Drug · FAERS side-effect profile with label screen
Natalizumab side effects: what 180,630 FDA adverse event reports show
Drug class
FDA label (Established Pharmacologic Class) · compare the class
Brand names
Tysabri
openFDA label
Who reports
180,630 reports · 31% serious · 5,103 with death outcome · 77% female
openFDA FAERS counts, all years, deduplication not applied
Used for
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 ) ].
FDA label, Indications and Usage
What it is
Natalizumab is a recombinant humanized IgG4κ monoclonal antibody produced in murine myeloma cells. Natalizumab contains human framework regions and the complementarity-determining regions of a murine antibody that binds to α4-integrin.
FDA label, Description section
Boxed warning
PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY TYSABRI increases the risk of progressive multifocal leukoencephalopathy (PML), an opportunistic viral infection of the brain that usually leads to death or severe disability.
FDA label
How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation.
Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)?
That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.
Causality screen of the 40 strongest signals
Labeled — boxed warning 1Labeled adverse reaction 2Labeled (related wording) 7Likely indication confounding 5Reporting / coding artifact 1Lab value / disease marker 4Not in label — unassessed 20
What the badges mean
- Labeled — boxed warning The term (or its clinical synonym) appears in the FDA boxed warning: causality is regulator-recognised and considered serious.
- Labeled adverse reaction The exact term appears in the label's warnings or adverse-reactions sections: a known, expected effect. The FAERS signal confirms the label rather than discovering anything.
- Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
- Likely indication confounding The term appears in the label's indications: reports probably describe the disease being treated (or its progression), not a drug effect. Classic confounding by indication.
- Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
- Lab value / disease marker A laboratory result, investigation or disease-activity marker (antibody positive, CRP abnormal, swollen joint count) not described in the label. These usually mirror the monitored disease or testing protocol rather than a drug effect; not screened further.
- Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.
Strongest disproportionality signals
Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only (and, for the 300 most-reported drugs, adjusted for age band), and flags pairs whose reports are unusually skewed by sex or come mostly from consumers. Each row also shows the PRR against the other drugs of the same FDA class, which removes most confounding by the condition being treated, and a calibrated p-value: on validation, known non-causes average an ROR of about 2, so significance is judged against that empirical null (✓ = p < 0.05 after calibration). 1,191 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
Show:
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Drug delivery device implantation | 121 | 138.7 106.4–180.9ROR 138.8 · calibrated p 2e-8 ✓ | 62.4 EB05 53.6 · IC025 +5.3 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=110 | not reported in cached trials |
| Jc virus test positive | 372 | 89.8 78.4–102.9ROR 90.0 · calibrated p 3e-7 ✓ | 50.5 EB05 46.3 · IC025 +5.4 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Lab value / disease marker | serious n=69 | not reported in cached trials |
| Agraphia | 198 | 56.9 48.0–67.5ROR 57.0 · calibrated p 7e-6 ✓ | 38.1 EB05 33.9 · IC025 +4.9 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=24 · 90% consumer | not reported in cached trials |
| Neutralising antibodies positive | 131 | 54.5 44.2–67.1ROR 54.5 · calibrated p 1e-5 ✓ | 36.9 EB05 31.9 · IC025 +4.7 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Lab value / disease marker | serious n=30 | not reported in cached trials |
