72/100 · Elevated
Manufactured by Biogen Inc.
Natalizumab Adverse Events: Significant Fatigue and Neurological Concerns
289,050 FDA adverse event reports analyzed
Last updated: 2026-05-12
NATALIZUMAB is a medication tracked in the FDA Adverse Event Reporting System (FAERS), manufactured by Biogen Inc.. Based on analysis of 289,050 FDA adverse event reports, NATALIZUMAB has a safety score of 72 out of 100. This score indicates a relatively favorable safety profile, with fewer or less severe adverse events compared to many other tracked medications. The most commonly reported adverse reactions for NATALIZUMAB include FATIGUE, MULTIPLE SCLEROSIS RELAPSE, HEADACHE, MULTIPLE SCLEROSIS, GAIT DISTURBANCE. This page provides a comprehensive breakdown of reported side effects, safety signals, patient demographics, and AI-powered safety analysis for NATALIZUMAB.
Natalizumab has a safety concern score of 72 out of 100, placing it in the elevated concern category based on analysis of FDA adverse event data. The FDA has received approximately 289,050 adverse event reports for this medication, which is primarily manufactured by Biogen Inc..
The most commonly reported adverse events include Fatigue, Multiple Sclerosis Relapse, Headache. Of classified reports, 31.1% were designated as serious by the FDA, meaning they involved hospitalization, disability, or other significant medical outcomes. Fatigue and multiple sclerosis relapse are the most common adverse events.
Neurological symptoms such as headache, gait disturbance, and cognitive disorder are frequently reported. Serious adverse events, including death and progressive multifocal leukoencephalopathy, are notable.
Patients taking Natalizumab should monitor for the commonly reported side effects and contact their healthcare provider if they experience any unusual symptoms. Natalizumab is contraindicated in patients with a history of progressive multifocal leukoencephalopathy. Regular monitoring for signs of infection is advised. This analysis is based on voluntary FDA adverse event reports and should not replace professional medical advice.
Natalizumab received a safety concern score of 72/100 (elevated concern). This is based on a 31.1% serious event ratio across 179,310 classified reports. The score accounts for 289,050 total adverse event reports and 100 distinct reaction types. This elevated score indicates a notable proportion of serious adverse events and warrants careful monitoring.
Adverse event reports by sex: Female: 135,988, Male: 40,466, Unknown: 259. The most frequently reported age groups are age 50 (3,467 reports), age 48 (3,422 reports), age 49 (3,393 reports). These demographics reflect reporting patterns and may not represent the full patient population.
Out of 179,310 classified reports for NATALIZUMAB:
The FDA classifies an adverse event as “serious” if it results in death, hospitalization, disability, congenital anomaly, or requires intervention to prevent permanent damage.
Demographics reflect voluntary FDA adverse event reporting patterns and may not represent the full patient population.
Natalizumab is contraindicated in patients with a history of progressive multifocal leukoencephalopathy. Regular monitoring for signs of infection is advised.
If you are taking Natalizumab, here are important things to know. The most commonly reported side effects include fatigue, multiple sclerosis relapse, headache, multiple sclerosis, gait disturbance. While many of these may be mild and temporary, you should contact your healthcare provider if any symptoms are severe or persistent. Monitor for signs of progressive multifocal leukoencephalopathy, especially in patients with a history of immunosuppression. Regularly review and adjust dosing as necessary to manage adverse events. If you experience a serious adverse reaction, seek emergency medical attention immediately or call 911. You can report side effects to the FDA's MedWatch program at 1-800-FDA-1088.
The FDA continues to monitor the safety of natalizumab, particularly for serious neurological and infectious adverse events. Patients should report any new or worsening symptoms to their healthcare provider immediately.
The FDA has received approximately 289,050 adverse event reports associated with Natalizumab. These reports come from healthcare professionals, consumers, and manufacturers through the FDA Adverse Event Reporting System (FAERS). Note that the number of reports does not directly indicate the frequency of side effects, as adverse events are voluntarily reported and may be underrepresented.
