Ofatumumab Injection (Multiple Sclerosis)

Brand Name(s): Kesimpta®

WHY is this medicine prescribed?

Ofatumumab injection is used to prevent episodes of symptoms and slow the worsening of disability in adults who have relapsing forms of multiple sclerosis (MS; a disease in which the nerves do not function properly and people may experience weakness, numbness, loss of muscle coordination, and problems with vision, speech, and bladder control), including:

  • clinically isolated syndrome (CIS; first nerve symptom episode that lasts at least 24 hours),
  • relapsing-remitting disease (course of disease where symptoms flare up from time to time), and
  • active secondary progressive disease (later stage of disease with continuous worsening of symptoms).

Ofatumumab is in a class of medications called monoclonal antibodies. It works by stopping certain cells of the immune system from reaching the brain and spinal cord and causing damage.

Ofatumumab is also available as an injection (Arzerra) that is used to treat chronic lymphocytic leukemia (a slowly developing cancer in which too many of a certain type of white blood cell accumulates in the body). This monograph only gives information about ofatumumab injection (Kesimpta) for multiple sclerosis. If you are receiving ofatumumab for chronic lymphocytic leukemia, read the monograph entitled Ofatumumab Injection (Chronic Lymphocytic Leukemia).

HOW should this medicine be used?

Ofatumumab injection comes as a solution (liquid) in a prefilled dosing pen and a prefilled syringe to inject subcutaneously (under the skin) into your stomach, thigh, or upper arm. It is usually injected once a week for the first 3 doses and then once monthly starting at week 4 of treatment for as long as your doctor recommends that you receive treatment. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Use ofatumumab injection exactly as directed. Do not inject more or less of it or inject it more often than prescribed by your doctor.

You will receive your first subcutaneous dose of ofatumumab injection in your doctor's office. After that, your doctor may allow you to inject ofatumumab yourself or have a caregiver perform the injections. Before you use ofatumumab injection yourself the first time, read the written instructions that come with it. Ask your doctor or pharmacist to show you or the person who will be injecting the medication how to inject it.

Inject ofatumumab into the thigh or stomach area, except the area 2 inches (5 centimeters) around your navel. If someone else is giving you the injection, that person can also inject the medication into your upper arms. Use a different site for each injection to reduce the chances of soreness or redness. Do not inject into an area where the skin is tender, bruised, red, or hard or where you have scars, moles, or stretch marks.

Remove the prefilled dosing pens or prefilled syringes from the refrigerator 15 to 30 minutes before your are ready to inject the medication. Do not remove the needle cover from the prefilled syringe while waiting for it to reach room temperature. Check to be sure that the expiration date printed on the package has not passed. The liquid should be clear and colorless to slightly brownish-yellow and should not be cloudy or discolored or contain particles. Call your pharmacist if there are any problems and do not inject the medication.

Do not shake the dosing pen or syringe. Be careful not to drop the medication onto a hard surface because this may damage the syringe or needle.

Never reuse or share dosing pens or syringes. Dispose of pens and syringes in a puncture-resistant container. Ask your doctor or pharmacist how to dispose of the puncture resistant container.

You may experience a reaction after you inject ofatumumab, usually within 24 hours after your injection. This reaction is most likely to occur after your first injection, but could happen at any time during your treatment. If you experience any of the following symptoms during or after your injection, tell your doctor immediately: bruising, pain, redness, swelling, or tenderness at the injection site; fever; headache; muscle pain; chills; or tiredness.

Are there OTHER USES for this medicine?

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What SPECIAL PRECAUTIONS should I follow?

Before receiving ofatumumab,

  • tell your doctor and pharmacist if you are allergic to ofatumumab, any other medications, or any of the ingredients in ofatumumab injection. Ask your pharmacist or check the Medication Guide for a list of the ingredients.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take while receiving ofatumumab injection. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • tell your doctor if you have or have ever had hepatitis B infection (swelling of the liver caused by a virus). Your doctor will probably tell you not to use ofatumumab injection.
  • tell your doctor if you have any medical conditions.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. You should use birth control during your treatment with ofatumumab injection and for 6 months after the final dose. If you become pregnant while receiving ofatumumab, call your doctor immediately. Ofatumumab injection may harm the fetus.
  • check with your doctor to see if you need to receive any vaccinations before receiving ofatumumab. Tell your doctor if you have received a vaccine within the past 4 weeks. Do not have any vaccinations without talking to your doctor during your treatment.
  • using ofatumumab injection may decrease your ability to fight infection and increase the risk that you will get a serious or life-threatening infection, including severe viral, bacterial, or fungal infections that spread throughout the body. Tell your doctor if you have an infection now or if you have any signs of infection such as fever, chills, or flu-like symptoms. If you experience any of the following symptoms during your treatment with ofatumumab, call your doctor: fever; chills; cough; flu-like symptoms; painful, difficult, or frequent urination; or other signs of infection.

What SPECIAL DIETARY instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do IF I FORGET to take a dose?

If you miss a dose during the first 3 weeks of treatment, talk to your doctor. If you miss a monthly ofatumumab injection, inject it as soon as possible and then continue giving your doses a month apart.

What SIDE EFFECTS can this medicine cause?

Ofatumumab may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • back pain

    Some side effects can be serious. If you experience any of these symptoms or those in the SPECIAL PRECAUTIONS section, call your doctor immediately or get emergency medical treatment:

  • weakness on one side of body or clumsiness of limb, new or sudden changes in thinking, confusion, dizziness, loss of balance, difficulty talking or walking, personality changes, or new or sudden changes in vision
  • rash; hives; trouble breathing; swelling of the face, eyelids, lips, mouth, tongue and throat; feeling faint; or chest tightness

Ofatumumab injection may cause other side effects. Call your doctor if you have any unusual problems while receiving this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online ( or by phone (1-800-332-1088).

What should I know about STORAGE and DISPOSAL of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it in the refrigerator and away from light until the time of use; do not freeze.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach.

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website ( for more information if you do not have access to a take-back program.

What should I do in case of OVERDOSE?

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

What OTHER INFORMATION should I know?

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body's response to ofatumumab injection.

Do not let anyone else use your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS® Patient Medication Information™. © Copyright, 2024. The American Society of Health-System Pharmacists®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: May 20, 2024.
AHFS® Patient Medication Information™. © Copyright, 2024
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