| Infusion site haematoma | 137 | 48.6 39.8–59.4ROR 48.6 · calibrated p 2e-5 ✓ | 34.2 EB05 29.6 · IC025 +4.7 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | 100% consumer | NCT01416181: 1/439 (0.2%) on Natalizumab; 1/449 (0.2%) control (serious AE) |
| General symptom | 2,192 | 47.4 45.1–49.8ROR 47.9 · calibrated p 2e-5 ✓ | 33.7 EB05 32.5 · IC025 +5.0 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 38.1 (33.2–43.7) | Labeled (related wording) related wording | serious n=324 · 70% consumer | not reported in cached trials |
| Neuromyelitis optica | 97 | 46.7 36.8–59.1ROR 46.7 · calibrated p 3e-5 ✓ | 33.2 EB05 28.0 · IC025 +4.5 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=76 | not reported in cached trials |
| Loss of control of legs | 1,065 | 44.6 41.6–47.9ROR 44.9 · calibrated p 3e-5 ✓ | 32.3 EB05 30.7 · IC025 +4.9 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=283 · 83% consumer | not reported in cached trials |
| Opportunistic infection | 494 | 42.0 37.9–46.5ROR 42.1 · calibrated p 4e-5 ✓ | 30.9 EB05 28.7 · IC025 +4.8 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Labeled adverse reaction exact term | serious n=488 · 96% clinician | not reported in cached trials |
| Secondary progressive multiple sclerosis | 502 | 41.6 37.6–46.1ROR 41.7 · calibrated p 4e-5 ✓ | 30.7 EB05 28.5 · IC025 +4.8 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Likely indication confounding term in indications; also in warnings | serious n=215 | NCT01416181: 1/449 (0.2%) control (serious AE) |
| Progressive multifocal leukoencephalopathy | 2,127 | 40.1 38.2–42.1ROR 40.6 · calibrated p 5e-5 ✓ | 29.9 EB05 28.8 · IC025 +4.8 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Labeled — boxed warning exact term | serious PRR 55.3 · 93% clinician | NCT00297232: 18/1,094 (1.6%) on Natalizumab (serious AE) |
| Multiple sclerosis relapse | 16,902 | 37.4 36.8–38.0ROR 41.1 · calibrated p 4e-5 ✓ | 28.4 EB05 28.0 · IC025 +4.8 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 2,103.1 (1,479.0–2,990.7) | Labeled (related wording) related wording | age-adj. PRR 25.0 · serious PRR 31.9 | NCT00297232: 21/1,094 (1.9%) on Natalizumab (serious AE) |
| Immune reconstitution inflammatory syndrome | 1,182 | 35.7 33.4–38.1ROR 35.9 · calibrated p 1e-4 ✓ | 27.4 EB05 26.1 · IC025 +4.7 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Labeled adverse reaction exact term | serious n=1,177 · 95% clinician | NCT00297232: 11/1,094 (1.0%) on Natalizumab (serious AE) |
| Nuclear magnetic resonance imaging abnormal | 789 | 35.4 32.7–38.4ROR 35.6 · calibrated p 1e-4 ✓ | 27.2 EB05 25.7 · IC025 +4.6 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Reporting / coding artifact | serious n=161 | not reported in cached trials |
| Multiple sclerosis | 9,774 | 29.5 28.8–30.1ROR 31.1 · calibrated p 2e-4 ✓ | 23.6 EB05 23.2 · IC025 +4.5 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 267.4 (226.6–315.6) | Likely indication confounding term in indications; also in warnings | serious PRR 20.5 · 70% consumer | NCT00297232: 21/1,094 (1.9%) on Natalizumab (serious AE) |
| Progressive multiple sclerosis | 233 | 28.7 24.8–33.1ROR 28.7 · calibrated p 4e-4 ✓ | 23.0 EB05 20.7 · IC025 +4.2 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Likely indication confounding term in indications; also in warnings | serious n=79 | NCT01416181: 1/449 (0.2%) control (serious AE) |
| Primary progressive multiple sclerosis | 96 | 28.5 22.8–35.7ROR 28.5 · calibrated p 4e-4 ✓ | 22.9 EB05 19.3 · IC025 +4.0 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Likely indication confounding term in indications; also in warnings | serious n=28 | NCT01416181: 1/449 (0.2%) control (serious AE) |
| Poor venous access | 2,039 | 28.4 27.1–29.8ROR 28.7 · calibrated p 3e-4 ✓ | 22.9 EB05 22.1 · IC025 +4.4 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 7.0 (6.6–7.6) | Not in label — unassessed | serious n=192 · 76% consumer | not reported in cached trials |
