Natalizumab Injection
Natalizumab injection (Tysabri) is used to treat relapsing forms of multiple sclerosis and moderately to severely active Crohn's disease.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 1 clinical label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
⚠️ FDA Boxed Warning — the FDA’s strongest safety alert ▾
Tysabri carries a serious boxed warning about a rare brain infection called progressive multifocal leukoencephalopathy (PML). PML is caused by the JC virus and usually leads to death or severe, permanent disability. This infection typically only strikes people whose immune systems are weakened. Three things raise your risk the most: testing positive for anti-JCV antibodies, taking Tysabri for a long time (especially beyond 2 years), and having used immunosuppressant drugs in the past. Because of this risk, Tysabri is only available through a special restricted program called the TOUCH Prescribing Program — you cannot get it at a regular pharmacy. Watch for new or worsening symptoms such as confusion, memory problems, weakness on one side of the body, vision changes, or trouble speaking or walking, and report them to your doctor immediately. If PML is suspected, Tysabri must be stopped right away.
📖 Natalizumab Injection: Patient Information Guide
A plain-language walkthrough of Natalizumab Injection — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.
🎯What it's used for▾
Natalizumab injection (Tysabri) is approved for two distinct conditions in adults:
- Relapsing multiple sclerosis (MS): Tysabri treats relapsing forms of MS — including clinically isolated syndrome, relapsing-remitting MS, and active secondary progressive MS — used alone (monotherapy) in adults.
- Crohn's disease (CD): Tysabri is used to bring on (induce) and sustain (maintain) remission in adults with moderately to severely active Crohn's disease who have not responded to, or cannot tolerate, standard CD therapies and TNF-alpha inhibitors. It must not be combined with immunosuppressants or TNF-alpha inhibitors in this setting.
⚙️How it works▾
Natalizumab is an integrin receptor antagonist — a type of targeted antibody that attaches to proteins called α4-integrins on the surface of immune cells. By blocking these integrins, it prevents inflammatory immune cells from sticking to blood vessel walls and crossing into sensitive tissue. In MS, this means fewer immune cells get through the blood-brain barrier to cause new lesions. In Crohn's disease, it reduces immune-cell migration into the inflamed gut lining by blocking a specific pathway involving the α4β7 integrin and its target receptor on gut blood vessels.
Because Tysabri works by dampening immune-cell traffic rather than broadly suppressing the entire immune system, it is more targeted than traditional immunosuppressants — but it still carries real immune-related risks, most importantly the risk of a serious brain infection called PML.
💊How it's taken▾
Tysabri is given as a slow intravenous (IV) infusion into a vein over approximately one hour, once every four weeks. It is not something you take at home — each infusion is administered in a clinical setting by a healthcare provider enrolled in the TOUCH Prescribing Program. Since it is given by IV, food intake has no bearing on dosing.
- In Crohn's disease, if there is no meaningful benefit after 12 weeks of treatment, Tysabri should be stopped.
- In Crohn's disease, if you are on long-term oral steroids when starting Tysabri, your doctor will plan a gradual steroid taper once Tysabri is working.
- Follow your prescriber's exact schedule — do not miss infusion appointments without consulting your care team.
🤒Side effects — in detail▾
The most common side effects reported with Tysabri include:
- Headache
- Fatigue
- Joint pain (arthralgia)
- Urinary tract infection
- Upper or lower respiratory infections
- Nausea
- Rash
- Depression
- Abdominal discomfort or diarrhea (mainly in MS patients)
- Gastroenteritis (stomach bug)
More serious reactions — including severe allergic reactions during or just after an infusion, signs of liver injury (yellowing skin, dark urine), unusual bruising or bleeding, or any new neurological symptoms — require immediate medical attention. PML and herpes infections of the brain or eye are rare but life-threatening risks that your care team will monitor for closely.
⚠️Warnings & precautions▾
- Progressive multifocal leukoencephalopathy (PML): This rare but usually fatal or severely disabling brain infection is the most critical risk. Risk is highest in people who are anti-JCV antibody positive, have used Tysabri for more than 2 years, or previously used immunosuppressant drugs. Tysabri must be stopped immediately if PML is suspected.
