Fosaprepitant side effects: what 1,697 FDA adverse event reports show

Fosaprepitant · 165 reaction terms · 14,742 drug–reaction co-reports · data 2026-09-14

Drug class

Substance p/neurokinin-1 (nk 1 ) receptor antagonist

FDA label, Indications wording

Who reports

1,697 reports · 88% serious · 370 with death outcome · 65% female

openFDA FAERS counts, all years, deduplication not applied

Used for

Fosaprepitant for injection, in combination with other antiemetic agents, is indicated in adults and pediatric patients 6 months of age and older for the prevention of: acute and delayed nausea and vomiting associated with initial and repeat courses of highly emetogenic cancer chemotherapy (HEC) including high-dose cisplatin.

FDA label, Indications and Usage

What it is

Fosaprepitant for injection is a sterile, lyophilized formulation containing fosaprepitant dimeglumine, a prodrug of aprepitant, a substance P/neurokinin-1 (NK 1 ) receptor antagonist, an anti.

FDA label, Description section

Boxed warning

None in the current 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 (related wording) 1Reporting / coding artifact 2Lab value / disease marker 1Not in label — unassessed 36

What the badges mean

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. 125 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
Helicobacter infection	210	259.7 228.5–295.3ROR 296.3 · χ² 52,769 / p <1e-300	248.6 EB05 221.6 · IC025 +7.1 3/3 methods agree	Not in label — unassessed	serious PRR 175.9 · ♀ 100% (drug 65%) · 98% clinician	no trial data cached
Folliculitis	207	252.5 221.9–287.4ROR 287.5 · χ² 50,589 / p <1e-300	241.9 EB05 215.5 · IC025 +7.0 3/3 methods agree	Not in label — unassessed	serious PRR 190.3 · ♀ 100% (drug 65%) · 98% clinician	no trial data cached
Hand deformity	199	190.7 167.2–217.6ROR 215.9 · χ² 36,816 / p <1e-300	184.5 EB05 164.0 · IC025 +6.8 3/3 methods agree	Not in label — unassessed	serious PRR 133.6 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Pemphigus	183	184.5 160.7–211.8ROR 206.7 · χ² 32,738 / p <1e-300	178.4 EB05 157.7 · IC025 +6.7 3/3 methods agree	Not in label — unassessed	serious PRR 119.3 · ♀ 100% (drug 65%) · 98% clinician	no trial data cached
Autoimmune disorder	109	142.2 118.5–170.8ROR 151.9 · χ² 14,978 / p <1e-300	137.3 EB05 117.0 · IC025 +6.1 3/3 methods agree	Not in label — unassessed	serious PRR 98.4 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Pericarditis	184	137.9 120.2–158.2ROR 154.5 · χ² 24,606 / p <1e-300	134.5 EB05 118.9 · IC025 +6.4 3/3 methods agree	Not in label — unassessed	serious PRR 89.9 · ♀ 100% (drug 65%) · 98% clinician	no trial data cached
Synovitis	177	122.3 106.3–140.7ROR 136.4 · χ² 20,982 / p <1e-300	119.6 EB05 105.5 · IC025 +6.3 3/3 methods agree	Not in label — unassessed	serious PRR 83.0 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Glossodynia (burning tongue/mouth pain)	211	117.7 103.6–133.6ROR 134.2 · χ² 24,082 / p <1e-300	115.3 EB05 102.9 · IC025 +6.3 3/3 methods agree	Not in label — unassessed	serious PRR 110.4 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Irritable bowel syndrome	177	103.1 89.7–118.7ROR 115.0 · χ² 17,672 / p <1e-300	101.2 EB05 89.3 · IC025 +6.1 3/3 methods agree	Not in label — unassessed	serious PRR 85.0 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Hypercholesterolaemia	75	97.6 78.1–121.8ROR 102.0 · χ² 7,018 / p <1e-300	94.5 EB05 77.9 · IC025 +5.5 3/3 methods agree	Not in label — unassessed	serious PRR 67.3 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Bursitis	93	95.9 78.7–117.0ROR 101.4 · χ² 8,578 / p <1e-300	93.4 EB05 78.5 · IC025 +5.6 3/3 methods agree	Not in label — unassessed	serious PRR 73.3 · ♀ 100% (drug 65%) · 96% clinician	no trial data cached
