Tamoxifen side effects: what 5,727 FDA adverse event reports show
Drug class
Not stated in label
Label matched
Tamoxifen Citrate (Tamoxifen Citrate)
Who reports
5,727 reports · 77% serious · 478 with death outcome · 96% female
Used for
Metastatic Breast Cancer: Tamoxifen citrate tablets are effective in the treatment of metastatic breast cancer in women and men. In premenopausal women with metastatic breast cancer, tamoxifen citrate tablets are an alternative to oophorectomy or ovarian irradiation.
What it is
DESCRIPTION Tamoxifen citrate tablets, USP a nonsteroidal antiestrogen, are for oral administration. Tamoxifen citrate tablets are available as: 10 mg Tablets:
Boxed warning
- For Women with Ductal Carcinoma in Situ (DCIS) and Women at High Risk for Breast Cancer : Serious and life-threatening events associated with tamoxifen citrate in the risk reduction setting (women at high risk for cancer and women with DCIS) include uterine malignancies, stroke and pulmonary embolism.
Causality screen of the 40 strongest signals
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.
- 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. 402 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 |
|---|---|---|---|---|---|---|
| Breast cancer metastatic | 124 | 42.8 35.9–51.0ROR 43.7 · χ² 4,965 / p <1e-300 | 42.1 EB05 36.2 · IC025 +4.9 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 30.4 | no trial data cached |
| Metastases to bone | 181 | 41.0 35.5–47.3ROR 42.3 · χ² 6,942 / p <1e-300 | 40.3 EB05 35.7 · IC025 +4.9 3/3 methods agree | Labeled (related wording) related wording | serious PRR 29.9 | no trial data cached |
| Metastases to lung | 71 | 22.7 18.0–28.6ROR 22.9 · χ² 1,440 / p <1e-300 | 22.4 EB05 18.4 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious PRR 16.5 | no trial data cached |
| Bone disorder | 96 | 19.2 15.8–23.5ROR 19.5 · χ² 1,633 / p <1e-300 | 19.1 EB05 16.1 · IC025 +3.8 3/3 methods agree | Labeled (related wording) related wording | serious PRR 16.1 | no trial data cached |
| Metastases to liver | 89 | 18.7 15.2–23.0ROR 19.0 · χ² 1,465 / p <1e-300 | 18.5 EB05 15.5 · IC025 +3.7 3/3 methods agree | Labeled (related wording) related wording | serious PRR 13.7 | no trial data cached |
| Tooth extraction | 62 | 18.3 14.3–23.5ROR 18.5 · χ² 993 / p 3e-218 | 18.1 EB05 14.6 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious PRR 18.7 · 95% clinician | no trial data cached |
| Osteonecrosis (bone death) | 136 | 15.1 12.8–17.8ROR 15.4 · χ² 1,769 / p <1e-300 | 15.0 EB05 13.0 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious PRR 11.0 · 100% clinician | no trial data cached |
| Osteonecrosis of jaw (jawbone death) | 96 | 14.2 11.6–17.3ROR 14.4 · χ² 1,157 / p 6e-254 | 14.0 EB05 11.8 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious PRR 10.6 · 91% clinician | no trial data cached |
| Acute myeloid leukaemia | 57 | 13.4 10.4–17.4ROR 13.6 · χ² 642 / p 5e-142 | 13.2 EB05 10.5 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious PRR 9.9 · 90% clinician | no trial data cached |
| Ovarian cyst | 33 | 12.0 8.6–16.9ROR 12.1 · χ² 322 / p 2e-72 | 11.6 EB05 8.4 · IC025 +2.8 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 9.5 | no trial data cached |
