Ropeginterferon Alfa-2B side effects: what 1,774 FDA adverse event reports show

Ropeginterferon Alfa-2B · Besremi, Besremi Pen · 65 reaction terms · 1,774 drug–reaction co-reports · data 2026-09-14

Drug class

Interferon alfa-2b

FDA label (Established Pharmacologic Class)

Brand names

Besremi, Besremi Pen

openFDA label

Who reports

1,774 reports · 22% serious · 29 with death outcome · 60% female

openFDA FAERS counts, all years, deduplication not applied

Used for

BESREMi is an interferon alfa-2b indicated for: • The treatment of adults with essential thrombocythemia. ( 1.1 ) • The treatment of adults with polycythemia vera. ( 1.2 ) 1.1 Essential Thrombocythemia BESREMi is indicated for the treatment of adults with essential thrombocythemia. 1.2 Polycythemia Vera BESREMi is indicated for the treatment of adults with polycythemia vera.

FDA label, Indications and Usage

What it is

Ropeginterferon alfa-2b-njft, an interferon alfa-2b, is an N-terminal monopegylated covalent conjugate of proline interferon alfa-2b, produced in Escherichia coli cells by recombinant DNA technology, with a methoxy polyethylene glycol (mPEG) moiety.

FDA label, Description section

Boxed warning

RISK OF SERIOUS DISORDERS Risk of Serious Disorders: Interferon alfa products may cause or aggravate fatal or life-threatening neuropsychiatric, autoimmune, ischemic, and infectious disorders. Patients should be monitored closely with periodic clinical and laboratory evaluations.

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 2Labeled adverse reaction 7Labeled (related wording) 4Reporting / coding artifact 10Lab value / disease marker 6Not in label — unassessed 11

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.
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 flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 25 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.

Show: hide coding/lab/outcome terms hide indication terms unlabeled only hide PRR-only