The most frequently reported adverse events for Natalizumab include Fatigue, Multiple Sclerosis Relapse, Headache, Multiple Sclerosis, Gait Disturbance. By volume, the top reported reactions are: Fatigue (19,460 reports), Multiple Sclerosis Relapse (16,794 reports), Headache (9,914 reports). These figures reflect FDA adverse event reports and may not represent the true incidence rate of these side effects in all patients taking Natalizumab.
Out of 179,310 classified reports, 55,808 (31.1%) were classified as serious and 123,502 as non-serious. The FDA classifies an event as "serious" if it results in death, hospitalization, disability, or other medically significant outcomes. A higher serious-event ratio warrants closer attention but does not necessarily mean the drug is unsafe.
Adverse event reports for Natalizumab break down by patient sex as follows: Female: 135,988, Male: 40,466, Unknown: 259. This distribution reflects reporting patterns rather than actual risk differences between groups. Reporting rates can be influenced by prescribing patterns, disease demographics, and reporting behavior.
The most frequently reported age groups for Natalizumab adverse events are: age 50: 3,467 reports, age 48: 3,422 reports, age 49: 3,393 reports, age 51: 3,352 reports, age 47: 3,345 reports. Age-related reporting patterns can reflect both the demographics of the patient population and potential age-related susceptibility to certain side effects.
The primary manufacturer associated with Natalizumab adverse event reports is Biogen Inc.. Multiple manufacturers may produce generic versions of this drug. The manufacturer listed reflects the most frequently reported brand in FDA adverse event data.
Beyond the most common reactions, other reported adverse events for Natalizumab include: Fall, Asthenia, Memory Impairment, Malaise, Drug Ineffective. Less common side effects can still be clinically significant. Patients should report any unusual symptoms to their healthcare provider.
You can report adverse events from Natalizumab to the FDA through their MedWatch program at www.fda.gov/medwatch, by calling 1-800-FDA-1088, or by completing Form FDA 3500. Healthcare professionals, consumers, and manufacturers can all submit reports. Reporting helps the FDA monitor drug safety after approval.
Natalizumab has a safety concern score of 72 out of 100 (elevated concern). This score is calculated from the ratio of serious to non-serious adverse events, the diversity of reported reactions, and the overall volume of reports relative to usage. Fatigue and multiple sclerosis relapse are the most common adverse events.
Key safety signals identified in Natalizumab's adverse event data include: High incidence of fatigue and multiple sclerosis relapse.. Multiple serious neurological adverse events, including progressive multifocal leukoencephalopathy.. Significant number of reports involving death and serious infections.. These signals are derived from patterns in FDA reports and should be discussed with a healthcare provider for personalized assessment.
Natalizumab is contraindicated in patients with a history of progressive multifocal leukoencephalopathy. Regular monitoring for signs of infection is advised. Always inform your healthcare provider about all medications, supplements, and over-the-counter drugs you are taking before starting Natalizumab.
Monitor for signs of progressive multifocal leukoencephalopathy, especially in patients with a history of immunosuppression. Regularly review and adjust dosing as necessary to manage adverse events.
Natalizumab has 289,050 adverse event reports on file with the FDA. Neurological symptoms such as headache, gait disturbance, and cognitive disorder are frequently reported. The volume of reports for Natalizumab reflects both the drug's usage level and the vigilance of the reporting community.
The FDA continues to monitor the safety of natalizumab, particularly for serious neurological and infectious adverse events. Patients should report any new or worsening symptoms to their healthcare provider immediately. For the most current regulatory information, check the FDA's drug labeling database or consult your pharmacist.
Explore other medications manufactured by Biogen Inc. and compare their safety profiles:
The following drugs share commonly reported adverse reactions with NATALIZUMAB:
Drugs related to NATALIZUMAB based on therapeutic use, drug class, or shared indications: