Drug · FAERS side-effect profile with label screen
Letrozole Tablets side effects: what 47,818 FDA adverse event reports show
Who reports
47,818 reports · 80% serious · 4,408 with death outcome · 98% female
openFDA FAERS counts, all years, deduplication not applied
Used for
Letrozole tablets are an aromatase inhibitor indicated for: Adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer (1.1) Extended adjuvant treatment of postmenopausal women with early breast cancer who have receiv.
FDA label, Indications and Usage
What it is
Letrozole Tablets USP for oral administration contain 2.5 mg of letrozole, USP, a nonsteroidal aromatase inhibitor (inhibitor of estrogen synthesis). It is chemically described as 4,4'-(1 H -1,2,4triazol-1-ylmethylene)dibenzonitrile, and its structural formula is: C 17 H 11 N 5 M.W.
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) 1Likely indication confounding 2Lab value / disease marker 8Not in label — unassessed 29
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.
- 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.
- 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, for the 300 most-reported drugs, adjusted for age band), and flags pairs whose reports are unusually skewed by sex or come mostly from consumers. Each row also shows the PRR against the other drugs of the same FDA class, which removes most confounding by the condition being treated, and a calibrated p-value: on validation, known non-causes average an ROR of about 2, so significance is judged against that empirical null (✓ = p < 0.05 after calibration). 1,199 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
Show:
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Serous cystadenocarcinoma ovary | 26 | 561.2 313.3–1,005.2ROR 561.5 · calibrated p 1e-12 ✓ | 207.4 EB05 148.8 · IC025 +4.8 3/3 methods agree vs other Aromatase Inhibitors: only this drug | Not in label — unassessed | serious n=26 | not reported in cached trials |
| Pik3ca-activated mutation | 168 | 470.9 378.5–585.9ROR 472.6 · calibrated p 2e-13 ✓ | 220.1 EB05 193.6 · IC025 +6.8 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.9 (1.5–2.2) | Not in label — unassessed | serious n=168 | not reported in cached trials |
| Hormone receptor positive her2 negative breast cancer | 134 | 328.7 262.6–411.4ROR 329.6 · calibrated p 7e-12 ✓ | 182.2 EB05 157.7 · IC025 +6.5 3/3 methods agree vs other Aromatase Inhibitors: PRR 3.2 (2.5–4.0) | Labeled (related wording) related wording | serious n=134 | not reported in cached trials |
| Carbohydrate antigen 15-3 increased | 255 | 221.5 190.5–257.5ROR 222.7 · calibrated p 2e-10 ✓ | 145.1 EB05 130.8 · IC025 +6.6 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.9 (1.6–2.1) | Lab value / disease marker | serious n=249 | not reported in cached trials |
| Hormone receptor positive breast cancer | 57 | 121.2 90.4–162.6ROR 121.4 · calibrated p 5e-8 ✓ | 92.0 EB05 73.7 · IC025 +5.3 3/3 methods agree vs other Aromatase Inhibitors: PRR 2.2 (1.6–3.0) | Likely indication confounding term in indications; also in warnings | serious n=57 | not reported in cached trials |
| Amaurosis fugax | 230 | 120.2 103.9–139.1ROR 120.8 · calibrated p 3e-8 ✓ | 93.5 EB05 83.8 · IC025 +6.1 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.0 (0.9–1.2) | Not in label — unassessed | serious n=230 · 93% clinician | not reported in cached trials |