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Platelet count increased	89	81.0 66.1–99.2ROR 85.2 · χ² 6,906 / p <1e-300	79.1 EB05 66.2 · IC025 +5.4 3/3 methods agree	Lab value / disease marker	serious PRR 47.2 · 83% consumer	no trial data cached
Blood iron decreased	25	25.1 17.0–37.0ROR 25.4 · χ² 553 / p 1e-122	24.6 EB05 17.5 · IC025 +3.4 3/3 methods agree	Lab value / disease marker	serious PRR 21.6 · 84% consumer	no trial data cached
Brain fog	29	23.5 16.4–33.7ROR 23.9 · χ² 602 / p 3e-133	23.2 EB05 16.9 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious PRR 20.6 · 83% consumer	no trial data cached
Laboratory test abnormal	52	20.9 16.0–27.3ROR 21.5 · χ² 963 / p 9e-212	20.7 EB05 16.4 · IC025 +3.7 3/3 methods agree	Reporting / coding artifact	serious PRR 17.6 · 90% consumer	no trial data cached
Haematocrit decreased	31	18.4 12.9–26.0ROR 18.7 · χ² 491 / p 4e-109	18.1 EB05 13.3 · IC025 +3.2 3/3 methods agree	Lab value / disease marker	serious PRR 10.6 · 77% consumer	no trial data cached
Influenza like illness (flu-like illness)	109	15.6 13.0–18.7ROR 16.5 · χ² 1,478 / p <1e-300	15.5 EB05 13.2 · IC025 +3.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.4 · 82% consumer	no trial data cached
Blood test abnormal	18	15.2 9.6–24.0ROR 15.3 · χ² 224 / p 6e-51	14.5 EB05 9.2 · IC025 +2.7 3/3 methods agree	Reporting / coding artifact	serious PRR 6.8	no trial data cached
Splenomegaly	15	15.1 9.1–25.1ROR 15.3 · χ² 184 / p 3e-42	14.3 EB05 8.5 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 9.0	no trial data cached
Product availability issue	23	12.1 8.1–18.2ROR 12.3 · χ² 224 / p 7e-51	11.4 EB05 7.6 · IC025 +2.6 3/3 methods agree	Reporting / coding artifact	91% consumer	no trial data cached
Needle issue	28	11.6 8.0–16.7ROR 11.7 · χ² 260 / p 9e-59	11.0 EB05 7.7 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious n=1	no trial data cached
Injection site irritation	12	11.2 6.4–19.7ROR 11.3 · χ² 102 / p 3e-24	9.5 EB05 5.2 · IC025 +2.0 3/3 methods agree	Not in label — unassessed	serious n=2	no trial data cached
Injection site discolouration	11	10.5 5.8–18.9ROR 10.5 · χ² 85 / p 1e-20	8.6 EB05 4.7 · IC025 +1.9 3/3 methods agree	Not in label — unassessed	serious n=1	no trial data cached
Bone pain	51	10.3 7.8–13.5ROR 10.6 · χ² 419 / p 2e-93	9.9 EB05 7.7 · IC025 +2.8 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.6 · 84% consumer	no trial data cached
Hepatic enzyme increased	53	9.2 7.1–12.0ROR 9.5 · χ² 381 / p 4e-85	8.8 EB05 6.9 · IC025 +2.6 3/3 methods agree	Labeled — boxed warning synonym match	serious PRR 6.6 · 83% consumer	no trial data cached
Emotional disorder	24	9.1 6.1–13.6ROR 9.3 · χ² 166 / p 3e-38	8.3 EB05 5.7 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious PRR 7.4 · 79% consumer	no trial data cached
Red blood cell count decreased	22	9.1 6.0–13.8ROR 9.2 · χ² 150 / p 8e-35	8.1 EB05 5.5 · IC025 +2.2 3/3 methods agree	Lab value / disease marker	serious PRR 8.6 · 77% consumer	no trial data cached
Insurance issue	11	8.7 4.9–15.8ROR 8.8 · χ² 68 / p 8e-17	7.0 EB05 4.0 · IC025 +1.7 3/3 methods agree	Not in label — unassessed	serious PRR 4.3	no trial data cached
Blood triglycerides increased	13	8.7 5.0–14.9ROR 8.7 · χ² 81 / p 1e-19	7.1 EB05 4.3 · IC025 +1.8 3/3 methods agree	Labeled — boxed warning synonym match	–	no trial data cached
White blood cell count increased	28	8.6 5.9–12.4ROR 8.7 · χ² 180 / p 2e-41	7.8 EB05 5.6 · IC025 +2.3 3/3 methods agree	Lab value / disease marker	serious PRR 9.8 · 86% consumer	no trial data cached
Drug effect less than expected	10	8.4 4.5–15.5ROR 8.4 · χ² 58 / p 1e-14	6.5 EB05 3.6 · IC025 +1.6 3/3 methods agree	Reporting / coding artifact	serious n=1	no trial data cached
Night sweats	22	8.1 5.3–12.2ROR 8.2 · χ² 129 / p 3e-30	7.2 EB05 4.9 · IC025 +2.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 8.3 · 73% consumer	no trial data cached
Blood potassium increased	11	8.0 4.4–14.4ROR 8.1 · χ² 61 / p 3e-15	6.4 EB05 3.7 · IC025 +1.6 3/3 methods agree	Lab value / disease marker	serious PRR 7.5	no trial data cached
Platelet count decreased	65	7.2 5.7–9.2ROR 7.4 · χ² 343 / p 7e-77	6.9 EB05 5.6 · IC025 +2.4 3/3 methods agree	Labeled (related wording) related wording	serious PRR 3.3 · 80% consumer	no trial data cached
Inappropriate schedule of product administration	106	7.1 5.9–8.5ROR 7.5 · χ² 552 / p 2e-122	6.9 EB05 5.9 · IC025 +2.5 3/3 methods agree	Reporting / coding artifact	serious PRR 8.0 · 73% consumer	no trial data cached
Injection site erythema (redness where injected)	70	6.7 5.3–8.4ROR 6.9 · χ² 335 / p 3e-75	6.4 EB05 5.3 · IC025 +2.3 3/3 methods agree	Labeled (related wording) related wording	serious PRR 10.8 · 86% consumer	no trial data cached
Thirst	10	6.6 3.6–12.3ROR 6.7 · χ² 42 / p 4e-11	5.2 EB05 3.0 · IC025 +1.3 3/3 methods agree	Not in label — unassessed	serious PRR 3.2	no trial data cached
Device malfunction	37	6.5 4.7–8.9ROR 6.6 · χ² 167 / p 1e-38	6.1 EB05 4.6 · IC025 +2.1 3/3 methods agree	Reporting / coding artifact	–	no trial data cached
Dry eye	26	6.3 4.3–9.3ROR 6.4 · χ² 112 / p 2e-26	5.8 EB05 4.1 · IC025 +1.9 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.0 · 77% consumer	no trial data cached
Exposure via skin contact	12	6.3 3.6–11.0ROR 6.3 · χ² 48 / p 2e-12	5.2 EB05 3.1 · IC025 +1.4 3/3 methods agree	Reporting / coding artifact	–	no trial data cached
Injection site rash	16	6.2 3.8–10.1ROR 6.3 · χ² 65 / p 3e-16	5.4 EB05 3.5 · IC025 +1.6 3/3 methods agree	Labeled (related wording) related wording	serious n=3	no trial data cached
White blood cell count decreased	56	6.1 4.7–7.9ROR 6.3 · χ² 235 / p 3e-53	5.8 EB05 4.6 · IC025 +2.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 3.7 · 84% consumer	no trial data cached
Depressed mood	27	6.1 4.2–8.8ROR 6.1 · χ² 109 / p 7e-26	5.5 EB05 4.0 · IC025 +1.8 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 3.6 · 70% consumer	no trial data cached
Anger	17	5.9 3.7–9.5ROR 6.0 · χ² 65 / p 5e-16	5.2 EB05 3.4 · IC025 +1.6 3/3 methods agree	Not in label — unassessed	serious PRR 3.0	no trial data cached
Product dose omission in error	13	5.7 3.3–9.8ROR 5.8 · χ² 46 / p 6e-12	4.8 EB05 3.0 · IC025 +1.3 3/3 methods agree	Reporting / coding artifact	serious PRR 9.2	no trial data cached
Pruritus (itching)	171	5.3 4.6–6.2ROR 5.8 · χ² 610 / p 5e-135	5.3 EB05 4.6 · IC025 +2.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 4.5 · 75% consumer	no trial data cached
Irritability	27	5.3 3.6–7.7ROR 5.4 · χ² 90 / p 1e-21	4.9 EB05 3.5 · IC025 +1.7 3/3 methods agree	Not in label — unassessed	serious PRR 3.7	no trial data cached
Product dose omission issue	113	4.7 3.9–5.6ROR 4.9 · χ² 328 / p 1e-73	4.6 EB05 3.9 · IC025 +1.9 3/3 methods agree	Reporting / coding artifact	serious PRR 4.5 · 76% consumer	no trial data cached
Injection site bruising	31	4.6 3.3–6.6ROR 4.7 · χ² 85 / p 1e-20	4.4 EB05 3.2 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 12.0 · 87% consumer	no trial data cached
Mood altered	10	4.3 2.3–8.1ROR 4.4 · χ² 23 / p 1e-6	3.7 EB05 2.2 · IC025 +0.8 3/3 methods agree	Labeled (related wording) related wording	–	no trial data cached
Intentional dose omission	10	4.3 2.3–8.0ROR 4.3 · χ² 22 / p 1e-6	3.7 EB05 2.2 · IC025 +0.8 3/3 methods agree	Reporting / coding artifact	serious PRR 9.4	no trial data cached