| Osteomyelitis | 59 | 12.0 9.3–15.4ROR 12.1 · χ² 581 / p 1e-128 | 11.7 EB05 9.3 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 9.1 · 95% clinician | no trial data cached |
| Neoplasm progression | 114 | 11.9 9.9–14.3ROR 12.1 · χ² 1,128 / p 1e-247 | 11.8 EB05 10.0 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious PRR 11.2 | no trial data cached |
| Ovarian cancer | 27 | 10.7 7.3–15.6ROR 10.7 · χ² 227 / p 1e-51 | 10.0 EB05 6.9 · IC025 +2.5 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 8.0 · 91% clinician | no trial data cached |
| Mitral valve incompetence | 31 | 10.1 7.1–14.3ROR 10.1 · χ² 243 / p 4e-55 | 9.4 EB05 6.7 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 7.5 | no trial data cached |
| Metastases to central nervous system | 35 | 10.0 7.2–14.0ROR 10.1 · χ² 275 / p 5e-62 | 9.4 EB05 6.9 · IC025 +2.6 3/3 methods agree | Labeled (related wording) related wording | serious PRR 7.1 | no trial data cached |
| Osteopenia | 41 | 9.9 7.3–13.4ROR 9.9 · χ² 317 / p 3e-71 | 9.3 EB05 7.0 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 8.5 | no trial data cached |
| Hot flush (hot flashes) | 198 | 9.6 8.4–11.1ROR 9.9 · χ² 1,526 / p <1e-300 | 9.5 EB05 8.4 · IC025 +3.0 3/3 methods agree | Labeled (related wording) related wording | serious PRR 11.2 | no trial data cached |
| Malignant neoplasm progression | 266 | 9.6 8.5–10.8ROR 10.0 · χ² 2,041 / p <1e-300 | 9.5 EB05 8.6 · IC025 +3.0 3/3 methods agree | Reporting / coding artifact | serious PRR 7.3 | no trial data cached |
| Breast cancer female | 69 | 9.4 7.4–11.9ROR 9.5 · χ² 510 / p 3e-113 | 9.1 EB05 7.4 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious PRR 6.5 | no trial data cached |
| Dental caries | 27 | 9.0 6.2–13.1ROR 9.0 · χ² 183 / p 6e-42 | 8.2 EB05 5.8 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 9.9 | no trial data cached |
| Vaginal discharge | 24 | 8.8 5.9–13.1ROR 8.8 · χ² 157 / p 2e-36 | 7.9 EB05 5.4 · IC025 +2.2 3/3 methods agree | Labeled adverse reaction exact term | serious n=11 | no trial data cached |
| Breast cancer | 221 | 8.6 7.6–9.8ROR 8.9 · χ² 1,484 / p <1e-300 | 8.5 EB05 7.6 · IC025 +2.9 3/3 methods agree | Labeled — boxed warning exact term | serious PRR 6.3 | no trial data cached |
| Myelodysplastic syndrome | 34 | 8.6 6.2–12.1ROR 8.7 · χ² 221 / p 3e-50 | 8.0 EB05 5.9 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious PRR 6.5 · 90% clinician | no trial data cached |
| Hepatic steatosis | 43 | 8.5 6.3–11.4ROR 8.5 · χ² 276 / p 3e-62 | 8.0 EB05 6.1 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 6.2 | no trial data cached |
| Pain in jaw | 63 | 8.2 6.4–10.4ROR 8.2 · χ² 388 / p 1e-86 | 7.8 EB05 6.3 · IC025 +2.5 3/3 methods agree | Labeled (related wording) related wording | serious PRR 9.4 · 94% clinician | no trial data cached |
| Ejection fraction decreased | 33 | 7.8 5.5–10.9ROR 7.8 · χ² 188 / p 5e-43 | 7.2 EB05 5.3 · IC025 +2.2 3/3 methods agree | Lab value / disease marker | serious PRR 6.4 | no trial data cached |
| Tooth disorder | 45 | 7.4 5.5–9.9ROR 7.4 · χ² 242 / p 8e-55 | 6.9 EB05 5.4 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 8.7 | no trial data cached |
| Impaired healing | 64 | 7.1 5.6–9.1ROR 7.2 · χ² 332 / p 2e-74 | 6.8 EB05 5.5 · IC025 +2.4 3/3 methods agree | Reporting / coding artifact | serious PRR 6.1 | no trial data cached |
