Gefitinib side effects: what 8,974 FDA adverse event reports show

Gefitinib · 1,008 reaction terms · 27,569 drug–reaction co-reports · data 2026-09-14

Drug class

Kinase Inhibitor

FDA label (Established Pharmacologic Class) · compare the class

Who reports

8,974 reports · 95% serious · 1,952 with death outcome · 60% female

openFDA FAERS counts, all years, deduplication not applied

Used for

Gefitinib tablets are indicated for the first-line treatment of patients with metastatic non-small cell lung cancer (NSCLC) whose tumors have epidermal growth factor receptor (EGFR) exon 19 deletions or exon 21 (L858R) substitution mutations as detected by an FDA-approved test [ see Clinical Studies (14) ].

FDA label, Indications and Usage

What it is

Gefitinib is a kinase inhibitor.

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 adverse reaction 5Labeled (related wording) 3Likely indication confounding 7Reporting / coding artifact 2Lab value / disease marker 1Not in label — unassessed 22

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.
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. 968 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
Egfr gene mutation	130	1,233.0 997.5–1,524.2ROR 1,251.2 · χ² 103,460 / p <1e-300	718.1 EB05 620.3 · IC025 +7.3 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious n=130 · 95% clinician	no trial data cached
Acquired gene mutation	258	569.0 497.3–651.1ROR 585.9 · χ² 116,882 / p <1e-300	441.6 EB05 398.1 · IC025 +7.7 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious n=258 · 91% clinician	no trial data cached
Malignant transformation	70	432.5 335.4–557.9ROR 435.9 · χ² 25,014 / p <1e-300	331.3 EB05 271.1 · IC025 +6.3 3/3 methods agree	Not in label — unassessed	serious n=70 · 98% clinician	no trial data cached
Non-small cell lung cancer recurrent	18	162.1 100.5–261.2ROR 162.4 · χ² 2,544 / p <1e-300	130.8 EB05 87.5 · IC025 +4.1 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious n=17	no trial data cached
Metastases to meninges	118	129.8 108.0–156.1ROR 131.5 · χ² 14,159 / p <1e-300	120.6 EB05 103.4 · IC025 +6.0 3/3 methods agree	Not in label — unassessed	serious n=118	no trial data cached
Drug resistance	1,251	119.7 113.5–126.2ROR 138.9 · χ² 139,993 / p <1e-300	113.6 EB05 108.4 · IC025 +6.7 3/3 methods agree	Reporting / coding artifact	serious PRR 77.0	no trial data cached
Lymphangiosis carcinomatosa	43	100.5 74.1–136.3ROR 101.0 · χ² 3,965 / p <1e-300	92.5 EB05 71.5 · IC025 +5.0 3/3 methods agree	Not in label — unassessed	serious n=41 · ♀ 39% (drug 60%) · 100% clinician	no trial data cached
Lung adenocarcinoma stage iv	14	89.4 52.4–152.4ROR 89.5 · χ² 1,094 / p 3e-240	77.3 EB05 49.0 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious n=14	no trial data cached
Metastases to pleura	34	78.8 56.0–110.9ROR 79.1 · χ² 2,452 / p <1e-300	73.2 EB05 54.8 · IC025 +4.6 3/3 methods agree	Not in label — unassessed	serious n=34 · ♀ 37% (drug 60%)	no trial data cached
Metastases to central nervous system	377	70.8 64.1–78.3ROR 73.9 · χ² 25,134 / p <1e-300	68.5 EB05 62.9 · IC025 +5.8 3/3 methods agree	Not in label — unassessed	serious PRR 41.8	no trial data cached