| Multiple sclerosis pseudo relapse | 57 | 24.1 18.1–32.0ROR 24.1 · calibrated p 0.001 ✓ | 19.9 EB05 15.9 · IC025 +3.7 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Labeled (related wording) related wording | serious n=47 · 100% consumer | not reported in cached trials |
| Band sensation | 220 | 24.0 20.7–27.7ROR 24.0 · calibrated p 9e-4 ✓ | 19.9 EB05 17.8 · IC025 +4.0 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=48 · 85% consumer | not reported in cached trials |
| Paternal exposure before pregnancy | 50 | 23.0 17.0–31.1ROR 23.0 · calibrated p 0.001 ✓ | 19.1 EB05 15.1 · IC025 +3.6 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=49 · ♀ 100% (drug 77%) · 100% consumer | not reported in cached trials |
| Drug specific antibody present | 992 | 20.8 19.5–22.3ROR 20.9 · calibrated p 0.002 ✓ | 17.7 EB05 16.8 · IC025 +4.0 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 13.6 (11.9–15.5) | Lab value / disease marker | serious n=248 | not reported in cached trials |
| Peroneal nerve palsy | 771 | 18.1 16.8–19.5ROR 18.2 · calibrated p 0.003 ✓ | 15.7 EB05 14.8 · IC025 +3.8 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=148 · 83% consumer | not reported in cached trials |
| Sensation of heaviness | 527 | 17.8 16.3–19.5ROR 17.9 · calibrated p 0.003 ✓ | 15.5 EB05 14.5 · IC025 +3.8 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=36 · 87% consumer | not reported in cached trials |
| Hemianaesthesia | 104 | 17.0 13.9–20.9ROR 17.0 · calibrated p 0.004 ✓ | 14.9 EB05 12.6 · IC025 +3.5 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=46 · 77% consumer | not reported in cached trials |
| Hemihypoaesthesia | 43 | 17.0 12.3–23.4ROR 17.0 · calibrated p 0.005 ✓ | 14.7 EB05 11.3 · IC025 +3.2 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=24 · 100% consumer | not reported in cached trials |
| Relapsing-remitting multiple sclerosis | 110 | 16.8 13.8–20.6ROR 16.8 · calibrated p 0.005 ✓ | 14.7 EB05 12.5 · IC025 +3.5 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Likely indication confounding term in indications; also in warnings | serious n=80 | not reported in cached trials |
| Antibody test positive | 210 | 16.5 14.2–19.0ROR 16.5 · calibrated p 0.005 ✓ | 14.5 EB05 12.9 · IC025 +3.6 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Lab value / disease marker | serious n=24 · 76% consumer | not reported in cached trials |
| Vein disorder | 618 | 16.1 14.8–17.5ROR 16.1 · calibrated p 0.005 ✓ | 14.2 EB05 13.3 · IC025 +3.7 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=108 · 83% consumer | NCT00297232: 2/1,094 (0.2%) on Natalizumab (serious AE) |
| Central nervous system lesion | 1,674 | 15.9 15.1–16.7ROR 16.0 · calibrated p 0.005 ✓ | 14.0 EB05 13.5 · IC025 +3.7 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 269.1 (179.9–402.5) | Labeled (related wording) related wording | serious PRR 12.0 · 77% consumer | not reported in cached trials |
| Prescribed underdose | 2,349 | 15.4 14.7–16.1ROR 15.6 · calibrated p 0.006 ✓ | 13.7 EB05 13.2 · IC025 +3.7 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 32.2 (28.5–36.5) | Not in label — unassessed | age-adj. PRR 13.9 · serious PRR 18.0 | not reported in cached trials |
| Frustration | 401 | 14.3 12.9–15.9ROR 14.3 · calibrated p 0.009 ✓ | 12.8 EB05 11.8 · IC025 +3.5 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | 89% consumer | not reported in cached trials |
| Muscle spasticity | 1,323 | 13.8 13.0–14.6ROR 13.8 · calibrated p 0.010 ✓ | 12.4 EB05 11.8 · IC025 +3.5 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 255.2 (164.1–396.7) | Not in label — unassessed | serious PRR 9.9 · 71% consumer | NCT01416181: 2/439 (0.5%) on Natalizumab (serious AE) |
| Neurogenic bladder | 211 | 12.7 11.0–14.7ROR 12.8 · calibrated p 0.014 ✓ | 11.5 EB05 10.2 · IC025 +3.3 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=155 | NCT00297232: 1/1,094 (0.1%) on Natalizumab (serious AE) |