Trial evidence (ClinicalTrials.gov)

Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).

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
Pruritus (itching)	171	5.3 4.6–6.2ROR 5.8 · χ² 610 / p 5e-135	5.3 EB05 4.6 · IC025 +2.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 4.5 · 75% consumer	no trial data cached
Product dose omission issue	113	4.7 3.9–5.6ROR 4.9 · χ² 328 / p 1e-73	4.6 EB05 3.9 · IC025 +1.9 3/3 methods agree	Reporting / coding artifact	serious PRR 4.5 · 76% consumer	no trial data cached
Influenza like illness (flu-like illness)	109	15.6 13.0–18.7ROR 16.5 · χ² 1,478 / p <1e-300	15.5 EB05 13.2 · IC025 +3.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.4 · 82% consumer	no trial data cached
Inappropriate schedule of product administration	106	7.1 5.9–8.5ROR 7.5 · χ² 552 / p 2e-122	6.9 EB05 5.9 · IC025 +2.5 3/3 methods agree	Reporting / coding artifact	serious PRR 8.0 · 73% consumer	no trial data cached
Platelet count increased	89	81.0 66.1–99.2ROR 85.2 · χ² 6,906 / p <1e-300	79.1 EB05 66.2 · IC025 +5.4 3/3 methods agree	Lab value / disease marker	serious PRR 47.2 · 83% consumer	no trial data cached
Incorrect dose administered	70	3.7 2.9–4.6ROR 3.8 · χ² 135 / p 2e-31	3.6 EB05 2.9 · IC025 +1.5 3/3 methods agree	Reporting / coding artifact	serious PRR 14.6	no trial data cached
Injection site erythema (redness where injected)	70	6.7 5.3–8.4ROR 6.9 · χ² 335 / p 3e-75	6.4 EB05 5.3 · IC025 +2.3 3/3 methods agree	Labeled (related wording) related wording	serious PRR 10.8 · 86% consumer	no trial data cached
Platelet count decreased	65	7.2 5.7–9.2ROR 7.4 · χ² 343 / p 7e-77	6.9 EB05 5.6 · IC025 +2.4 3/3 methods agree	Labeled (related wording) related wording	serious PRR 3.3 · 80% consumer	no trial data cached
White blood cell count decreased	56	6.1 4.7–7.9ROR 6.3 · χ² 235 / p 3e-53	5.8 EB05 4.6 · IC025 +2.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 3.7 · 84% consumer	no trial data cached
Hepatic enzyme increased	53	9.2 7.1–12.0ROR 9.5 · χ² 381 / p 4e-85	8.8 EB05 6.9 · IC025 +2.6 3/3 methods agree	Labeled — boxed warning synonym match	serious PRR 6.6 · 83% consumer	no trial data cached
Laboratory test abnormal	52	20.9 16.0–27.3ROR 21.5 · χ² 963 / p 9e-212	20.7 EB05 16.4 · IC025 +3.7 3/3 methods agree	Reporting / coding artifact	serious PRR 17.6 · 90% consumer	no trial data cached
Bone pain	51	10.3 7.8–13.5ROR 10.6 · χ² 419 / p 2e-93	9.9 EB05 7.7 · IC025 +2.8 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.6 · 84% consumer	no trial data cached
Device malfunction	37	6.5 4.7–8.9ROR 6.6 · χ² 167 / p 1e-38	6.1 EB05 4.6 · IC025 +2.1 3/3 methods agree	Reporting / coding artifact	–	no trial data cached
Injection site bruising	31	4.6 3.3–6.6ROR 4.7 · χ² 85 / p 1e-20	4.4 EB05 3.2 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 12.0 · 87% consumer	no trial data cached
Haematocrit decreased	31	18.4 12.9–26.0ROR 18.7 · χ² 491 / p 4e-109	18.1 EB05 13.3 · IC025 +3.2 3/3 methods agree	Lab value / disease marker	serious PRR 10.6 · 77% consumer	no trial data cached

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.

Brain fog — n=29, PRR 23.5
Needle issue — n=28, PRR 11.6
Emotional disorder — n=24, PRR 9.1
Irritability — n=27, PRR 5.3
Injection site bruising — n=31, PRR 4.6

✓ A hand-written Bradford Hill causality assessment exists for this drug: Erythropoiesis-stimulating agents (darbepoetin alfa) ↔ Mortality / cardiovascular risk.

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 Ropeginterferon Alfa-2B?

In FDA FAERS, the most frequently co-reported reaction terms for Ropeginterferon Alfa-2B are pruritus, influenza like illness, platelet count increased, injection site erythema, platelet count decreased, white blood cell count decreased. 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 Ropeginterferon Alfa-2B have an FDA boxed warning?

Yes. The current FDA label carries a boxed warning: RISK OF SERIOUS DISORDERS Risk of Serious Disorders: Interferon alfa products may cause or aggravate fatal or life-threatening neuropsychiatric, autoimmune, ischemic, and infectious disorders. Patients should be monitored closely with periodic clinical and laboratory evaluations.

Do FAERS signals prove that Ropeginterferon Alfa-2B 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 9583405d-53a0-49dc-88eb-5e6384ebabcb, effective 20260825; matched on openfda.generic_name.exact:"ROPEGINTERFERON ALFA-2B")
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, field patient.drug.openfda.generic_name.exact, 65 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

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.