Andexanet Alfa side effects: what 708 FDA adverse event reports show

Andexanet Alfa · Andexxa · 13 reaction terms · 250 drug–reaction co-reports · data 2026-09-14

Drug class

Recombinant modified human factor xa (fxa) protein

FDA label, Indications wording

Brand names

Andexxa

openFDA label

Who reports

708 reports · 93% serious · 321 with death outcome · 45% female

openFDA FAERS counts, all years, deduplication not applied

Used for

ANDEXXA is indicated for patients treated with rivaroxaban or apixaban, when reversal of anticoagulation is needed due to life-threatening or uncontrolled bleeding. This indication is approved under accelerated approval based on the change from baseline in anti-FXa activity in healthy volunteers . An improvement in hemostasis has not been established.

FDA label, Indications and Usage

What it is

ANDEXXA (coagulation factor Xa (recombinant), inactivated-zhzo) is a sterile, white to off-white lyophilized powder available in single-dose vials. Each 200 mg vial delivers 200 mg of coagulat.

FDA label, Description section

Boxed warning

THROMBOEMBOLIC RISKS, ISCHEMIC RISKS, CARDIAC ARREST, AND SUDDEN DEATHS Treatment with ANDEXXA has been associated with serious and life-threatening adverse events, including: ( 5.1 ) • Arterial and venous thromboemb.