Wound infection	73	83.5 66.7–104.6ROR 87.2 · χ² 5,831 / p <1e-300	81.2 EB05 66.8 · IC025 +5.3 3/3 methods agree	Not in label — unassessed	serious PRR 58.2 · ♀ 100% (drug 65%) · 95% clinician	no trial data cached
Laryngitis	71	81.3 64.7–102.1ROR 84.8 · χ² 5,516 / p <1e-300	79.1 EB05 64.8 · IC025 +5.3 3/3 methods agree	Not in label — unassessed	serious n=71 · ♀ 100% (drug 65%) · 100% clinician	no trial data cached
Wound	179	80.0 69.6–92.0ROR 89.3 · χ² 13,816 / p <1e-300	78.9 EB05 69.6 · IC025 +5.8 3/3 methods agree	Not in label — unassessed	serious PRR 62.0 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Foot deformity	71	79.5 63.3–99.9ROR 82.9 · χ² 5,393 / p <1e-300	77.4 EB05 63.4 · IC025 +5.3 3/3 methods agree	Not in label — unassessed	serious PRR 60.1 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Impaired healing	199	75.3 66.0–85.8ROR 85.2 · χ² 14,447 / p <1e-300	74.3 EB05 66.0 · IC025 +5.7 3/3 methods agree	Reporting / coding artifact	serious PRR 59.2 · ♀ 100% (drug 65%) · 98% clinician	no trial data cached
Systemic lupus erythematosus	185	64.9 56.6–74.4ROR 72.7 · χ² 11,536 / p <1e-300	64.2 EB05 56.8 · IC025 +5.5 3/3 methods agree	Not in label — unassessed	serious PRR 43.4 · ♀ 100% (drug 65%) · 98% clinician	no trial data cached
Joint range of motion decreased	68	63.1 50.0–79.7ROR 65.7 · χ² 4,078 / p <1e-300	61.8 EB05 50.4 · IC025 +5.0 3/3 methods agree	Not in label — unassessed	serious PRR 52.4 · ♀ 100% (drug 65%) · 97% clinician	no trial data cached
Sciatica	70	54.7 43.5–68.9ROR 57.0 · χ² 3,626 / p <1e-300	53.7 EB05 44.0 · IC025 +4.9 3/3 methods agree	Not in label — unassessed	serious PRR 47.9 · ♀ 100% (drug 65%) · 96% clinician	no trial data cached
Contraindicated product administered	130	53.4 45.3–63.1ROR 57.8 · χ² 6,619 / p <1e-300	52.8 EB05 45.6 · IC025 +5.2 3/3 methods agree	Reporting / coding artifact	serious PRR 43.4 · ♀ 100% (drug 65%) · 98% clinician	no trial data cached
Hepatic cirrhosis	79	52.4 42.2–65.0ROR 54.9 · χ² 3,920 / p <1e-300	51.6 EB05 42.7 · IC025 +4.9 3/3 methods agree	Not in label — unassessed	serious PRR 34.6 · ♀ 97% (drug 65%) · 94% clinician	no trial data cached
Infusion related reaction (reaction during infusion)	277	52.0 46.7–57.9ROR 61.9 · χ² 13,790 / p <1e-300	51.6 EB05 46.7 · IC025 +5.4 3/3 methods agree	Not in label — unassessed	serious PRR 40.1 · ♀ 91% (drug 65%) · 97% clinician	no trial data cached
Lower respiratory tract infection	185	50.6 44.2–58.0ROR 56.7 · χ² 8,930 / p <1e-300	50.2 EB05 44.4 · IC025 +5.2 3/3 methods agree	Not in label — unassessed	serious PRR 34.9 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Arthropathy	205	45.5 40.0–51.8ROR 51.7 · χ² 8,878 / p <1e-300	45.2 EB05 40.2 · IC025 +5.1 3/3 methods agree	Not in label — unassessed	serious PRR 36.2 · ♀ 100% (drug 65%) · 100% clinician	no trial data cached
Obesity	58	45.0 35.0–58.0ROR 46.6 · χ² 2,447 / p <1e-300	44.3 EB05 35.5 · IC025 +4.6 3/3 methods agree	Not in label — unassessed	serious PRR 34.1 · ♀ 100% (drug 65%) · 100% clinician	no trial data cached
Fibromyalgia	88	44.9 36.6–55.1ROR 47.3 · χ² 3,724 / p <1e-300	44.3 EB05 37.1 · IC025 +4.8 3/3 methods agree	Not in label — unassessed	serious PRR 38.5 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Sleep disorder due to a general medical condition	58	44.4 34.5–57.3ROR 46.0 · χ² 2,413 / p <1e-300	43.7 EB05 35.0 · IC025 +4.6 3/3 methods agree	Not in label — unassessed	serious PRR 57.4 · ♀ 100% (drug 65%) · 93% clinician	no trial data cached