| Tenderness | 20 | 7.0 4.5–10.9ROR 7.0 · χ² 97 / p 3e-23 | 6.2 EB05 4.2 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious n=19 | no trial data cached |
| Hypercholesterolaemia | 18 | 6.9 4.3–10.9ROR 6.9 · χ² 85 / p 2e-20 | 6.0 EB05 4.0 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious PRR 5.5 | no trial data cached |
| Hypercalcaemia | 22 | 6.5 4.3–9.9ROR 6.6 · χ² 98 / p 2e-23 | 5.8 EB05 4.0 · IC025 +1.8 3/3 methods agree | Labeled — boxed warning exact term | serious PRR 5.0 | no trial data cached |
| Bone pain | 104 | 6.5 5.4–7.9ROR 6.6 · χ² 479 / p 1e-106 | 6.3 EB05 5.4 · IC025 +2.3 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 6.5 | no trial data cached |
| Carpal tunnel syndrome | 24 | 6.3 4.2–9.3ROR 6.3 · χ² 101 / p 5e-24 | 5.6 EB05 4.0 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious PRR 5.3 | no trial data cached |
| Sinus bradycardia | 16 | 6.1 3.7–9.9ROR 6.1 · χ² 63 / p 1e-15 | 5.2 EB05 3.4 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 4.7 | no trial data cached |
| Atelectasis | 16 | 6.0 3.7–9.9ROR 6.1 · χ² 62 / p 1e-15 | 5.2 EB05 3.4 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 4.6 | no trial data cached |
| Osteoarthritis | 69 | 6.0 4.7–7.5ROR 6.0 · χ² 280 / p 4e-63 | 5.7 EB05 4.7 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious PRR 4.8 | no trial data cached |
| Disease progression | 189 | 5.9 5.1–6.8ROR 6.0 · χ² 763 / p 3e-168 | 5.8 EB05 5.1 · IC025 +2.3 3/3 methods agree | Reporting / coding artifact | serious PRR 4.2 | no trial data cached |
| Hyperlipidaemia | 19 | 5.8 3.7–9.1ROR 5.8 · χ² 71 / p 2e-17 | 5.1 EB05 3.5 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 4.5 | no trial data cached |
| Myocardial ischaemia | 17 | 5.4 3.4–8.7ROR 5.4 · χ² 57 / p 2e-14 | 4.8 EB05 3.2 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 4.1 | no trial data cached |
| Gingival bleeding | 20 | 5.4 3.5–8.3ROR 5.4 · χ² 67 / p 2e-16 | 4.8 EB05 3.3 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 5.4 | no trial data cached |
Trial evidence (ClinicalTrials.gov)
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 |
|---|---|---|---|---|---|---|
| Fatigue (tiredness) | 396 | 1.9 1.7–2.1ROR 1.9 · χ² 165 / p 6e-38 | 1.9 EB05 1.7 · IC025 +0.7 | Labeled adverse reaction exact term | serious PRR 1.9 | no trial data cached |
| Arthralgia (joint pain) | 277 | 2.4 2.2–2.7ROR 2.5 · χ² 241 / p 1e-54 | 2.4 EB05 2.2 · IC025 +1.1 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.4 | no trial data cached |
| Malignant neoplasm progression | 266 | 9.6 8.5–10.8ROR 10.0 · χ² 2,041 / p <1e-300 | 9.5 EB05 8.6 · IC025 +3.0 3/3 methods agree | Reporting / coding artifact | serious PRR 7.3 | no trial data cached |
| Breast cancer | 221 | 8.6 7.6–9.8ROR 8.9 · χ² 1,484 / p <1e-300 | 8.5 EB05 7.6 · IC025 +2.9 3/3 methods agree | Labeled — boxed warning exact term | serious PRR 6.3 | no trial data cached |
| Hot flush (hot flashes) | 198 | 9.6 8.4–11.1ROR 9.9 · χ² 1,526 / p <1e-300 | 9.5 EB05 8.4 · IC025 +3.0 3/3 methods agree | Labeled (related wording) related wording | serious PRR 11.2 | no trial data cached |
