Interferon Beta-1B side effects: what 19,059 FDA adverse event reports show
Drug class
Interferon beta
Brand names
Betaseron
Who reports
19,059 reports · 56% serious · 1,337 with death outcome · 78% female
Used for
BETASERON is indicated for the treatment of relapsing forms of multiple sclerosis (MS), to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease, in adults. BETASERON is an interferon beta indicated.
What it is
Interferon beta-1b is a purified, sterile, lyophilized protein product produced by recombinant DNA techniques. Interferon beta-1b is manufactured by bacterial fermentation of a strain of Escherichia coli that bears a genetically engineered plasmid containing the gene for human interferon betaser17.
Boxed warning
None in the current label
Causality screen of the 40 strongest signals
What the badges mean
- 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.
- 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 flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 1,029 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Anti-interferon antibody positive | 21 | 292.1 180.4–472.8ROR 292.4 · χ² 4,572 / p <1e-300 | 190.6 EB05 131.5 · IC025 +4.5 3/3 methods agree | Lab value / disease marker | serious n=6 · 81% consumer | not reported in cached trials |
| Injection site calcification | 14 | 138.1 79.2–240.7ROR 138.2 · χ² 1,570 / p <1e-300 | 105.4 EB05 66.7 · IC025 +3.7 3/3 methods agree | Labeled (related wording) related wording | serious n=9 | not reported in cached trials |
| Injection site ulcer | 83 | 106.2 84.8–133.0ROR 106.6 · χ² 7,781 / p <1e-300 | 94.7 EB05 78.8 · IC025 +5.6 3/3 methods agree | Labeled (related wording) related wording | serious n=57 | NCT00185211: 1/292 (0.3%) on Interferon Beta-1B (serious AE) |
| Injection site necrosis | 134 | 77.0 64.7–91.7ROR 77.6 · χ² 9,319 / p <1e-300 | 71.3 EB05 61.7 · IC025 +5.5 3/3 methods agree | Labeled adverse reaction exact term | serious n=125 | NCT00185211: 2/292 (0.7%) on Interferon Beta-1B (serious AE) |
| Injection site cellulitis | 108 | 68.6 56.5–83.3ROR 69.0 · χ² 6,703 / p <1e-300 | 63.9 EB05 54.4 · IC025 +5.3 3/3 methods agree | Labeled (related wording) related wording | serious n=102 | NCT00459667: 1/645 (0.2%) on Interferon Beta-1B (serious AE) |
| Injection site scar | 145 | 59.7 50.5–70.5ROR 60.1 · χ² 7,874 / p <1e-300 | 56.2 EB05 48.9 · IC025 +5.3 3/3 methods agree | Labeled (related wording) related wording | serious n=50 | not reported in cached trials |
| Neutralising antibodies positive | 20 | 56.5 36.0–88.5ROR 56.6 · χ² 984 / p 2e-216 | 51.3 EB05 35.1 · IC025 +3.8 3/3 methods agree | Lab value / disease marker | serious n=11 | not reported in cached trials |
| Injection site infection | 147 | 51.7 43.9–61.0ROR 52.1 · χ² 6,934 / p <1e-300 | 49.1 EB05 42.8 · IC025 +5.1 3/3 methods agree | Labeled (related wording) related wording | serious n=131 | NCT00459667: 6/586 (1.0%) on Interferon Beta-1B |
| Injection site atrophy | 66 | 45.8 35.8–58.6ROR 46.0 · χ² 2,733 / p <1e-300 | 43.5 EB05 35.4 · IC025 +4.6 3/3 methods agree | Labeled adverse reaction exact term | serious n=44 | NCT00459667: 1/645 (0.2%) on Interferon Beta-1B |
| Injection site erosion | 14 | 45.7 26.8–78.1ROR 45.8 · χ² 546 / p 5e-121 | 41.6 EB05 26.4 · IC025 +3.2 3/3 methods agree | Labeled (related wording) related wording | serious n=8 | not reported in cached trials |
| Needle fatigue | 18 | 45.0 28.1–72.1ROR 45.0 · χ² 702 / p 6e-155 | 41.5 EB05 27.8 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | – | not reported in cached trials |
| Progressive multiple sclerosis | 41 | 39.9 29.2–54.5ROR 40.0 · χ² 1,462 / p <1e-300 | 37.9 EB05 29.1 · IC025 +4.2 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious n=39 | not reported in cached trials |
| Injection site abscess | 79 | 36.1 28.9–45.2ROR 36.3 · χ² 2,579 / p <1e-300 | 34.7 EB05 28.8 · IC025 +4.5 3/3 methods agree | Labeled adverse reaction exact term | serious n=72 | not reported in cached trials |
| Injection site scab | 28 | 33.1 22.7–48.1ROR 33.1 · χ² 814 / p 3e-179 | 31.5 EB05 22.9 · IC025 +3.7 3/3 methods agree | Labeled (related wording) related wording | serious n=13 | not reported in cached trials |
| Hemianaesthesia | 20 | 27.9 17.9–43.5ROR 28.0 · χ² 480 / p 1e-106 | 26.6 EB05 18.2 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=18 | not reported in cached trials |
| Relapsing-remitting multiple sclerosis | 21 | 27.4 17.8–42.3ROR 27.4 · χ² 496 / p 4e-110 | 26.2 EB05 18.1 · IC025 +3.3 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious n=20 | not reported in cached trials |
| Multiple sclerosis | 1,169 | 27.4 25.9–29.0ROR 29.1 · χ² 29,052 / p <1e-300 | 26.7 EB05 25.5 · IC025 +4.6 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 38.5 | NCT00459667: 1/586 (0.2%) on Interferon Beta-1B (serious AE) |
| Postoperative infection | 11 | 25.7 14.1–46.8ROR 25.7 · χ² 232 / p 1e-52 | 24.1 EB05 14.1 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious n=11 | not reported in cached trials |
| Primary progressive multiple sclerosis | 11 | 25.6 14.1–46.5ROR 25.6 · χ² 230 / p 3e-52 | 23.9 EB05 14.0 · IC025 +2.6 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious n=11 | not reported in cached trials |
| Secondary progressive multiple sclerosis | 39 | 23.1 16.8–31.7ROR 23.1 · χ² 786 / p 3e-173 | 22.4 EB05 17.1 · IC025 +3.6 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious n=36 | not reported in cached trials |
| Multiple sclerosis relapse | 1,345 | 21.8 20.7–23.0ROR 23.4 · χ² 26,256 / p <1e-300 | 21.4 EB05 20.5 · IC025 +4.3 3/3 methods agree | Labeled (related wording) related wording | serious PRR 28.1 | NCT00459667: 45/586 (7.7%) on Interferon Beta-1B |
| Lower extremity mass | 12 | 21.5 12.1–38.0ROR 21.5 · χ² 210 / p 6e-48 | 20.2 EB05 11.9 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious n=6 | not reported in cached trials |
| Lipoatrophy | 17 | 20.1 12.4–32.4ROR 20.1 · χ² 284 / p 5e-64 | 19.2 EB05 12.5 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Influenza like illness (flu-like illness) | 1,403 | 19.0 18.0–20.0ROR 20.4 · χ² 23,573 / p <1e-300 | 18.7 EB05 17.9 · IC025 +4.1 3/3 methods agree | Not in label — unassessed | serious PRR 14.2 | NCT00459667: 72/586 (12.3%) on Interferon Beta-1B |
| Myopathy toxic | 10 | 18.7 10.0–35.0ROR 18.7 · χ² 148 / p 2e-34 | 17.1 EB05 8.9 · IC025 +2.3 3/3 methods agree | Labeled (related wording) related wording | serious n=10 | not reported in cached trials |
| Band sensation | 21 | 18.4 11.9–28.3ROR 18.4 · χ² 322 / p 2e-72 | 17.7 EB05 12.0 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious n=16 | not reported in cached trials |
| Jc virus test positive | 14 | 18.3 10.8–31.1ROR 18.4 · χ² 209 / p 1e-47 | 17.3 EB05 10.4 · IC025 +2.6 3/3 methods agree | Lab value / disease marker | serious n=10 | not reported in cached trials |
| Traumatic fracture | 12 | 18.1 10.2–32.1ROR 18.1 · χ² 175 / p 4e-40 | 16.9 EB05 9.5 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious n=12 | not reported in cached trials |
| Injection site induration | 185 | 15.9 13.8–18.4ROR 16.1 · χ² 2,536 / p <1e-300 | 15.7 EB05 13.9 · IC025 +3.7 3/3 methods agree | Labeled (related wording) related wording | serious n=84 | NCT00459667: 3/586 (0.5%) on Interferon Beta-1B |
| Injection site inflammation | 69 | 15.6 12.3–19.7ROR 15.6 · χ² 913 / p 7e-201 | 15.3 EB05 12.4 · IC025 +3.4 3/3 methods agree | Labeled adverse reaction exact term | serious n=44 | not reported in cached trials |
| Injection site mass | 483 | 14.6 13.4–15.9ROR 14.9 · χ² 6,033 / p <1e-300 | 14.4 EB05 13.4 · IC025 +3.7 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 30.2 | NCT00459667: 4/586 (0.7%) on Interferon Beta-1B |
| Injection site reaction | 841 | 13.6 12.8–14.6ROR 14.2 · χ² 9,749 / p <1e-300 | 13.5 EB05 12.7 · IC025 +3.6 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 26.4 | NCT00459667: 80/586 (13.7%) on Interferon Beta-1B |
| Myelitis transverse | 17 | 13.4 8.3–21.6ROR 13.4 · χ² 181 / p 1e-41 | 12.4 EB05 7.6 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious n=17 | not reported in cached trials |
| Decreased interest | 71 | 13.4 10.6–16.9ROR 13.4 · χ² 791 / p 2e-174 | 13.1 EB05 10.7 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=32 | not reported in cached trials |
| Extensor plantar response | 11 | 13.2 7.3–23.9ROR 13.2 · χ² 111 / p 4e-26 | 11.3 EB05 5.9 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious n=9 | not reported in cached trials |
| Optic neuritis | 108 | 13.2 10.9–15.9ROR 13.2 · χ² 1,189 / p 8e-261 | 12.9 EB05 11.0 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious PRR 14.8 | NCT00459667: 1/586 (0.2%) on Interferon Beta-1B (serious AE) |
| Peroneal nerve palsy | 67 | 13.1 10.3–16.7ROR 13.2 · χ² 729 / p 8e-161 | 12.8 EB05 10.4 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=46 | not reported in cached trials |
| Quadriplegia | 24 | 13.0 8.7–19.4ROR 13.0 · χ² 251 / p 8e-57 | 12.3 EB05 8.3 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious n=24 | not reported in cached trials |
| Joint sprain | 12 | 12.6 7.1–22.2ROR 12.6 · χ² 115 / p 3e-27 | 10.9 EB05 5.9 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious n=12 | NCT00459667: 1/586 (0.2%) on Interferon Beta-1B (serious AE) |
| Injection site dryness | 10 | 12.6 6.7–23.4ROR 12.6 · χ² 94 / p 1e-22 | 10.4 EB05 5.3 · IC025 +1.9 3/3 methods agree | Labeled (related wording) related wording | – | not reported in cached trials |
Trial evidence (ClinicalTrials.gov)
✓ Trial adverse-event data found on ClinicalTrials.gov
Largest completed trials with posted results that list Interferon Beta-1B 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 (13 of 40 signal terms matched).
- NCT00459667 — BEYOND Follow-up: Betaferon®/Betaseron® Efficacy Yielding Outcomes of a New Dose (N=1420, PHASE3; 99 AE terms posted; arms: IFNB-1b 500 mcg; IFNB-1b 250 mcg; IFNB-1b 250 mcg*)
- NCT00185211 — BENEFIT Study (Betaferon® / Betaseron® in Newly Emerging Multiple Sclerosis for Initial Treatment) and BENEFIT (N=468, PHASE3; 118 AE terms posted; arms: Initial IFNB-1b (Interferon Beta-1b); Initial Placebo)
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 |
|---|---|---|---|---|---|---|
| Influenza like illness (flu-like illness) | 1,403 | 19.0 18.0–20.0ROR 20.4 · χ² 23,573 / p <1e-300 | 18.7 EB05 17.9 · IC025 +4.1 3/3 methods agree | Not in label — unassessed | serious PRR 14.2 | NCT00459667: 72/586 (12.3%) on Interferon Beta-1B |
| Multiple sclerosis relapse | 1,345 | 21.8 20.7–23.0ROR 23.4 · χ² 26,256 / p <1e-300 | 21.4 EB05 20.5 · IC025 +4.3 3/3 methods agree | Labeled (related wording) related wording | serious PRR 28.1 | NCT00459667: 45/586 (7.7%) on Interferon Beta-1B |
| Injection site pain (pain where injected) | 1,199 | 4.4 4.1–4.6ROR 4.6 · χ² 3,134 / p <1e-300 | 4.3 EB05 4.1 · IC025 +2.0 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 11.1 | NCT00459667: 1/180 (0.6%) on Interferon Beta-1B (serious AE) |
| Fatigue (tiredness) | 1,196 | 1.7 1.6–1.8ROR 1.7 · χ² 353 / p 5e-79 | 1.7 EB05 1.6 · IC025 +0.7 | Labeled adverse reaction exact term | serious PRR 1.8 | NCT00459667: 89/586 (15.2%) on Interferon Beta-1B |
