Drugs › Integrin receptor antagonist
Brand name · Natalizumab
Tysabri: adverse event reports filed with FDA
173,350 reports list it as a suspect or interacting product, 2005–2026. Class: Integrin receptor antagonist.
- 173,350
- reports as suspect product
- 0.8% of all reports · about 8,098 a year
- 2,471
- reports, 12 months to June 2026
- 2,865 in the 12 months before
- 30.8%
- marked serious by the reporter
- 48.8% across the class
- 2.8%
- record death among outcomes, as reported
- 4,925 reports · not verified by FDA
Between February 2005 and June 2026, 173,350 adverse event reports received by FDA list the brand name Tysabri (natalizumab) as a suspect or interacting product. Reports that mention it only as a concomitant medication (4,677) are left out of every figure here.
In the 12 months to June 2026, 2,471 reports listed it, down 14% from 2,865 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Over its reporting history that is about 8,098 reports a year and 0.8% of the 20,646,523 reports in the database, and 67.2% of the reports for the integrin receptor antagonist class. How many people take it is not in the data, so a count is not a rate of occurrence.
The MedDRA terms listed most often are fatigue (10.8%), multiple sclerosis relapse (9.4%) and headache (5.4%). A report can list several reactions, so shares add to more than 100%; 3,548 different terms appear across these reports. Fatigue is recorded in 10.8% of these reports, about the same share as in the median integrin receptor antagonist drug (9.4%).
30.8% of the reports are marked serious by the reporter (48.8% across the class); 2.8% record death among the outcomes and 19.1% record hospitalisation, as reported. 66% of the reports came from consumers, and the largest patient age group is 45 to 64 (29.7%). FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event."
Reports by month, five years
Reports by the month FDA received them. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.
By year received
2026 covers reports received through June 2026 only.
Reactions recorded in the reports
share of Tysabri reports recording the termmedian drug in integrin receptor antagonist
- Fatiguetiredness10.8%18,807
- Multiple sclerosis relapsea flare of multiple sclerosis9.4%16,365
- Headachehead pain5.4%9,419
- Multiple sclerosis5.4%9,350
- Gait disturbancedifficulty walking5.1%8,890
- Memory impairmentmemory problems4.4%7,689
- Astheniaweakness or lack of energy4.4%7,604
- Falla fall4.4%7,572
- Malaisegeneral feeling of being unwell4.1%7,189
- Drug ineffectivethe medicine did not work as expected3.7%6,330
- Urinary tract infectionbladder or urinary infection3.5%6,020
- Painpain, site not specified3.3%5,668
- Balance disorderproblems with balance3.1%5,404
- Hypoaesthesianumbness3%5,163
- Pain in extremitypain in an arm or leg2.7%4,729
- Muscular weaknessmuscle weakness2.5%4,358
- Nasopharyngitisa cold2.5%4,356
- Nauseafeeling sick2.3%3,955
- Dizzinesslight-headedness or unsteadiness2.1%3,715
- Mobility decreasedreduced ability to move about2.1%3,650
- Stressstress2%3,489
- Cognitive disorderproblems with thinking or memory1.9%3,365
- Muscle spasmsmuscle cramps1.7%3,010
- Depressionlow mood1.7%2,969
- Arthralgiajoint pain1.7%2,913
- Hypersensitivityan allergic-type reaction1.6%2,798
- Feeling abnormalfeeling odd or not right1.6%2,789
- Visual impairmentreduced vision1.6%2,710
- Pyrexiafever1.6%2,693
- Anxietyanxiety1.5%2,633
Top 30 of 3,548 MedDRA preferred terms recorded across these reports, with a plain-language gloss where one is available. One report can record several terms. The hollow bar is the median share across the 4 drugs in the integrin receptor antagonist class; it describes the reports, not the patients. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."
Outcomes recorded
Outcome flags as the reporter set them; a report can carry several, and "other serious" is FDA's own category for serious reports outside the named outcomes. Grey bar: all 258,020 reports in the class. FDA has not verified any outcome and states that the reports "cannot be used to estimate the incidence of these events."
