Tysabri (natalizumab) is a brand-name prescription medication. The Food and Drug Administration (FDA) has approved it for use in adults to treat:

Tysabri belongs to a drug class called integrin receptor antagonists. Tysabri is a biologic medication. It’s not available in a biosimilar version.

Tysabri comes as a solution that’s given by a healthcare professional as an IV infusion.

For information about the Tysabri dosage for MS and Crohn’s disease, including the drug’s strength and how the medication is given, keep reading. For a comprehensive look at Tysabri, see this article.

* “Active” means that you currently have symptoms.

This article describes typical dosages for Tysabri provided by the drug’s manufacturer. However, your doctor will prescribe the Tysabri dosage that’s right for you.

Here’s some information on the dosage and administration of Tysabri for multiple sclerosis (MS) and Crohn’s disease.

Tysabri form

Tysabri comes as a solution in a single-dose vial that’s given as an IV infusion by a healthcare professional.

Tysabri strength

Tysabri comes in one strength: 300 milligrams (mg) per 15 milliliters (mL) of solution.

Typical dosage

The following information describes the infusion dosage that’s commonly prescribed or recommended. However, your doctor will determine the best dosage to fit your needs.

Tysabri dosage for all uses

The usual dosage of Tysabri is the same for all conditions it’s prescribed to treat.

For MS and Crohn’s disease, the typical Tysabri dosing frequency is 300 mg once every 4 weeks.

Long-term treatment

Tysabri is meant to be a long-term treatment. If you and your doctor determine that Tysabri is safe and effective for you, you’ll likely receive it long term.

Note that long-term treatment raises your risk of a serious side effect called progressive multifocal leukoencephalopathy (PML). Tysabri 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 boxed warning section at the start of this article.

It’s important to discuss the possible risks of extended dosing with your doctor. They can help you decide if receiving Tysabri long term is right for you.

Tysabri is given as an IV infusion by a healthcare professional. (An IV infusion is an injection given into a vein over time.) You’ll likely receive Tysabri infusions at your doctor’s office, a clinic, a hospital, or an infusion center once every 4 weeks.

Tysabri infusions typically last about 1 hour. Then a healthcare professional will also monitor you for at least 1 hour after your infusion has finished. This is to make sure you don’t have an allergic reaction to Tysabri.

If you’d like to know more about infusions with Tysabri, talk with your doctor.

If you miss an appointment to have your Tysabri infusion, call your doctor’s office right away to reschedule.

To help make sure that you don’t miss an appointment, put your dosing schedule on a calendar or try using a medication reminder. This can include setting an alarm or downloading a reminder app on your phone.

The dosages in this article are typical dosages provided by the drug manufacturer. If your doctor recommends Tysabri for you, they will prescribe the dosage that’s right for you. If you have questions about the dosage of Tysabri that’s right for you, talk with your doctor.

Besides learning about dosage, you may want other information about Tysabri. These additional articles might be helpful to you:

Disclaimer: Medical News Today 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.