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CD20 monoclonal antibodies subcutaneous solution (20 mg/0.4 mL)

Ofatumumab (subcutaneous)

Generic name: ofatumumab (subcutaneous)

Brand names: Kesimpta

Last updated November 3, 2026 0 views
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What is ofatumumab?

Ofatumumab is used to treat relapsing forms of multiple sclerosis in adults (including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease).

Ofatumumab may also be used for reasons not mentioned in this medication guide.

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Warnings

You may get infections more easily, including serious or fatal infections. Call your doctor if you have flu symptoms, a cough, night sweats, neck stiffness, confusion, or vision problems.

Ofatumumab may cause a brain infection that can lead to disability or death. Call your doctor if you have problems with speech, thinking, vision, or muscle movement.

If you've had hepatitis B, it may come back or worsen. Tell your doctor if you don't feel well and have pain in the upper right side of your stomach, vomiting, loss of appetite, or yellowing of your skin or eyes.

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Before taking this medicine

You should not use ofatumumab if you are allergic to it, or if you have:

  • an active hepatitis B infection.

Tell your doctor if you have ever had:

  • an active or chronic infection;
  • a condition for which you have used an immunosuppressant medication; or
  • hepatitis B.

Make sure you are up to date on all vaccines before you start using ofatumumab. Tell your doctor if you have received any vaccines in the past 2 weeks or if you are scheduled for a booster dose.

May harm an unborn baby. You may need a pregnancy test to ensure you are not pregnant. Use effective birth control while using ofatumumab and for at least 6 months after your last dose. Tell your doctor if you are pregnant or plan to become pregnant.

If you are pregnant, your name may be included in a pregnancy registry to monitor the effects of ofatumumab on the baby.

Ask a doctor if it is safe to breastfeed while using ofatumumab.

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Ofatumumab side effects

Get emergency medical help if you notice signs of an allergic reaction: hives, difficulty breathing, or swelling of your face, lips, tongue, or throat.

Some side effects may happen during the injection. Inform your medical caregivers if you feel dizzy, nauseous, light-headed, itchy, sweaty, or have a headache, chest tightness, back pain, trouble breathing, or swelling in your face.

Ofatumumab may lead to a brain infection that can cause disability or death. Inform your doctor if you have issues with speech, thought, vision, or muscle movement. These symptoms can worsen quickly.

Ofatumumab may cause serious side effects. Call your doctor immediately if you experience:

  • an active or chronic infection, including hepatitis B;
  • pain or burning when you urinate;
  • pain, redness, swelling, or itching at the injection site; or
  • right-sided upper stomach pain, vomiting, loss of appetite, yellowing of your skin or eyes, and feeling unwell.

Your cancer treatments may be delayed or stopped permanently if you have certain side effects.

Common side effects of ofatumumab may include:

  • bruising, swelling, warmth, redness, oozing, or bleeding at the injection site;
  • fever, cold symptoms such as stuffy nose, sneezing, sore throat;
  • cough, chest tightness, trouble breathing, lung infection; or
  • headache, tiredness, muscle aches.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

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How should I use ofatumumab?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Your doctor will perform tests to make sure ofatumumab is the right treatment for you.

Ofatumumab is injected under the skin, usually once per month. The first 3 doses are given weekly.

Ask your doctor or pharmacist if you don't understand how to use an injection.

Prepare an injection only when you are ready to give it. Call your pharmacist if the medicine looks cloudy, has changed colors or has particles in it.

Throw away a prefilled syringe after one use, even if there is still medicine left inside.

Do not reuse a needle or syringe. Place them in a puncture-proof "sharps" container and dispose of it following state or local laws. Keep out of the reach of children and pets.

Avoid injecting ofatumumab into scars, moles, or stretch marks, or into skin that is red, bruised, scaly, hard, or tender.

Your blood will be tested before, during, and after treatment with ofatumumab, and your next dose may be delayed based on the results.

You may be given medication to prevent certain side effects.

Store this medicine in the original container in the refrigerator away from light, do not freeze. Do not shake the medicine.

Ofatumumab can be stored at room temperature for up to 7 days. If not used, the medicine should be returned to the refrigerator and used within 7 days. Throw away any medicine not used within that time.

What happens if I miss a dose?

Use the medicine as soon as you remember, and then return to your normal schedule. Do not use two doses at the same time.

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What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

You should not get a vaccine while using ofatumumab.

This section was rewritten for readability and reviewed for meaning.

What other drugs will affect ofatumumab?

Tell your doctor about all your other medicines, especially:

  • drugs that weaken the immune system such as cancer medicine, steroids, and medicines to prevent organ transplant rejection.

This list is not complete. Other drugs may affect ofatumumab, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Find detailed information on biosimilars for this medication.

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Common questions about ofatumumab

How is Arzerra administered and how long to work?
Arzerra (ofatumumab) was administered by an intravenous infusion. Arzerra has now been discontinued. Continue reading

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Before you take this medicine: the information on this page is general and may not cover your personal circumstances. Read the label supplied with your medicine and ask a pharmacist or doctor if you are unsure, especially if you are pregnant, breastfeeding, taking other medicines or managing a long-term condition.
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Content is provided for education and is not medical advice. See our medical disclaimer.