Lung carcinoma cell type unspecified recurrent	18	70.4 44.1–112.5ROR 70.6 · χ² 1,129 / p 8e-248	64.0 EB05 42.8 · IC025 +3.8 3/3 methods agree	Not in label — unassessed	serious n=18	no trial data cached
Paronychia	126	70.1 58.8–83.5ROR 71.0 · χ² 8,259 / p <1e-300	67.4 EB05 58.1 · IC025 +5.5 3/3 methods agree	Labeled adverse reaction exact term	serious n=118	no trial data cached
Metastases to adrenals	24	62.6 41.8–93.9ROR 62.8 · χ² 1,358 / p 1e-297	58.3 EB05 41.3 · IC025 +4.1 3/3 methods agree	Not in label — unassessed	serious n=23	no trial data cached
Gene mutation	45	54.1 40.3–72.7ROR 54.4 · χ² 2,242 / p <1e-300	51.8 EB05 40.3 · IC025 +4.6 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious n=44	no trial data cached
Small cell lung cancer	31	50.6 35.5–72.2ROR 50.8 · χ² 1,428 / p <1e-300	48.2 EB05 35.6 · IC025 +4.2 3/3 methods agree	Likely indication confounding term in indications	serious n=31 · 93% clinician	no trial data cached
Malignant neoplasm progression	1,821	42.5 40.8–44.3ROR 53.1 · χ² 72,811 / p <1e-300	41.8 EB05 40.2 · IC025 +5.3 3/3 methods agree	Reporting / coding artifact	serious PRR 25.8	no trial data cached
Malignant pleural effusion	30	42.4 29.6–60.8ROR 42.5 · χ² 1,150 / p 2e-252	40.7 EB05 29.9 · IC025 +4.0 3/3 methods agree	Not in label — unassessed	serious n=29	no trial data cached
Carcinoembryonic antigen increased	32	39.4 27.8–55.8ROR 39.5 · χ² 1,139 / p 6e-250	37.9 EB05 28.1 · IC025 +4.0 3/3 methods agree	Lab value / disease marker	serious n=32	no trial data cached
Cutaneous symptom	11	39.1 21.5–70.9ROR 39.1 · χ² 365 / p 1e-81	36.2 EB05 21.6 · IC025 +2.8 3/3 methods agree	Labeled (related wording) related wording	serious n=11	no trial data cached
Hepatobiliary disease	10	37.7 20.2–70.3ROR 37.7 · χ² 316 / p 5e-71	34.8 EB05 20.2 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious n=10	no trial data cached
Dermatitis acneiform	84	32.9 26.5–40.7ROR 33.2 · χ² 2,529 / p <1e-300	32.2 EB05 26.8 · IC025 +4.4 3/3 methods agree	Labeled adverse reaction exact term	serious n=74 · 94% clinician	no trial data cached
Hydrothorax	11	31.2 17.2–56.5ROR 31.2 · χ² 288 / p 7e-65	29.3 EB05 17.4 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious n=10	no trial data cached
Recall phenomenon	10	28.3 15.2–52.7ROR 28.3 · χ² 234 / p 5e-53	26.6 EB05 15.2 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious n=7	no trial data cached
Non-small cell lung cancer metastatic	10	27.5 14.7–51.2ROR 27.5 · χ² 227 / p 2e-51	25.8 EB05 14.7 · IC025 +2.5 3/3 methods agree	Likely indication confounding term in indications	serious n=9	no trial data cached
Metastasis	82	27.0 21.7–33.5ROR 27.2 · χ² 2,004 / p <1e-300	26.6 EB05 22.1 · IC025 +4.2 3/3 methods agree	Not in label — unassessed	serious PRR 16.4	no trial data cached
Metastases to bone	181	26.1 22.6–30.2ROR 26.6 · χ² 4,304 / p <1e-300	25.8 EB05 22.8 · IC025 +4.4 3/3 methods agree	Not in label — unassessed	serious PRR 15.7	no trial data cached
Radiation pneumonitis	22	24.2 15.9–36.8ROR 24.3 · χ² 462 / p 9e-103	23.5 EB05 16.3 · IC025 +3.3 3/3 methods agree	Labeled adverse reaction exact term	serious n=19	no trial data cached