| Body surface area increased | 25 | 104.8 67.7–162.2ROR 104.8 · calibrated p 3e-7 ✓ | 79.5 EB05 56.7 · IC025 +4.3 3/3 methods agree vs other Aromatase Inhibitors: only this drug | Not in label — unassessed | serious n=24 | not reported in cached trials |
| Pleural neoplasm | 30 | 97.4 65.5–144.7ROR 97.4 · calibrated p 4e-7 ✓ | 75.9 EB05 55.7 · IC025 +4.5 3/3 methods agree vs other Aromatase Inhibitors: PRR 3.0 (1.9–4.8) | Not in label — unassessed | serious n=30 · 100% clinician | not reported in cached trials |
| Carbohydrate antigen 27.29 increased | 25 | 87.0 56.6–133.7ROR 87.1 · calibrated p 1e-6 ✓ | 68.9 EB05 49.1 · IC025 +4.2 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.7 (1.0–2.7) | Lab value / disease marker | – | not reported in cached trials |
| Breast cancer metastatic | 1,679 | 81.4 77.3–85.6ROR 84.3 · calibrated p 4e-7 ✓ | 68.6 EB05 65.9 · IC025 +6.0 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.8 (1.7–1.9) | Likely indication confounding term in indications; also in warnings | serious PRR 49.0 | not reported in cached trials |
| Metastases to chest wall | 54 | 80.9 60.5–108.2ROR 81.0 · calibrated p 9e-7 ✓ | 66.8 EB05 53.1 · IC025 +4.9 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.3 (1.0–1.8) | Not in label — unassessed | serious n=54 | not reported in cached trials |
| Metastases to abdominal wall | 28 | 74.6 50.0–111.4ROR 74.7 · calibrated p 2e-6 ✓ | 61.2 EB05 44.5 · IC025 +4.3 3/3 methods agree vs other Aromatase Inhibitors: only this drug | Not in label — unassessed | serious n=28 · 100% clinician | not reported in cached trials |
| Pseudocirrhosis | 46 | 71.4 52.3–97.6ROR 71.5 · calibrated p 2e-6 ✓ | 60.0 EB05 46.8 · IC025 +4.7 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.1 (0.8–1.5) | Not in label — unassessed | serious n=46 · 100% clinician | not reported in cached trials |
| Tumour marker abnormal | 45 | 67.9 49.6–93.0ROR 68.0 · calibrated p 3e-6 ✓ | 57.5 EB05 44.7 · IC025 +4.7 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.7 (1.2–2.5) | Lab value / disease marker | serious n=35 | not reported in cached trials |
| Metastases to skin | 133 | 65.4 54.5–78.5ROR 65.6 · calibrated p 3e-6 ✓ | 56.5 EB05 48.9 · IC025 +5.3 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.5 (1.3–1.9) | Not in label — unassessed | serious n=132 | not reported in cached trials |
| Metastases to pleura | 133 | 64.1 53.5–76.9ROR 64.3 · calibrated p 3e-6 ✓ | 55.6 EB05 48.1 · IC025 +5.2 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.6 (1.3–2.0) | Not in label — unassessed | serious n=133 | not reported in cached trials |
| Metastases to the mediastinum | 52 | 62.7 46.9–83.9ROR 62.8 · calibrated p 5e-6 ✓ | 53.9 EB05 42.7 · IC025 +4.7 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.3 (1.0–1.8) | Not in label — unassessed | serious n=52 · 100% clinician | not reported in cached trials |
| Invasive lobular breast carcinoma | 62 | 60.3 46.2–78.6ROR 60.4 · calibrated p 6e-6 ✓ | 52.2 EB05 42.2 · IC025 +4.8 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.6 (1.2–2.2) | Not in label — unassessed | serious n=60 | not reported in cached trials |
| Metastases to bone | 1,850 | 55.9 53.3–58.6ROR 58.1 · calibrated p 5e-6 ✓ | 49.6 EB05 47.7 · IC025 +5.5 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.4 (1.4–1.5) | Not in label — unassessed | serious PRR 35.9 | not reported in cached trials |
