpox or shingles, your doctor may prescribe antiviral medication to prevent shingles while you have Darzalex.

Allergic reaction. If you’ve had an allergic reaction to Darzalex or any of its ingredients, you shouldn’t have this treatment. Ask your doctor what other medications are better options for you.

Chronic obstructive pulmonary disease (COPD). COPD is a long-term lung condition that causes breathing problems. If you have COPD, you may need extra medications to help your breathing. Your doctor may prescribe extra inhalers to open your airways or corticosteroids to reduce swelling in your lungs.

Eye-related conditions. If you’re taking Darzalex, you could develop eye-related conditions. Darzalex can cause myopia (nearsightedness) or a There is fluid in the eye.. Increased fluid can raise eye pressure and may also lead to There is a problem with the eye., a condition that can cause optic nerve damage and vision loss. If you experience headaches, tired eyes, or blurred vision, or if you have a history of eye problems, tell your doctor.

Alcohol use and Darzalex

Alcohol isn’t known to interact with Darzalex. But it’s recommended that you avoid drinking alcohol the day before and after your infusions. That’s because alcohol can make you dehydrated. It’s important to stay hydrated before, during, and after your infusions. This is because Darzalex can cause dehydration as well.

You may have to take precautions with Darzalex if you have alcohol. Nausea, sputum, or tiredness are included.

If you have questions about drinking alcohol while you are having treatment, talk to your doctor.

Pregnancy and breastfeeding while taking Darzalex

“Darzalex can cause fetal development problems, so it isn’t safe to take during pregnancy. If you are pregnant or planning to become pregnant, you should tell your doctor before you start Darzalex treatment.”

If you’re able to become pregnant, it’s recommended that you use birth control during treatment and for 3 months after your last dose of the drug.

It is not known if Darzalex can be used in breast milk. It is not recommended that you feed your baby while having this treatment. If you are planning to breastfeeding or taking Darzalex, you should talk to your doctor about the best way to feed your child while taking it.

Darzalex can cause side effects. Mild and easily managed, but serious side effects are also possible. Your doctor will watch you for any side effects that may occur during your treatment.

If you want to know more about the possible side effects of Darzalex, you should talk to your doctor. They can help you decide if this medication is a good choice for you.

Questions you might ask include:

  • Is it safe to use Darzalex if I have asthma?
  • Do side effects get more common if Darzalex is used with other drugs?
  • Will I need to monitor side effects?
  • Does Darzalex increase my risk of getting Covid-19?


What should I do if Darzalex causes me to vomit?



If you develop diarrhea while taking Darzalex, let your doctor know. They may recommend an over-the-counter medication such as Imodium (loperamide) to manage your diarrhea. They may also suggest that you try a diet of bland foods, such as bananas, white rice, applesauce, and toast.

You should also make sure to drink plenty of fluids while you have diarrhea. This can help prevent dehydration, which is also a possible side effect of Darzalex.

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.