Skip to Content


Generic Name: natalizumab (nat ta LIZ yoo mab)
Brand Name: Tysabri

Medically reviewed on October 16, 2017

What is natalizumab?

Natalizumab is a monoclonal antibody that affects the actions of the body's immune system. Monoclonal antibodies are made to target and destroy only certain cells in the body. This may help to protect healthy cells from damage.

Natalizumab is used to treat relapsing forms of multiple sclerosis.

Natalizumab is also used to treat moderate to severe Crohn's disease in adults. It is usually given after other medicines have been tried without success.

Natalizumab may also be used for purposes not listed in this medication guide.

Important Information

Natalizumab may cause serious viral infections of the brain or spinal cord that can lead to disability or death. Call your doctor right away if you have a sudden fever, severe headache, confusion, memory problems, vision changes, eye pain, weakness on one side of your body, or problems with using your arms or legs. These symptoms may start gradually and get worse quickly.

Before taking this medicine

Natalizumab may cause a serious brain infection called progressive multifocal leukoencephalopathy (PML). This infection may be more likely if you use natalizumab for longer than 2 years, if you have used an immunosuppressant drug in the past, or if you have been infected with John Cunningham Virus (JCV).

You should not receive natalizumab if you are allergic to it, or if you have ever had PML.

Natalizumab is available only from a certified pharmacy under a special program called the TOUCH Prescribing Program. You must be registered in the program and understand the risks and benefits of taking this medicine.

To make sure natalizumab is safe for you, tell your doctor if you have ever had:

It is not known whether this medicine will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

Natalizumab can pass into breast milk, but effects on the nursing baby are not known. Tell your doctor if you are breast-feeding.

Natalizumab is not approved for use by anyone younger than 18 years old.

How is natalizumab given?

Before your first dose, your doctor may recommend an MRI to make sure you do not have any signs of a brain infection.

Natalizumab is injected into a vein through an IV. A healthcare provider will give you this injection. Natalizumab is usually given once every 4 weeks.

Natalizumab must be given slowly and the IV infusion can take at least 1 hour to complete. You will be watched closely for at least 1 hour after receiving natalizumab, to make sure you do not have an allergic reaction to the medication. An allergic reaction can occur up to 2 hours or longer after your infusion.

Natalizumab can weaken your immune system. While using natalizumab, you may need frequent blood tests. You may also need a brain scan or spinal tap (lumbar puncture) if you develop signs of a brain infection.

It is extremely important that your doctor check you every 3 to 6 months for signs of serious infection. Your doctor may also want to check you for several weeks after you stop using natalizumab.

Tell any doctor who treats you that you are using natalizumab.

What happens if I miss a dose?

Call your doctor for instructions if you miss an appointment for your natalizumab injection.

What happens if I overdose?

Since this medicine is given by a healthcare professional in a medical setting, an overdose is unlikely to occur.

What should I avoid while receiving natalizumab?

Avoid being near people who are sick or have infections. Tell your doctor at once if you develop signs of infection.

Natalizumab side effects

Get emergency medical help if you have signs of an allergic reaction: hives, rash; wheezing, difficult breathing; swelling of your face, lips, tongue, or throat.

Some allergic reactions may occur during the injection. Tell your caregiver right away if you feel dizzy, nauseated, light-headed, itchy, cold, sweaty, or if you have chest pain, trouble breathing, or swelling in your face.

Natalizumab may cause serious viral infections of the brain or spinal cord that can lead to disability or death. Call your doctor right away if you have any of the following symptoms during treatment with natalizumab or up to 6 months after your last dose (these symptoms may start gradually and get worse quickly):

  • sudden fever or severe headache;

  • confusion, memory problems, or other changes in your mental state;

  • weakness on one side of your body;

  • vision changes, eye pain or redness;

  • problems with speech or walking; or

  • trouble using your arms and legs.

Also call your doctor at once if you have:

  • fever, chills, cough with yellow or green mucus;

  • pain or burning when you urinate; or

  • liver problems--nausea, upper stomach pain, itching, tiredness, loss of appetite, dark urine, clay-colored stools, or jaundice (yellowing of the skin or eyes).

Common side effects may include:

  • headache, tired feeling;

  • nausea, diarrhea, stomach pain;

  • cold symptoms such as stuffy nose, sneezing, sore throat;

  • joint pain, pain in your arms and legs; or

  • vaginal itching or discharge.

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.

See also: Side effects (in more detail)

What other drugs will affect natalizumab?

Tell your doctor about all your current medicines and any you start or stop using, especially drugs that weaken the immune system such as cancer medicine, steroids, and medicines to prevent organ transplant rejection.

Other drugs may interact with natalizumab, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.