Tysabrinatalizumab
According to the FDA label: TYSABRI is an integrin receptor antagonist indicated for treatment of: Multiple Sclerosis (MS) TYSABRI is indicated as monotherapy for the treatment of relapsing forms of multiple sclerosis, to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease, in adults. TYSABRI increases the risk of PML [See Warnings and Precautions ( 5.1 ) ].
180,086 adverse event reports submitted to the FDA (2004–2026)
Top Reported Adverse Events
The most frequently reported events in association with Tysabri in the FAERS database. These are events reported by patients taking this medication, not necessarily caused by it. A single report may include multiple events.
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Fatigue 19,516 reports
Extreme tiredness or lack of energy that does not improve with rest.
Full definition in the glossary → See all drugs reporting this event →Multiple Sclerosis Relapse 16,845 reports
A return or worsening of multiple sclerosis symptoms. It often appears in reports as part of the condition being treated.
Full definition in the glossary →Headache 9,954 reports
Pain in the head or upper neck.
Full definition in the glossary → See all drugs reporting this event →Multiple Sclerosis 9,735 reports
A condition where the immune system affects the protective covering of nerves, which can disrupt movement and other functions. It often appears in reports as a condition being treated.
Full definition in the glossary →Gait Disturbance 9,488 reports
Difficulty walking normally, such as an unsteady or altered way of walking.
Full definition in the glossary →Fall 8,028 reports
A report that the person fell down. Falls are tracked because they can signal issues like dizziness, weakness, or balance problems.
Full definition in the glossary →Asthenia 8,001 reports
Physical weakness or lack of strength.
Full definition in the glossary →Memory Impairment 7,944 reports
Difficulty remembering things.
Full definition in the glossary → See all drugs reporting this event →Malaise 7,362 reports
A general feeling of being unwell or uncomfortable, without a specific symptom.
Full definition in the glossary →Drug Ineffective 6,899 reports
A report that the medication did not work as expected for the person taking it. This is a reporting category, not a sign the drug is defective. It simply means someone felt it was not helping their condition.
Full definition in the glossary →Urinary Tract Infection 6,296 reports
An infection in the bladder, urethra, or kidneys, often called a UTI.
Full definition in the glossary → See all drugs reporting this event →Pain 5,959 reports
A general report of physical discomfort, used when no more specific location is given.
Full definition in the glossary →Balance Disorder 5,677 reports
Difficulty staying steady, often with a feeling of unsteadiness or near-falling.
Full definition in the glossary →Hypoaesthesia 5,415 reports
Reduced sense of touch or numbness in part of the body. Also spelled hypoesthesia in American English.
Full definition in the glossary → See all drugs reporting this event →Pain in Extremity 4,921 reports
Pain in an arm or leg.
Full definition in the glossary →
Ranked by frequency of reports, not severity. The most-reported event is not necessarily the most dangerous or the most common in patients taking this drug.
Who Is Reporting
Demographics of patients in FAERS reports that included this information. Not all reports include patient demographics.
By Sex
View reporter sex data as a table
| Sex | Reports |
|---|---|
| Female | 136,526 |
| Male | 40,584 |
| Unknown | 259 |
By Age Group
View age group data as a table
| Age group | Reports |
|---|---|
| 0-17 | 913 |
| 18-34 | 20,084 |
| 35-49 | 44,728 |
| 50-64 | 37,358 |
| 65-74 | 5,296 |
| 75+ | 470 |
This shows who filed reports, reflecting who takes this drug and who tends to report, not who is at greatest risk.
Reported Outcomes
Outcomes recorded in FAERS reports that included Tysabri. A single report may involve multiple reactions, each with a different outcome. These categories are defined by FDA reporting guidelines, not by PillSignal.
View outcome data as a table
| Outcome | Reports |
|---|---|
| Non-Serious | 123,861 |
| Hospitalization | 34,473 |
| Other Serious | 22,370 |
| Death | 5,067 |
| Life-Threatening | 1,045 |
| Disability | 677 |
Serious outcomes are far more likely to be reported than mild ones, so this overstates how often outcomes are serious. A recorded death does not mean the drug caused it.
Report Volume Over Time
Number of FAERS reports received per quarter for Tysabri. Changes in volume may reflect shifts in prescribing rates, media attention, or reporting behavior, not changes in the medication's safety profile.
View report trend as a table
| Year | Reports |
|---|---|
| 2004 | 2 |
| 2005 | 1,355 |
| 2006 | 48 |
| 2007 | 559 |
| 2008 | 1,549 |
| 2009 | 2,555 |
| 2010 | 20,068 |
| 2011 | 25,661 |
| 2012 | 22,980 |
| 2013 | 29,497 |
| 2014 | 12,502 |
| 2015 | 7,069 |
| 2016 | 8,948 |
| 2017 | 8,570 |
| 2018 | 8,295 |
| 2019 | 6,205 |
| 2020 | 5,145 |
| 2021 | 3,965 |
| 2022 | 4,362 |
| 2023 | 3,971 |
| 2024 | 3,277 |
| 2025 | 2,831 |
| 2026 (partial) | 672 |
The steep increase around 2004 reflects the FDA's move to electronic submission, not a change in this drug's safety. Trends track reporting volume, not risk.
Medications commonly reported with Tysabri
In FDA adverse event reports that mention Tysabri, these medications appeared most often in the same report.
- Interferon Beta-1a (23,272 reports)
- Dalfampridine (5,002 reports)
- Baclofen (3,567 reports)
- Dimethyl (3,324 reports)
- Ergocalciferol (3,155 reports)
This reflects co-occurrence in submitted reports, not evidence of drug interaction or combined risk. People often report several medications taken for the same condition or for unrelated reasons. Talk to a doctor or pharmacist about your specific medications.
Related Drugs
Other medications with similar adverse event profiles in FDA FAERS reports.
Data Source
This data is sourced from the FDA's Adverse Event Monitoring System (AEMS), formerly FAERS, via the OpenFDA API. PillSignal is not affiliated with the FDA.
View this data on the FDA website →Data last updated: June 2026