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 11 strongest signals

Labeled — boxed warning 2Labeled (related wording) 2Not in label — unassessed 7

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 (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
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. 2 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
Cerebral infarction	54	65.5 50.7–84.7ROR 70.9 · χ² 3,364 / p <1e-300	64.0 EB05 50.9 · IC025 +4.9 3/3 methods agree	Not in label — unassessed	serious PRR 40.7 · 98% clinician	no trial data cached
Ischaemic stroke	36	59.8 43.5–82.2ROR 62.9 · χ² 2,020 / p <1e-300	57.9 EB05 43.7 · IC025 +4.5 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 37.1 · ♀ 68% (drug 45%)	no trial data cached
Subdural haematoma	19	39.2 25.2–61.1ROR 40.3 · χ² 670 / p 6e-148	37.8 EB05 25.6 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious PRR 23.2	no trial data cached
Acute myocardial infarction	37	37.1 27.1–50.7ROR 39.0 · χ² 1,262 / p 8e-277	36.4 EB05 27.6 · IC025 +4.1 3/3 methods agree	Labeled (related wording) related wording	serious PRR 23.0 · ♀ 24% (drug 45%) · 92% clinician	no trial data cached
Cerebral haemorrhage	36	29.8 21.7–41.0ROR 31.4 · χ² 976 / p 2e-214	29.4 EB05 22.2 · IC025 +3.9 3/3 methods agree	Not in label — unassessed	serious PRR 18.6 · 100% clinician	no trial data cached
Brain oedema	12	28.2 16.1–49.4ROR 28.6 · χ² 288 / p 8e-65	27.0 EB05 16.4 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious PRR 17.7	no trial data cached
Haemorrhage intracranial	12	23.7 13.5–41.5ROR 24.1 · χ² 239 / p 4e-54	22.8 EB05 13.6 · IC025 +2.7 3/3 methods agree	Labeled (related wording) related wording	serious PRR 13.5	no trial data cached
Subarachnoid haemorrhage	7	20.3 9.7–42.4ROR 20.5 · χ² 110 / p 5e-26	18.0 EB05 7.5 · IC025 +1.8 3/3 methods agree	Not in label — unassessed	serious PRR 12.6	no trial data cached
Ventricular tachycardia	10	17.9 9.7–33.1ROR 18.1 · χ² 143 / p 3e-33	16.5 EB05 8.5 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious PRR 11.2	no trial data cached
Haematoma	13	14.8 8.6–25.4ROR 15.1 · χ² 154 / p 1e-35	13.7 EB05 7.7 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious PRR 9.2	no trial data cached
Disseminated intravascular coagulation	7	14.7 7.0–30.7ROR 14.8 · χ² 76 / p 1e-18	11.8 EB05 4.9 · IC025 +1.6 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 9.2	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
Cerebral infarction	54	65.5 50.7–84.7ROR 70.9 · χ² 3,364 / p <1e-300	64.0 EB05 50.9 · IC025 +4.9 3/3 methods agree	Not in label — unassessed	serious PRR 40.7 · 98% clinician	no trial data cached
Acute myocardial infarction	37	37.1 27.1–50.7ROR 39.0 · χ² 1,262 / p 8e-277	36.4 EB05 27.6 · IC025 +4.1 3/3 methods agree	Labeled (related wording) related wording	serious PRR 23.0 · ♀ 24% (drug 45%) · 92% clinician	no trial data cached
Cerebral haemorrhage	36	29.8 21.7–41.0ROR 31.4 · χ² 976 / p 2e-214	29.4 EB05 22.2 · IC025 +3.9 3/3 methods agree	Not in label — unassessed	serious PRR 18.6 · 100% clinician	no trial data cached
Ischaemic stroke	36	59.8 43.5–82.2ROR 62.9 · χ² 2,020 / p <1e-300	57.9 EB05 43.7 · IC025 +4.5 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 37.1 · ♀ 68% (drug 45%)	no trial data cached
Subdural haematoma	19	39.2 25.2–61.1ROR 40.3 · χ² 670 / p 6e-148	37.8 EB05 25.6 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious PRR 23.2	no trial data cached
Haematoma	13	14.8 8.6–25.4ROR 15.1 · χ² 154 / p 1e-35	13.7 EB05 7.7 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious PRR 9.2	no trial data cached
Haemorrhage intracranial	12	23.7 13.5–41.5ROR 24.1 · χ² 239 / p 4e-54	22.8 EB05 13.6 · IC025 +2.7 3/3 methods agree	Labeled (related wording) related wording	serious PRR 13.5	no trial data cached
Brain oedema	12	28.2 16.1–49.4ROR 28.6 · χ² 288 / p 8e-65	27.0 EB05 16.4 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious PRR 17.7	no trial data cached
Ventricular tachycardia	10	17.9 9.7–33.1ROR 18.1 · χ² 143 / p 3e-33	16.5 EB05 8.5 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious PRR 11.2	no trial data cached
Disseminated intravascular coagulation	7	14.7 7.0–30.7ROR 14.8 · χ² 76 / p 1e-18	11.8 EB05 4.9 · IC025 +1.6 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 9.2	no trial data cached
Subarachnoid haemorrhage	7	20.3 9.7–42.4ROR 20.5 · χ² 110 / p 5e-26	18.0 EB05 7.5 · IC025 +1.8 3/3 methods agree	Not in label — unassessed	serious PRR 12.6	no trial data cached
Status epilepticus	4	10.5 3.9–27.8ROR 10.5 · χ² 25 / p 2e-7	6.1 EB05 2.3 · IC025 +0.6 3/3 methods agree	Not in label — unassessed	serious PRR 6.5	no trial data cached
Rebound effect	3	7.8 2.5–24.2ROR 7.9 · χ² 12 / p 3e-4	4.2 EB05 1.6 · IC025 -0.1 PRR-only: not supported by EBGM or IC	Not in label — unassessed	serious PRR 7.8	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.

Cerebral infarction — n=54, PRR 65.5
Cerebral haemorrhage — n=36, PRR 29.8

✓ 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 Andexanet Alfa?

In FDA FAERS, the most frequently co-reported reaction terms for Andexanet Alfa are cerebral infarction, acute myocardial infarction, cerebral haemorrhage, ischaemic stroke, subdural haematoma, haematoma. 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 Andexanet Alfa have an FDA boxed warning?

Yes. The current FDA label carries a boxed warning: THROMBOEMBOLIC RISKS, ISCHEMIC RISKS, CARDIAC ARREST, AND SUDDEN DEATHS Treatment with ANDEXXA has been associated with serious and life-threatening adverse events, including: ( 5.1 ) • Arterial and venous thromboemb.

Do FAERS signals prove that Andexanet Alfa 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 2d9d90a6-63e6-46ef-96ff-dd6519ae7b6c, effective 20250523; matched on openfda.generic_name.exact:"ANDEXANET ALFA")
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, 13 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.