Blister	200	44.2 38.8–50.4ROR 50.0 · χ² 8,401 / p <1e-300	43.9 EB05 39.0 · IC025 +5.1 3/3 methods agree	Not in label — unassessed	serious PRR 47.7 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Lower limb fracture	68	44.1 34.9–55.7ROR 45.9 · χ² 2,816 / p <1e-300	43.5 EB05 35.5 · IC025 +4.7 3/3 methods agree	Not in label — unassessed	serious PRR 31.6 · ♀ 100% (drug 65%) · 94% clinician	no trial data cached
Weight fluctuation	37	44.0 32.0–60.6ROR 45.0 · χ² 1,508 / p <1e-300	43.0 EB05 32.5 · IC025 +4.3 3/3 methods agree	Not in label — unassessed	serious n=37 · ♀ 100% (drug 65%) · 100% clinician	no trial data cached
Pulmonary fibrosis	66	42.8 33.8–54.2ROR 44.5 · χ² 2,645 / p <1e-300	42.2 EB05 34.3 · IC025 +4.6 3/3 methods agree	Not in label — unassessed	serious PRR 28.2 · ♀ 100% (drug 65%) · 95% clinician	no trial data cached
Discomfort	208	42.5 37.4–48.3ROR 48.3 · χ² 8,386 / p <1e-300	42.2 EB05 37.6 · IC025 +5.0 3/3 methods agree	Not in label — unassessed	serious PRR 48.4 · ♀ 98% (drug 65%) · 98% clinician	no trial data cached
Ill-defined disorder	201	41.0 36.0–46.7ROR 46.3 · χ² 7,793 / p <1e-300	40.7 EB05 36.2 · IC025 +5.0 3/3 methods agree	Not in label — unassessed	serious PRR 40.3 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Stomatitis (mouth sores)	199	40.6 35.7–46.3ROR 45.9 · χ² 7,651 / p <1e-300	40.4 EB05 35.9 · IC025 +5.0 3/3 methods agree	Not in label — unassessed	serious PRR 39.8 · ♀ 95% (drug 65%) · 98% clinician	no trial data cached
Liver injury	77	39.4 31.7–49.1ROR 41.3 · χ² 2,841 / p <1e-300	39.0 EB05 32.2 · IC025 +4.6 3/3 methods agree	Not in label — unassessed	serious PRR 26.7 · ♀ 95% (drug 65%) · 92% clinician	no trial data cached
Hepatic enzyme increased	204	37.2 32.7–42.3ROR 42.1 · χ² 7,147 / p <1e-300	37.0 EB05 32.9 · IC025 +4.9 3/3 methods agree	Lab value / disease marker	serious PRR 35.1 · ♀ 99% (drug 65%) · 100% clinician	no trial data cached
Prescribed overdose	55	35.2 27.1–45.7ROR 36.3 · χ² 1,790 / p <1e-300	34.7 EB05 27.7 · IC025 +4.3 3/3 methods agree	Not in label — unassessed	serious PRR 39.2 · ♀ 96% (drug 65%) · 93% clinician	no trial data cached
Ear infection	74	34.5 27.6–43.2ROR 36.0 · χ² 2,372 / p <1e-300	34.2 EB05 28.1 · IC025 +4.4 3/3 methods agree	Labeled (related wording) related wording	serious PRR 41.1 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Frequent bowel movements	74	34.1 27.2–42.6ROR 35.6 · χ² 2,338 / p <1e-300	33.7 EB05 27.7 · IC025 +4.4 3/3 methods agree	Not in label — unassessed	serious PRR 34.3 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Delirium	94	33.7 27.6–41.0ROR 35.6 · χ² 2,943 / p <1e-300	33.4 EB05 28.1 · IC025 +4.5 3/3 methods agree	Not in label — unassessed	serious PRR 22.4 · ♀ 95% (drug 65%) · 95% clinician	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
Dyspnoea (shortness of breath)	321	7.0 6.4–7.7ROR 8.4 · χ² 1,693 / p <1e-300	6.9 EB05 6.3 · IC025 +2.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 5.6 · ♀ 86% (drug 65%) · 97% clinician	no trial data cached
Infusion related reaction (reaction during infusion)	277	52.0 46.7–57.9ROR 61.9 · χ² 13,790 / p <1e-300	51.6 EB05 46.7 · IC025 +5.4 3/3 methods agree	Not in label — unassessed	serious PRR 40.1 · ♀ 91% (drug 65%) · 97% clinician	no trial data cached
Alopecia (hair loss)	250	15.7 14.0–17.6ROR 18.2 · χ² 3,456 / p <1e-300	15.7 EB05 14.1 · IC025 +3.7 3/3 methods agree	Not in label — unassessed	serious PRR 20.6 · ♀ 100% (drug 65%) · 90% clinician	no trial data cached
Hypersensitivity (allergic reaction)	232	15.5 13.7–17.4ROR 17.8 · χ² 3,151 / p <1e-300	15.4 EB05 13.8 · IC025 +3.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 18.3 · ♀ 94% (drug 65%) · 99% clinician	no trial data cached