| Conjunctivitis infective | 41 | 12.7 9.2–17.6ROR 12.7 · calibrated p 0.016 ✓ | 11.1 EB05 8.4 · IC025 +2.8 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | ♀ 100% (drug 77%) · 100% consumer | not reported in cached trials |
| Infusion site bruising | 202 | 12.1 10.5–14.0ROR 12.1 · calibrated p 0.017 ✓ | 10.9 EB05 9.7 · IC025 +3.2 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 13.0 (9.7–17.3) | Labeled (related wording) related wording | 100% consumer | not reported in cached trials |
| Trigeminal neuralgia | 380 | 12.0 10.8–13.3ROR 12.0 · calibrated p 0.017 ✓ | 10.9 EB05 10.0 · IC025 +3.3 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious n=176 | NCT00297232: 2/1,094 (0.2%) on Natalizumab (serious AE) |
| Musculoskeletal disorder | 1,750 | 11.6 11.0–12.2ROR 11.7 · calibrated p 0.018 ✓ | 10.6 EB05 10.2 · IC025 +3.3 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 259.6 (176.3–382.3) | Labeled (related wording) related wording | serious PRR 6.6 · 84% consumer | NCT00297232: 1/1,094 (0.1%) on Natalizumab (serious AE) |
| Coordination abnormal | 1,227 | 11.0 10.4–11.7ROR 11.1 · calibrated p 0.022 ✓ | 10.1 EB05 9.7 · IC025 +3.2 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 591.6 (295.2–1,185.5) | Labeled (related wording) related wording | age-adj. PRR 7.7 · serious PRR 3.8 · 84% consumer | not reported in cached trials |
| Optic neuritis | 793 | 11.0 10.2–11.8ROR 11.0 · calibrated p 0.023 ✓ | 10.1 EB05 9.5 · IC025 +3.2 3/3 methods agree vs other Integrin Receptor Antagonists: only this drug | Not in label — unassessed | serious PRR 7.8 · 70% consumer | NCT01416181: 2/449 (0.4%) control (serious AE) |
Clinical concept groups
MedDRA splits one clinical problem across several terms (e.g. "neutropenia", "neutrophil count decreased", "agranulocytosis"), which dilutes term-level signals. These rows count reports with any term in a concept group (an exact union, not a sum), compared with all other drugs. Groups are hand-built and listed in the methods.
| Concept | Reports | PRR 95% CI | Reading |
|---|---|---|---|
| Opportunistic infection | 4,228 | 3.73.6–3.8 | signal |
| Fall / fracture | 8,238 | 2.52.5–2.6 | signal |
| Depression | 4,157 | 1.71.7–1.8 | raised |
| Serious infection | 11,095 | 1.71.6–1.7 | raised |
| Seizure | 2,538 | 1.51.4–1.6 | raised |
| Anaphylaxis / angioedema | 800 | 0.70.7–0.8 | lower than other drugs |
| Venous thromboembolism | 1,244 | 0.70.6–0.7 | lower than other drugs |
| Malignancy | 2,049 | 0.60.6–0.7 | lower than other drugs |
| Tendon disorder | 191 | 0.60.5–0.7 | lower than other drugs |
| Liver injury | 1,244 | 0.50.5–0.5 | lower than other drugs |
| Stroke | 874 | 0.40.4–0.4 | lower than other drugs |
| Anaemia | 987 | 0.40.4–0.4 | lower than other drugs |
| Hyperglycaemia / diabetes | 1,132 | 0.40.4–0.4 | lower than other drugs |
| Suicidality | 797 | 0.40.3–0.4 | lower than other drugs |
| Pancreatitis | 257 | 0.40.3–0.4 | lower than other drugs |
| Myocardial infarction | 608 | 0.30.3–0.4 | lower than other drugs |
Trial evidence (ClinicalTrials.gov)
✓ Trial adverse-event data found on ClinicalTrials.gov
Largest completed trials with posted results that list Natalizumab as a study intervention. The right-hand column of the signal table shows whether each FAERS term was also recorded in these trials, with a real denominator (14 of 40 signal terms matched).
- NCT00297232 — Natalizumab (Tysabri) Re-Initiation of Dosing (N=1094, PHASE3; 242 AE terms posted; arms: Natalizumab)
- NCT01416181 — A Clinical Study of the Efficacy of Natalizumab on Reducing Disability Progression in Participants With Second (N=889, PHASE3; 172 AE terms posted; arms: Placebo; Natalizumab 300 mg)
Caveats: trial populations, doses and follow-up differ from the reporting population; AE terms are sponsor-coded and matched here by wording; absence from a trial list means the term was not reported above the sponsor's frequency threshold, not that it cannot occur.