| Multiple sclerosis | 1,169 | 27.4 25.9–29.0ROR 29.1 · χ² 29,052 / p <1e-300 | 26.7 EB05 25.5 · IC025 +4.6 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 38.5 | NCT00459667: 1/586 (0.2%) on Interferon Beta-1B (serious AE) |
| Injection site erythema (redness where injected) | 977 | 8.8 8.2–9.3ROR 9.2 · χ² 6,704 / p <1e-300 | 8.7 EB05 8.2 · IC025 +3.0 3/3 methods agree | Labeled (related wording) related wording | serious PRR 21.9 | NCT00459667: 70/586 (11.9%) on Interferon Beta-1B |
| Drug ineffective (drug did not work) | 968 | 0.8 0.8–0.9ROR 0.8 · χ² 46 / p 5e-12 | 0.8 EB05 0.8 · IC025 -0.4 PRR-only: not supported by EBGM or IC | Reporting / coding artifact | serious PRR 0.7 | not reported in cached trials |
| Pain | 854 | 1.5 1.4–1.6ROR 1.6 · χ² 160 / p 6e-37 | 1.5 EB05 1.4 · IC025 +0.5 | Labeled adverse reaction exact term | serious PRR 1.6 | NCT00459667: 1/180 (0.6%) on Interferon Beta-1B (serious AE) |
| Headache | 844 | 1.5 1.4–1.6ROR 1.5 · χ² 137 / p 8e-32 | 1.5 EB05 1.4 · IC025 +0.5 | Labeled adverse reaction exact term | serious PRR 1.8 | NCT00459667: 72/586 (12.3%) on Interferon Beta-1B |
| Injection site reaction | 841 | 13.6 12.8–14.6ROR 14.2 · χ² 9,749 / p <1e-300 | 13.5 EB05 12.7 · IC025 +3.6 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 26.4 | NCT00459667: 80/586 (13.7%) on Interferon Beta-1B |
| Fall | 818 | 2.7 2.5–2.9ROR 2.8 · χ² 894 / p 1e-196 | 2.7 EB05 2.6 · IC025 +1.3 3/3 methods agree | Not in label — unassessed | serious PRR 2.6 | not reported in cached trials |
| Depression | 814 | 3.9 3.7–4.2ROR 4.1 · χ² 1,788 / p <1e-300 | 3.9 EB05 3.7 · IC025 +1.9 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 3.0 | NCT00459667: 1/645 (0.2%) on Interferon Beta-1B (serious AE) |
| Gait disturbance | 779 | 4.5 4.2–4.8ROR 4.6 · χ² 2,113 / p <1e-300 | 4.5 EB05 4.2 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 4.6 | not reported in cached trials |
| Pyrexia (fever) | 747 | 2.4 2.2–2.6ROR 2.4 · χ² 603 / p 2e-133 | 2.4 EB05 2.2 · IC025 +1.1 3/3 methods agree | Labeled (related wording) related wording | serious PRR 2.2 | NCT00459667: 6/586 (1.0%) on Interferon Beta-1B |
| Death | 727 | 0.9 0.9–1.0ROR 0.9 · χ² 4 / p 0.022 | 0.9 EB05 0.9 · IC025 -0.2 PRR-only: not supported by EBGM or IC | Outcome field, not a reaction | serious PRR 1.0 | NCT00459667: 1/180 (0.6%) on Interferon Beta-1B (serious AE) |
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.
- Hemianaesthesia — n=20, PRR 27.9
- Influenza like illness — n=1,403, PRR 19.0 (also seen in trial arm)
- Band sensation — n=21, PRR 18.4
- Decreased interest — n=71, PRR 13.4
- Optic neuritis — n=108, PRR 13.2 (also seen in trial arm)
- Peroneal nerve palsy — n=67, PRR 13.1
- Quadriplegia — n=24, PRR 13.0
✓ A hand-written Bradford Hill causality assessment exists for this drug: Interferon beta-1a ↔ Influenza-like illness.
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 Interferon Beta-1B?
In FDA FAERS, the most frequently co-reported reaction terms for Interferon Beta-1B are influenza like illness, multiple sclerosis relapse, injection site pain, fatigue, multiple sclerosis, injection site erythema. 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 Interferon Beta-1B have an FDA boxed warning?
No. The FDA label retrieved for Interferon Beta-1B has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Interferon Beta-1B 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 66311f74-0472-4fa3-848a-06002ca0def5, effective 20260303; matched on
openfda.generic_name.exact:"INTERFERON BETA-1B") - 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, 1,069 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
INTERFERON BETA-1B, results-bearing studies sorted by enrollment)
Page generated 2026-10-08. 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.