If you have multiple sclerosis (MS) or Crohn’s disease, your doctor might prescribe Tysabri for you.

Tysabri is a prescription medication used to treat multiplesclerosis in adults.

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. It belongs to a group of drugs called integrin receptor antagonists. You’ll receive Tysabri through an intravenous (IV) infusion at a healthcare clinic. (An IV infusion is an injection into your vein given over a period of time.)

This article describes the dosage of Tysabri infusions, as well as its strength and how you’ll receive the drug. To learn more about Tysabri, see this in-depth article.

Note: This article covers Tysabri’s usual dosages provided by the drug’s manufacturer. But your doctor will prescribe the Tysabri dosage that’s right for you.

You will receive Tysabri at an approved center. The “How is Tysabri given?” section gives more information. Your doctor will explain Tysabri\’s typical schedule and how it works.

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.)

What strength does Tysabri come in?

300 milligrams per 15 mL of solution is the maximum amount of Tysabri that can be taken.

What are the usual dosages of Tysabri?

The information below is for dosages that are recommended.

Dosage for multiple sclerosis (MS) and Crohn’s disease

The common dose for the disease is 300mg of Tysabri every 4 weeks. Your doctor may suggest an extended dose for you, which will change your dose so that you receive Tysabri once every 6 to 8 weeks.

“The FDA does not approve extended dosing for Tysabri. This is not considered to be in line with the FDA’s guidelines. A doctor prescribes a different dosage than the FDA-approved one.”

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?

Tysabri is a long-term treatment. If you and your doctor determine that Tysabri is safe and effective for you, you will likely receive it for a long time. Your doctor will evaluate your treatment at certain points to determine if you should continue receiving Tysabri.

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 special 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 is important to keep appointments so you can get Tysabri. If you miss an appointment, call the clinic. They will set up your appointment so you can get the missed dose. They can change your future appointments to keep you on track.

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 dosages provided by the drug manufacturer are described in the sections above. If your doctor recommends Tysabri, they will prescribe the correct amount.

If you have questions about your current dose, talk to your doctor.

Some questions you may want to ask your doctor.

  • Does receiving a drug through an intravenous (IV) infusion raise my risk of side effects?
  • Is a different Tysabri dosage likely to lower my side effects?
  • “Should my dose be changed if Tysabri isn’t working?”

For more tips on managing your condition and treatment updates, subscribe to Healthline’s multiple sclerosis (MS) or inflammatory bowel disease (IBD) newsletters.

And if you’re looking for a supportive group of people with the same chronic condition as you, consider joining a Bezzy community. You’ll find an MS community and an IBD community that you can sign up for through the Bezzy homepage.

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, such as 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.

“The FDA does not approve extended dosing for Tysabri. This is not considered to be in line with the FDA’s guidelines. A doctor prescribes a different dosage than the FDA-approved one.”

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 are concerned about the risk of PML with Tysabri, you should talk to your doctor.

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.