Most frequently reported reactions
By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Fatigue (tiredness) | 19,583 | 3.0 2.9–3.0ROR 3.2 · calibrated p 0.560 | 2.9 EB05 2.9 · IC025 +1.5 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 12.0 (11.7–12.3) | Labeled adverse reaction exact term | age-adj. PRR 2.7 · serious PRR 1.2 · 88% consumer | NCT00297232: 1/1,094 (0.1%) on Natalizumab (serious AE) |
| Multiple sclerosis relapse | 16,902 | 37.4 36.8–38.0ROR 41.1 · calibrated p 4e-5 ✓ | 28.4 EB05 28.0 · IC025 +4.8 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 2,103.1 (1,479.0–2,990.7) | Labeled (related wording) related wording | age-adj. PRR 25.0 · serious PRR 31.9 | NCT00297232: 21/1,094 (1.9%) on Natalizumab (serious AE) |
| Headache | 9,978 | 1.9 1.8–1.9ROR 1.9 · calibrated p 0.896 | 1.8 EB05 1.8 · IC025 +0.9 vs other Integrin Receptor Antagonists: PRR 9.3 (9.0–9.7) | Labeled adverse reaction exact term | age-adj. PRR 1.6 · serious PRR 1.1 · 83% consumer | NCT00297232: 1/1,094 (0.1%) on Natalizumab (serious AE) |
| Multiple sclerosis | 9,774 | 29.5 28.8–30.1ROR 31.1 · calibrated p 2e-4 ✓ | 23.6 EB05 23.2 · IC025 +4.5 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 267.4 (226.6–315.6) | Likely indication confounding term in indications; also in warnings | serious PRR 20.5 · 70% consumer | NCT00297232: 21/1,094 (1.9%) on Natalizumab (serious AE) |
| Gait disturbance | 9,496 | 6.0 5.9–6.1ROR 6.3 · calibrated p 0.134 | 5.7 EB05 5.6 · IC025 +2.5 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 54.1 (50.1–58.4) | Not in label — unassessed | age-adj. PRR 5.3 · serious PRR 3.1 · 84% consumer | NCT01416181: 2/439 (0.5%) on Natalizumab; 1/449 (0.2%) control (serious AE) |
| Fall | 8,039 | 2.9 2.8–2.9ROR 2.9 · calibrated p 0.647 | 2.8 EB05 2.8 · IC025 +1.5 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 21.6 (20.5–22.9) | Not in label — unassessed | age-adj. PRR 3.9 · serious PRR 2.6 · 72% consumer | NCT00297232: 7/1,094 (0.6%) on Natalizumab (serious AE) |
| Asthenia (weakness) | 8,005 | 2.5 2.4–2.6ROR 2.6 · calibrated p 0.783 | 2.5 EB05 2.4 · IC025 +1.3 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 13.2 (12.6–13.8) | Not in label — unassessed | age-adj. PRR 2.5 · serious PRR 1.5 · 78% consumer | NCT01416181: 2/439 (0.5%) on Natalizumab (serious AE) |
| Memory impairment | 7,957 | 7.1 6.9–7.2ROR 7.3 · calibrated p 0.086 | 6.7 EB05 6.6 · IC025 +2.7 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 44.0 (40.8–47.4) | Labeled (related wording) related wording | age-adj. PRR 5.1 · serious PRR 3.4 · 88% consumer | not reported in cached trials |
| Malaise (feeling unwell) | 7,408 | 2.0 1.9–2.0ROR 2.0 · calibrated p 0.951 | 2.0 EB05 1.9 · IC025 +0.9 vs other Integrin Receptor Antagonists: PRR 6.6 (6.4–6.8) | Not in label — unassessed | age-adj. PRR 1.7 · serious PRR 0.9 | not reported in cached trials |
| Drug ineffective (drug did not work) | 6,905 | 0.6 0.6–0.6ROR 0.6 · calibrated p 0.081 | 0.6 EB05 0.6 · IC025 -0.8 PRR-only: not supported by EBGM or IC vs other Integrin Receptor Antagonists: PRR 2.7 (2.6–2.8) | Reporting / coding artifact | age-adj. PRR 0.6 · serious PRR 0.5 | not reported in cached trials |
| Urinary tract infection (bladder infection) | 6,314 | 4.4 4.3–4.5ROR 4.6 · calibrated p 0.288 | 4.3 EB05 4.2 · IC025 +2.1 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 20.5 (19.3–21.7) | Labeled adverse reaction exact term | age-adj. PRR 5.0 · serious PRR 4.8 | NCT00297232: 13/1,094 (1.2%) on Natalizumab (serious AE) |