- Serious herpes infections: Life-threatening cases of herpes encephalitis (brain infection) and meningitis have occurred. Blindness from acute retinal necrosis (a herpes-related eye infection) has also been reported. Tysabri must be stopped if these occur.
- Liver injury: Significant liver damage, including cases requiring a liver transplant, has been reported. Tell your doctor immediately about any jaundice (yellow skin or eyes), dark urine, or severe stomach pain.
- Severe allergic reactions: Anaphylaxis and other serious hypersensitivity reactions can occur during or after infusion. Tysabri must be permanently stopped if this happens.
- Increased infection risk: Because Tysabri affects the immune system, it raises the risk of various infections. Report signs of new infection to your doctor promptly.
- Low platelets (thrombocytopenia): Tysabri can reduce platelet counts, increasing bleeding risk. Newborns of mothers who used Tysabri during pregnancy should have blood counts checked.
🔀What it interacts with▾
Tysabri has important interactions that can significantly raise your risk of serious infection:
- Immunosuppressants (e.g., azathioprine, methotrexate, cyclosporine, 6-mercaptopurine): Must not be used alongside Tysabri in Crohn's disease; MS patients on chronic immunosuppressants are generally not candidates for Tysabri — combining them greatly increases the risk of PML and other serious infections.
- TNF-alpha inhibitors (e.g., infliximab): Must not be combined with Tysabri in Crohn's disease due to the heightened infection risk.
- Corticosteroids: In Crohn's disease, long-term steroid use with Tysabri is discouraged; a steroid taper should begin once Tysabri starts working.
- Aminosalicylates: These Crohn's disease medications may be continued safely alongside Tysabri.
This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.
📋Before taking it▾
- History of PML: Do not use Tysabri if you have ever had PML — it is contraindicated.
- Prior allergic reaction to Tysabri: Do not use it again if you previously had a serious hypersensitivity reaction to Tysabri.
- Anti-JCV antibody status: Testing positive raises your risk of PML significantly — especially the longer you are on Tysabri or if you previously used immunosuppressants. Discuss the risk-benefit balance carefully with your doctor.
- Pregnancy: Tysabri can harm a developing baby. Cases of low platelets and anemia in newborns have been reported. Newborns exposed to Tysabri in the womb should have a blood count (CBC) checked. Tell your doctor if you are pregnant or planning to become pregnant.
- Breastfeeding: Natalizumab has been detected in human milk. Talk to your doctor about the risks and benefits before breastfeeding while on Tysabri.
- Children and teenagers: Tysabri is not approved for anyone under 18 years of age.
- Older adults (65+): There is limited data in this age group; discuss any concerns with your prescriber.
- Kidney or liver problems: The pharmacokinetics of Tysabri in patients with kidney or liver insufficiency have not been studied; tell your doctor about any such conditions.
- TOUCH Program enrollment: Both you and your prescriber must be enrolled in the TOUCH Prescribing Program to access Tysabri.
🚑If you take too much▾
The safety of doses higher than the recommended 300 mg has not been adequately evaluated, and the maximum safe dose of Tysabri has not been determined. If an overdose is suspected, contact your healthcare provider or seek emergency medical care immediately.
📡Pharmacodynamics — effects in the body▾
After Tysabri is administered, it blocks immune cells from leaving the bloodstream and entering inflamed tissue. As a result, it causes a measurable increase in the number of circulating immune cells — including lymphocytes, monocytes, basophils, and eosinophils — because those cells can no longer exit the blood vessels as they normally would. Importantly, Tysabri does not affect the count of neutrophils (another type of immune cell) circulating in the blood.
🔬Pharmacokinetics — how your body processes it▾
In MS patients, Tysabri reaches steady-state blood levels (the point where the amount entering the body equals the amount leaving) after about 24 weeks of dosing every four weeks. Its half-life — the time it takes the body to clear half of the drug — is approximately 11 days in MS patients and about 10 days in Crohn's disease patients. Body weight has a modest effect on how quickly the drug is cleared; higher body weight leads to slightly faster clearance. If the body develops antibodies against natalizumab itself, the drug is cleared much faster — about three times faster in MS patients — which can reduce its effectiveness. The drug's behavior in people with kidney or liver problems has not been studied.
