Tysabri (natalizumab) is a prescription drug that’s used to manage Crohn’s disease and certain kinds of multiple sclerosis (MS). The drug comes as an intravenous (IV) infusion. It’s usually given every 4 weeks.

Tysabri is used in adults to treat:

The active ingredient in Tysabri is natalizumab. (An active ingredient is what makes a drug work.) Tysabri is a biologic drug, which means it’s made from living cells.

You’ll receive Tysabri as an intravenous (IV) infusion (an injection into your vein given over time). Tysabri belongs to a group of drugs called integrin receptor antagonists.

This article describes the dosage of Tysabri infusions, as well as its strength and how it’s given. To learn more about Tysabri, see this in-depth article.

You’ll receive Tysabri doses at an infusion center that’s certified to administer this drug. For more information, see the “How is Tysabri given?” section below. Your doctor will explain Tysabri’s typical dosing schedule and other information about the infusion doses.

What is Tysabri’s form?

Tysabri comes as a liquid solution in a single-dose vial. You’ll receive the drug as an intravenous (IV) infusion (an injection into a vein given over a period of time). Tysabri infusions take about 1 hour.

What strength does Tysabri come in?

Tysabri comes as 300 milligrams (mg) per 15 milliliters (mL) of solution.

What are the usual dosages of Tysabri?

The information below describes dosages that are commonly recommended.

Dosage for multiple sclerosis (MS), clinically isolated syndrome, and Crohn’s disease

Tysabri’s recommended dosage is 300 mg, given by IV infusion every 4 weeks.

In some cases, your doctor may suggest extended dosing for you. This would change your dosing frequency so that you receive Tysabri once every 6 to 8 weeks.

It’s important to note that extended dosing for Tysabri is not approved by the FDA. This is considered off-label dosing. (With off-label dosing, a doctor prescribes a dosage other than the FDA-approved dosage.)

Extended dosing may be done to lower your risk of developing progressive multifocal leukoencephalopathy (PML).* But more studies are needed to determine whether extended dosing could lower PML risk and still be effective at managing your condition. To learn more about extended dosing, talk with your doctor. And see the “Ask a pharmacist” section below.

* Tysabri has a boxed warning for the risk of PML. To learn more, see the “Boxed warning” section at the beginning of this article.

Is Tysabri used long term?

Yes, Tysabri is usually used as 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. Your doctor will evaluate your treatment at certain points to determine whether you should keep receiving Tysabri.

If you have Crohn’s disease, your doctor will likely have you stop Tysabri treatment if the drug hasn’t been effective after 12 weeks.

You’ll receive Tysabri as an intravenous (IV) infusion (an injection into a vein given over a period of time.) The infusion typically lasts 1 hour. You’ll also be monitored for 1 hour after your infusion for at least the first 12 infusions to make sure you don’t have a reaction to Tysabri.

Tysabri is only given at certain clinics that are certified through a Risk Mitigation and Evaluation Strategy (REMS) prescribing program called TOUCH. This is because of serious risks of progressive multifocal leukoencephalopathy (PML)* with the drug.

Your doctor can provide more information about treatment centers where you can receive Tysabri. You can also learn more on the manufacturer’s website.

* Tysabri has a boxed warning for the risk of PML. To learn more, see the “Boxed warning” section at the beginning of this article.

It’s important to keep all of your appointments to receive doses of Tysabri. But if you miss an appointment, call the clinic as soon as you remember. They’ll set up your appointment so you can receive the missed dose. They can also adjust your future appointments as needed to keep you on track with your treatment plan.

If you need help remembering your appointment for your dose of Tysabri, try using a medication reminder. This can include setting an alarm or downloading a reminder app on your phone.

The sections above describe the usual dosages provided by the drug’s manufacturer. If your doctor recommends Tysabri for you, they’ll prescribe the dosage that’s right for you.

If you have questions or concerns about your current dosage, talk with your doctor.

Here are some examples of questions you may want to ask your doctor:

  • Does receiving a drug through an intravenous (IV) infusion raise my risk of side effects?
  • Would a different dosage of Tysabri lower my chances of side effects?
  • Should my dosage change if Tysabri isn’t working for my condition?

To learn more about Tysabri, see these articles:

To get information on different conditions and tips for improving your health, subscribe to any of Healthline’s newsletters. You may also want to check out the online communities at Bezzy. It’s a place where people with certain conditions can find support and connect with others.

Q:

Could extended dosing (receiving Tysabri less often) lower my risk of progressive multifocal leukoencephalopathy (PML)?

Anonymous

A:

It’s possible. Whether extended dosing lowers your risk of PML may depend on several factors. They include how severe your condition is, your genetics, and how well Tysabri clears from your body. PML is a rare but serious side effect of Tysabri, and the drug has a boxed warning about the risk of PML. To learn more, see the “Boxed warning” section at the beginning of the article.

It’s important to note that extended dosing for Tysabri is not approved by the FDA. This is considered off-label dosing. (With off-label dosing, a doctor prescribes a dosage other than the FDA-approved dosage.)

A few studies have reported benefits of extending Tysabri dosing from every 4 weeks to every 6 or 8 weeks when used for MS. It’s thought that this may lower the risk of developing PML. But other studies haven’t found this to be the case. More studies are needed to determine whether extended dosing could lower PML risk and still be effective at managing multiple sclerosis or Crohn’s disease.

If you’re concerned about the risk of PML with Tysabri, talk with your doctor before starting treatment.

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.