Non-small cell lung cancer	44	21.9 16.3–29.5ROR 22.0 · χ² 850 / p 3e-187	21.6 EB05 16.7 · IC025 +3.6 3/3 methods agree	Likely indication confounding term in indications	serious n=42 · ♀ 32% (drug 60%)	no trial data cached
Oral intake reduced	22	21.1 13.9–32.2ROR 21.2 · χ² 399 / p 5e-89	20.6 EB05 14.2 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious n=21 · 100% clinician	no trial data cached
Metastases to lung	102	20.8 17.2–25.3ROR 21.1 · χ² 1,889 / p <1e-300	20.6 EB05 17.4 · IC025 +3.9 3/3 methods agree	Not in label — unassessed	serious PRR 12.6 · 99% clinician	no trial data cached
Interstitial lung disease	419	20.4 18.6–22.4ROR 21.4 · χ² 7,675 / p <1e-300	20.2 EB05 18.7 · IC025 +4.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 12.0 · 98% clinician	no trial data cached
Po2 decreased	10	20.3 10.9–37.9ROR 20.4 · χ² 164 / p 9e-38	19.0 EB05 10.1 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious n=10	no trial data cached
Cystitis haemorrhagic	34	19.9 14.2–27.9ROR 20.0 · χ² 587 / p 5e-130	19.6 EB05 14.6 · IC025 +3.4 3/3 methods agree	Labeled (related wording) related wording	serious n=29 · 100% clinician	no trial data cached
Xerosis	10	19.2 10.3–35.8ROR 19.3 · χ² 154 / p 1e-35	17.8 EB05 9.3 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious n=10	no trial data cached
Lung adenocarcinoma	24	18.7 12.5–27.9ROR 18.8 · χ² 382 / p 3e-85	18.2 EB05 12.8 · IC025 +3.1 3/3 methods agree	Labeled (related wording) related wording	serious n=22	no trial data cached
Anorexia	100	18.0 14.8–21.9ROR 18.2 · χ² 1,578 / p <1e-300	17.8 EB05 15.1 · IC025 +3.7 3/3 methods agree	Not in label — unassessed	serious PRR 13.0 · 98% clinician	no trial data cached
Skin toxicity	42	17.7 13.1–24.0ROR 17.8 · χ² 641 / p 1e-141	17.4 EB05 13.4 · IC025 +3.4 3/3 methods agree	Labeled adverse reaction exact term	serious n=39 · 95% clinician	no trial data cached
Metastases to lymph nodes	49	17.2 13.0–22.8ROR 17.3 · χ² 726 / p 3e-160	16.9 EB05 13.3 · IC025 +3.4 3/3 methods agree	Not in label — unassessed	serious n=49	no trial data cached
Metastases to spine	24	16.8 11.3–25.2ROR 16.9 · χ² 340 / p 4e-76	16.4 EB05 11.4 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious n=24	no trial data cached
Metastases to liver	118	15.8 13.2–18.9ROR 16.0 · χ² 1,614 / p <1e-300	15.7 EB05 13.4 · IC025 +3.6 3/3 methods agree	Not in label — unassessed	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
Malignant neoplasm progression	1,821	42.5 40.8–44.3ROR 53.1 · χ² 72,811 / p <1e-300	41.8 EB05 40.2 · IC025 +5.3 3/3 methods agree	Reporting / coding artifact	serious PRR 25.8	no trial data cached
Drug resistance	1,251	119.7 113.5–126.2ROR 138.9 · χ² 139,993 / p <1e-300	113.6 EB05 108.4 · IC025 +6.7 3/3 methods agree	Reporting / coding artifact	serious PRR 77.0	no trial data cached
Diarrhoea (diarrhea)	904	3.3 3.1–3.5ROR 3.5 · χ² 1,480 / p <1e-300	3.3 EB05 3.1 · IC025 +1.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 3.3	no trial data cached
Death	757	2.1 1.9–2.2ROR 2.2 · χ² 426 / p 6e-95	2.1 EB05 1.9 · IC025 +0.9	Outcome field, not a reaction	serious PRR 1.2	no trial data cached