| Disease progression | 189 | 5.9 5.1–6.8ROR 6.0 · χ² 763 / p 3e-168 | 5.8 EB05 5.1 · IC025 +2.3 3/3 methods agree | Reporting / coding artifact | serious PRR 4.2 | no trial data cached |
| Metastases to bone | 181 | 41.0 35.5–47.3ROR 42.3 · χ² 6,942 / p <1e-300 | 40.3 EB05 35.7 · IC025 +4.9 3/3 methods agree | Labeled (related wording) related wording | serious PRR 29.9 | no trial data cached |
| Pain in extremity | 175 | 2.2 1.9–2.5ROR 2.2 · χ² 111 / p 3e-26 | 2.2 EB05 1.9 · IC025 +0.9 | Not in label — unassessed | serious PRR 2.3 | no trial data cached |
| Depression | 164 | 2.6 2.3–3.1ROR 2.7 · χ² 166 / p 3e-38 | 2.6 EB05 2.3 · IC025 +1.1 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.3 | no trial data cached |
| Back pain | 158 | 2.5 2.1–2.9ROR 2.5 · χ² 141 / p 9e-33 | 2.5 EB05 2.2 · IC025 +1.0 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.7 | no trial data cached |
| Fall | 152 | 1.7 1.4–2.0ROR 1.7 · χ² 41 / p 7e-11 | 1.7 EB05 1.5 · IC025 +0.5 | Not in label — unassessed | serious PRR 1.3 | no trial data cached |
| Insomnia (trouble sleeping) | 152 | 2.1 1.8–2.4ROR 2.1 · χ² 86 / p 9e-21 | 2.1 EB05 1.8 · IC025 +0.8 | Labeled adverse reaction exact term | serious PRR 2.1 | no trial data cached |
| Myalgia (muscle pain) | 138 | 3.0 2.5–3.5ROR 3.0 · χ² 180 / p 2e-41 | 2.9 EB05 2.6 · IC025 +1.3 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.8 | no trial data cached |
| Osteonecrosis (bone death) | 136 | 15.1 12.8–17.8ROR 15.4 · χ² 1,769 / p <1e-300 | 15.0 EB05 13.0 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious PRR 11.0 · 100% clinician | no trial data cached |
| Weight increased (weight gain) | 132 | 2.2 1.8–2.6ROR 2.2 · χ² 83 / p 4e-20 | 2.2 EB05 1.9 · IC025 +0.8 | Labeled (related wording) related wording | serious PRR 1.8 | 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.
- Metastases to lung — n=71, PRR 22.7
- Tooth extraction — n=62, PRR 18.3
- Osteonecrosis — n=136, PRR 15.1
- Osteonecrosis of jaw — n=96, PRR 14.2
- Acute myeloid leukaemia — n=57, PRR 13.4
- Osteomyelitis — n=59, PRR 12.0
- Neoplasm progression — n=114, PRR 11.9
- Mitral valve incompetence — n=31, PRR 10.1
- Osteopenia — n=41, PRR 9.9
- Breast cancer female — n=69, PRR 9.4
✓ A hand-written Bradford Hill causality assessment exists for this drug: Tamoxifen ↔ Venous thromboembolism.
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 Tamoxifen?
In FDA FAERS, the most frequently co-reported reaction terms for Tamoxifen are fatigue, arthralgia, breast cancer, hot flush, metastases to bone, pain in extremity. 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 Tamoxifen have an FDA boxed warning?
Yes. The current FDA label carries a boxed warning: - For Women with Ductal Carcinoma in Situ (DCIS) and Women at High Risk for Breast Cancer : Serious and life-threatening events associated with tamoxifen citrate in the risk reduction setting (women at high risk for cancer and women with DCIS) include uterine malignancies, stroke and pulmonary embolism.
Do FAERS signals prove that Tamoxifen 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 509f8ba3-214d-aec8-e063-6294a90af498, effective 20260430; matched on
openfda.generic_name.exact:"TAMOXIFEN CITRATE") - 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, 442 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.