Arthralgia (joint pain)	224	6.7 5.9–7.5ROR 7.5 · χ² 1,097 / p 7e-241	6.6 EB05 5.9 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 7.9 · ♀ 97% (drug 65%) · 98% clinician	no trial data cached
Pyrexia (fever)	223	8.0 7.0–9.0ROR 9.0 · χ² 1,372 / p 2e-300	7.9 EB05 7.0 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious PRR 6.5 · ♀ 89% (drug 65%) · 96% clinician	no trial data cached
Confusional state (confusion)	219	16.7 14.8–18.9ROR 19.1 · χ² 3,243 / p <1e-300	16.7 EB05 14.9 · IC025 +3.8 3/3 methods agree	Not in label — unassessed	serious PRR 13.9 · ♀ 98% (drug 65%) · 98% clinician	no trial data cached
Glossodynia (burning tongue/mouth pain)	211	117.7 103.6–133.6ROR 134.2 · χ² 24,082 / p <1e-300	115.3 EB05 102.9 · IC025 +6.3 3/3 methods agree	Not in label — unassessed	serious PRR 110.4 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Helicobacter infection	210	259.7 228.5–295.3ROR 296.3 · χ² 52,769 / p <1e-300	248.6 EB05 221.6 · IC025 +7.1 3/3 methods agree	Not in label — unassessed	serious PRR 175.9 · ♀ 100% (drug 65%) · 98% clinician	no trial data cached
Discomfort	208	42.5 37.4–48.3ROR 48.3 · χ² 8,386 / p <1e-300	42.2 EB05 37.6 · IC025 +5.0 3/3 methods agree	Not in label — unassessed	serious PRR 48.4 · ♀ 98% (drug 65%) · 98% clinician	no trial data cached
Abdominal discomfort	207	15.3 13.5–17.4ROR 17.3 · χ² 2,773 / p <1e-300	15.3 EB05 13.6 · IC025 +3.7 3/3 methods agree	Not in label — unassessed	serious PRR 22.4 · ♀ 99% (drug 65%) · 99% clinician	no trial data cached
Contusion	207	26.6 23.4–30.3ROR 30.2 · χ² 5,096 / p <1e-300	26.5 EB05 23.6 · IC025 +4.4 3/3 methods agree	Not in label — unassessed	serious PRR 30.2 · ♀ 100% (drug 65%) · 99% clinician	no trial data cached
Folliculitis	207	252.5 221.9–287.4ROR 287.5 · χ² 50,589 / p <1e-300	241.9 EB05 215.5 · IC025 +7.0 3/3 methods agree	Not in label — unassessed	serious PRR 190.3 · ♀ 100% (drug 65%) · 98% clinician	no trial data cached
Pruritus (itching)	205	6.7 5.9–7.6ROR 7.5 · χ² 1,006 / p 4e-221	6.6 EB05 5.9 · IC025 +2.5 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 10.0 · ♀ 97% (drug 65%) · 98% clinician	no trial data cached
Gastrointestinal disorder	205	28.7 25.2–32.6ROR 32.5 · χ² 5,464 / p <1e-300	28.6 EB05 25.4 · IC025 +4.5 3/3 methods agree	Not in label — unassessed	serious PRR 28.5 · ♀ 99% (drug 65%) · 98% clinician	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.

Helicobacter infection — n=210, PRR 259.7
Folliculitis — n=207, PRR 252.5
Hand deformity — n=199, PRR 190.7
Pemphigus — n=183, PRR 184.5
Autoimmune disorder — n=109, PRR 142.2
Pericarditis — n=184, PRR 137.9
Synovitis — n=177, PRR 122.3
Glossodynia — n=211, PRR 117.7
Irritable bowel syndrome — n=177, PRR 103.1
Hypercholesterolaemia — n=75, PRR 97.6

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 Fosaprepitant?

In FDA FAERS, the most frequently co-reported reaction terms for Fosaprepitant are dyspnoea, infusion related reaction, alopecia, hypersensitivity, arthralgia, pyrexia. 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 Fosaprepitant have an FDA boxed warning?

No. The FDA label retrieved for Fosaprepitant has no boxed warning; see the label's Warnings and Precautions for the recognised risks.

Do FAERS signals prove that Fosaprepitant 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 21b08b87-70e3-4233-9531-dd6d84eab5d0, effective 20251009; matched on openfda.generic_name.exact:"FOSAPREPITANT")
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, 165 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.