📦How to store it▾
refrigerated between 2°C to 8°C (36°F to 46°F). Protect from light. Store diluted TYSABRI solution refrigerated at 2°C to 8°C (36°F to 46°F)
📄 Written from Natalizumab Injection’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →
Supplements & herbs that interact with Natalizumab Injection
70 supplements and herbal products have documented interactions with Natalizumab Injection in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 1
- Moderate · 59
- Minor · 10
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
🩺 Pharmacist Counseling Corner
Quick, plain-English answers to the questions patients ask most about Natalizumab Injection — the kind of thing our pharmacy team would talk through with you at the counter.
Why do I have to go to a special program just to get this medication? ▾
What is PML and how would I know if I was getting it? ▾
How is Tysabri actually given, and what happens during an infusion visit? ▾
What side effects are most likely to happen? ▾
Can I take my other medications alongside Tysabri? ▾
Is it safe to use Tysabri if I'm pregnant or thinking about getting pregnant? ▾
Is Natalizumab Injection available over the counter? ▾
When was Natalizumab Injection first available? ▾
💬 Answers drafted from Natalizumab Injection’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →
🧰 Keep exploring
💊 How Natalizumab Injection comes
Natalizumab Injection is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Injection
How this form is used
- Tysabri is used as monotherapy to treat relapsing forms of multiple sclerosis in adults, including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease.
- Tysabri is used to induce and maintain clinical response and remission in adults with moderately to severely active Crohn's disease who have not responded to, or cannot tolerate, conventional therapies and TNF-alpha inhibitors.
- Tysabri is given as an intravenous infusion over approximately one hour, once every four weeks; it must not be given as a rapid IV push or bolus.
- Tysabri must be administered in a healthcare setting by a prescriber enrolled in the TOUCH Prescribing Program.
- Patients must be observed during every Tysabri infusion and for at least one hour afterward for the first 12 infusions; monitoring after the 13th infusion and beyond is guided by clinical judgment.
- Tysabri solution must be used within 48 hours of preparation and must never be frozen.
📊 Natalizumab Injection across the U.S. market
How Natalizumab Injection appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
📈 How widely Natalizumab Injection is used
A general measure of how commonly Natalizumab Injection is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Natalizumab Injection is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Natalizumab Injection prescribed? Of the 1,596 medications we measure, Natalizumab Injection ranks #868 by Medicaid prescriptions — more than 46% of them.
Utilization by Natalizumab Injection product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
15 ML natalizumab 20 MG/ML Injection
Summed across the 1 of 1 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 477484
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Natalizumab Injection, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 1 of 1 listed Natalizumab Injection NDCs with Medicaid activity.
🔍 Compare Natalizumab Injection products
A representative set of FDA-listed product records for Natalizumab Injection — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Injection | ||||
| 300 mg/15 mL | Intravenous | Biogen Inc. × 3 listings | BLA | View NDC → |
Showing 3 of 3 products — FDA National Drug Code Directory. See every product, package size and price: browse all 3 Natalizumab Injection NDCs →
📈 What people report — real-world data (FDA FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Natalizumab Injection — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Natalizumab Injection in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
🏛️ The road to your pharmacy
How Natalizumab Injection went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
🚨 Recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
Source: openFDA drug enforcement (recall) reports.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 354770 1 dose form · 2 strengths
-
Dose form (SCDF) Injection RxCUI 1656270In current FDA listingsClinical drug / strength (SCD) 15 ML natalizumab 20 MG/MLRxCUI 47748415 ML natalizumab-sztn 20 MG/MLRxCUI 2725173
Look up RxCUI 354770 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
📦 Supply & shortage status
Whether Natalizumab Injection is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
🏷️ Sold under these brand names
🏭 Manufacturers & labelers
RxNorm drug class
Natalizumab Injection belongs to the Integrin Receptor Antagonist class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
🔬 Where this comes from
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How we combine label and product data
HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 1 FDA-filed SPL label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.
Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. Biogen Inc. is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.
This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.