| Pain | 5,977 | 1.1 1.1–1.2ROR 1.1 · calibrated p 0.395 | 1.1 EB05 1.1 · IC025 +0.1 vs other Integrin Receptor Antagonists: PRR 8.5 (8.2–8.9) | Labeled adverse reaction exact term | age-adj. PRR 1.0 · serious PRR 0.8 · 81% consumer | NCT00297232: 2/1,094 (0.2%) on Natalizumab (serious AE) |
| Balance disorder | 5,687 | 8.1 7.9–8.3ROR 8.3 · calibrated p 0.059 | 7.6 EB05 7.5 · IC025 +2.9 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 93.0 (81.7–105.8) | Not in label — unassessed | age-adj. PRR 7.8 · serious PRR 3.8 · 81% consumer | not reported in cached trials |
| Hypoaesthesia (numbness) | 5,427 | 4.3 4.2–4.4ROR 4.4 · calibrated p 0.307 | 4.2 EB05 4.1 · IC025 +2.0 3/3 methods agree vs other Integrin Receptor Antagonists: PRR 21.8 (20.4–23.3) | Not in label — unassessed | age-adj. PRR 3.1 · serious PRR 2.5 · 83% consumer | not reported in cached trials |
| Pain in extremity | 4,934 | 2.0 1.9–2.0ROR 2.0 · calibrated p 0.934 | 1.9 EB05 1.9 · IC025 +0.9 vs other Integrin Receptor Antagonists: PRR 11.5 (10.9–12.1) | Labeled adverse reaction exact term | age-adj. PRR 1.8 · serious PRR 1.2 · 85% consumer | NCT00297232: 62/1,094 (5.7%) on Natalizumab |
Unlabeled candidate signals
These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.
- Drug delivery device implantation — n=121, PRR 138.7
- Agraphia — n=198, PRR 56.9
- Infusion site haematoma — n=137, PRR 48.6 (also seen in trial arm)
- Neuromyelitis optica — n=97, PRR 46.7
- Loss of control of legs — n=1,065, PRR 44.6
- Poor venous access — n=2,039, PRR 28.4
- Band sensation — n=220, PRR 24.0
- Paternal exposure before pregnancy — n=50, PRR 23.0
- Peroneal nerve palsy — n=771, PRR 18.1
- Sensation of heaviness — n=527, PRR 17.8
✓ A hand-written Bradford Hill causality assessment exists for this drug: Natalizumab ↔ Progressive multifocal leukoencephalopathy.
Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.
Common questions
What are the most reported side effects of Natalizumab?
In FDA FAERS, the most frequently co-reported reaction terms for Natalizumab are fatigue, multiple sclerosis relapse, headache, multiple sclerosis, gait disturbance, fall. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.
Does Natalizumab have an FDA boxed warning?
Yes. The current FDA label carries a boxed warning: PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY TYSABRI increases the risk of progressive multifocal leukoencephalopathy (PML), an opportunistic viral infection of the brain that usually leads to death or severe disability.
Do FAERS signals prove that Natalizumab causes these side effects?
No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.
Sources & methods
- FDA label via openFDA (set ID c5fdde91-1989-4dd2-9129-4f3323ea2962, effective 20250321; matched on
openfda.generic_name.exact:"NATALIZUMAB" AND openfda.product_type:"HUMAN PRESCRIPTION DRUG") - Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
- FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA
count=aggregation, fieldpatient.drug.openfda.generic_name.exact, 1,231 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction - Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
- Seriousness and sex counts from openFDA
count=serious,patient.patientsex,seriousnessdeath - ClinicalTrials.gov API v2 (query
NATALIZUMAB, results-bearing studies sorted by enrollment)
Page generated 2026-10-14. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.