Rash	642	3.5 3.2–3.7ROR 3.7 · χ² 1,144 / p 4e-251	3.5 EB05 3.2 · IC025 +1.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 4.3	no trial data cached
Disease progression	461	9.2 8.4–10.0ROR 9.6 · χ² 3,352 / p <1e-300	9.1 EB05 8.4 · IC025 +3.0 3/3 methods agree	Reporting / coding artifact	serious PRR 5.8 · 93% clinician	no trial data cached
Interstitial lung disease	419	20.4 18.6–22.4ROR 21.4 · χ² 7,675 / p <1e-300	20.2 EB05 18.7 · IC025 +4.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 12.0 · 98% clinician	no trial data cached
Nausea	379	1.1 1.0–1.2ROR 1.1 · χ² 5 / p 0.012	1.1 EB05 1.0 · IC025 -0.0 PRR-only: not supported by EBGM or IC	Labeled adverse reaction exact term	serious PRR 1.3	no trial data cached
Metastases to central nervous system	377	70.8 64.1–78.3ROR 73.9 · χ² 25,134 / p <1e-300	68.5 EB05 62.9 · IC025 +5.8 3/3 methods agree	Not in label — unassessed	serious PRR 41.8	no trial data cached
Dyspnoea (shortness of breath)	331	1.4 1.2–1.5ROR 1.4 · χ² 33 / p 4e-9	1.4 EB05 1.2 · IC025 +0.3	Labeled adverse reaction exact term	serious PRR 1.1	no trial data cached
Vomiting	326	1.6 1.5–1.8ROR 1.6 · χ² 80 / p 2e-19	1.6 EB05 1.5 · IC025 +0.5	Labeled adverse reaction exact term	serious PRR 1.4	no trial data cached
Drug ineffective (drug did not work)	297	0.5 0.5–0.6ROR 0.5 · χ² 134 / p 3e-31	0.5 EB05 0.5 · IC025 -1.1 PRR-only: not supported by EBGM or IC	Reporting / coding artifact	serious PRR 0.9	no trial data cached
Pneumonia (lung infection)	273	2.0 1.8–2.2ROR 2.0 · χ² 132 / p 7e-31	2.0 EB05 1.8 · IC025 +0.8	Labeled adverse reaction exact term	serious PRR 1.2	no trial data cached
Pyrexia (fever)	271	1.8 1.6–2.1ROR 1.9 · χ² 103 / p 2e-24	1.8 EB05 1.7 · IC025 +0.7	Labeled adverse reaction exact term	serious PRR 1.4	no trial data cached
Acquired gene mutation	258	569.0 497.3–651.1ROR 585.9 · χ² 116,882 / p <1e-300	441.6 EB05 398.1 · IC025 +7.7 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious n=258 · 91% 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.

Malignant transformation — n=70, PRR 432.5
Metastases to meninges — n=118, PRR 129.8
Lymphangiosis carcinomatosa — n=43, PRR 100.5
Metastases to pleura — n=34, PRR 78.8
Metastases to central nervous system — n=377, PRR 70.8
Metastases to adrenals — n=24, PRR 62.6
Malignant pleural effusion — n=30, PRR 42.4
Metastasis — n=82, PRR 27.0
Metastases to bone — n=181, PRR 26.1
Oral intake reduced — n=22, PRR 21.1

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 Gefitinib?

In FDA FAERS, the most frequently co-reported reaction terms for Gefitinib are diarrhoea, rash, interstitial lung disease, nausea, metastases to central nervous system, dyspnoea. 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 Gefitinib have an FDA boxed warning?

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

Do FAERS signals prove that Gefitinib 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 0afc12dd-12f8-4def-9027-f38412a862b9, effective 20230222; matched on openfda.generic_name.exact:"GEFITINIB")
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, 1,008 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.