Patients and reporters
Patient age
Patient sex
Who reported
Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 90.9% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Multiple sclerosis | 155,837 | 89.9% |
| Relapsing-remitting multiple sclerosis | 3,941 | 2.3% |
| Crohn's disease | 840 | 0.5% |
| Crohn's disease | 673 | 0.4% |
| Maternal exposure timing unspecified | 532 | 0.3% |
| Secondary progressive multiple sclerosis | 129 | 0.1% |
The indication field is filled in by the reporter and is often blank; shares are of all 173,350 reports.
Drugs most often listed in the same reports
| Drug (any role in the report) | Reports | Share of Tysabri reports |
|---|---|---|
| Avonex | 20,987 | 12.1% |
| Ampyra | 3,006 | 1.7% |
| Baclofen | 2,823 | 1.6% |
| Tecfidera | 2,029 | 1.2% |
| Gabapentin | 1,545 | 0.9% |
| Vitamin d | 1,471 | 0.8% |
| Ergocalciferol | 1,106 | 0.6% |
| Copaxone | 1,009 | 0.6% |
| Lyrica | 817 | 0.5% |
| Aspirin | 744 | 0.4% |
Other products listed in reports where Tysabri is a suspect product, whatever their own role. Co-listing means the two were recorded together; it says nothing about either product's part in the event. Only the 2,500 most-reported names are counted here.
In context
| Measure | Tysabri | Integrin receptor antagonist | All reports |
|---|---|---|---|
| Reports as suspect product | 173,350 | 258,020 | 20,646,523 |
| Share of that pool | — | 67.2% | 0.8% |
| Reports, latest 12 months | 2,471 | — | 1,332,454 |
| Marked serious | 30.8% | 48.8% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 28 | 35 | 91 |
| Hospitalisation recorded, per 1,000 reports | 191 | 222 | 213 |
| Consumer-filed share | 66% | 61.5% | 45.8% |
| Top term, share of reports | Fatigue 10.8% | median 9.4% | 3.7% |
Shares are of reports, not of patients treated. The number of people taking a product is not in the data, so none of these figures is a rate, and differences between columns reflect who takes a product, who reports and how long it has been sold. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."
Other drugs in the integrin receptor antagonist class
| Drug | Name type | Reports | Latest 12 months | Marked serious |
|---|---|---|---|---|
| Vedolizumab | generic | 58,654 | 8,232 | 98.6% |
| Entyvio | brand | 23,511 | 2,171 | 57.5% |
| Natalizumab | generic | 2,505 | 65 | 48.7% |
Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." A brand and its generic are separate rows because reporters name them separately.
Questions about Tysabri reports
How many adverse event reports has FDA received for Tysabri?
173,350 reports list Tysabri as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 2,471 of them arrived in the latest 12 months. Another 4,677 list it only as a concomitant medication.
What reactions are recorded in Tysabri reports?
fatigue (10.8%), multiple sclerosis relapse (9.4%), headache (5.4%), multiple sclerosis (5.4%) and gait disturbance (5.1%). These are MedDRA preferred terms coded from what the reporter described; a report can list several, and a term's presence is not a finding that Tysabri was responsible.
How serious are the reports?
30.8% are marked serious by the reporter. Among the outcomes recorded, 2.8% of reports include death and 19.1% include hospitalisation. FDA has not verified these outcomes and states that the reports "cannot be used to estimate the incidence" of the events.
Who files these reports?
consumer or non-health professional (66%), other health professional (18.5%) and physician (14.3%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Tysabri rising?
2,471 reports in the 12 months to June 2026, down 14% from 2,865 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Counts also move with how many people take a product, its time on the market and publicity.
Do these reports show that Tysabri was responsible for these reactions?
No. FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event." The reaction may relate to the condition being treated, to other medicines, or to something else.
Is this a list of the side effects of Tysabri?
No. It is a count of what was reported to FDA. The adverse reactions observed in clinical studies are printed on the FDA-approved label, which a pharmacist or clinician can go through with you.
How do I report an adverse event?
Consumers and health professionals can report to FDA through MedWatch (Form FDA 3500 online, or 1-800-FDA-1088), or to the manufacturer, which must pass reports on. See the guide on how to report.
Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A report counts here when it lists Tysabri as a suspect or interacting product; reports listing it only as a concomitant medication (4,677) are excluded. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.
Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.