| Metastases to thorax | 26 | 49.9 33.2–74.9ROR 49.9 · calibrated p 3e-5 ✓ | 43.5 EB05 31.2 · IC025 +4.0 3/3 methods agree vs other Aromatase Inhibitors: PRR 0.9 (0.6–1.4) | Not in label — unassessed | serious n=26 | not reported in cached trials |
| Invasive breast carcinoma | 42 | 49.5 36.0–68.2ROR 49.6 · calibrated p 2e-5 ✓ | 43.7 EB05 33.7 · IC025 +4.4 3/3 methods agree vs other Aromatase Inhibitors: PRR 2.7 (1.8–4.0) | Not in label — unassessed | serious n=42 · 100% clinician | not reported in cached trials |
| Bone marrow infiltration | 38 | 47.8 34.2–66.9ROR 47.9 · calibrated p 3e-5 ✓ | 42.3 EB05 32.2 · IC025 +4.3 3/3 methods agree vs other Aromatase Inhibitors: PRR 2.7 (1.8–4.0) | Not in label — unassessed | serious n=38 · 100% clinician | not reported in cached trials |
| Metastases to pelvis | 60 | 46.0 35.3–60.0ROR 46.1 · calibrated p 3e-5 ✓ | 41.2 EB05 33.1 · IC025 +4.5 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.2 (0.9–1.6) | Not in label — unassessed | serious n=60 | not reported in cached trials |
| Neutrophil percentage decreased | 47 | 42.4 31.5–57.3ROR 42.5 · calibrated p 5e-5 ✓ | 38.2 EB05 29.9 · IC025 +4.3 3/3 methods agree vs other Aromatase Inhibitors: PRR 3.6 (2.4–5.4) | Lab value / disease marker | serious n=46 · 100% consumer | not reported in cached trials |
| Tumour marker increased | 416 | 41.5 37.5–45.8ROR 41.8 · calibrated p 4e-5 ✓ | 37.8 EB05 34.9 · IC025 +5.0 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.4 (1.2–1.5) | Lab value / disease marker | serious n=344 | not reported in cached trials |
| Breast cancer recurrent | 269 | 40.9 36.1–46.3ROR 41.1 · calibrated p 5e-5 ✓ | 37.3 EB05 33.7 · IC025 +4.9 3/3 methods agree vs other Aromatase Inhibitors: PRR 0.9 (0.8–1.1) | Not in label — unassessed | serious n=268 | not reported in cached trials |
| Metastases to stomach | 31 | 38.3 26.6–55.4ROR 38.4 · calibrated p 1e-4 ✓ | 34.6 EB05 25.5 · IC025 +3.9 3/3 methods agree vs other Aromatase Inhibitors: PRR 3.1 (1.9–5.0) | Not in label — unassessed | serious n=31 | not reported in cached trials |
| Intestinal metastasis | 28 | 37.9 25.8–55.8ROR 37.9 · calibrated p 1e-4 ✓ | 34.2 EB05 24.8 · IC025 +3.8 3/3 methods agree vs other Aromatase Inhibitors: only this drug | Not in label — unassessed | serious n=28 | not reported in cached trials |
| Lymphocyte percentage increased | 32 | 37.5 26.2–53.9ROR 37.6 · calibrated p 1e-4 ✓ | 34.0 EB05 25.2 · IC025 +3.9 3/3 methods agree vs other Aromatase Inhibitors: PRR 3.5 (2.2–5.6) | Lab value / disease marker | serious n=31 · 100% consumer | not reported in cached trials |
| Metastases to liver | 1,334 | 36.1 34.1–38.1ROR 37.1 · calibrated p 8e-5 ✓ | 33.3 EB05 31.9 · IC025 +5.0 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.5 (1.4–1.6) | Not in label — unassessed | serious PRR 24.0 | not reported in cached trials |
| Invasive ductal breast carcinoma | 205 | 35.7 30.9–41.1ROR 35.8 · calibrated p 1e-4 ✓ | 32.9 EB05 29.3 · IC025 +4.7 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.7 (1.4–2.0) | Not in label — unassessed | serious n=205 | not reported in cached trials |
| Breast conserving surgery | 38 | 35.1 25.2–48.9ROR 35.2 · calibrated p 2e-4 ✓ | 32.1 EB05 24.4 · IC025 +4.0 3/3 methods agree vs other Aromatase Inhibitors: PRR 3.6 (2.3–5.6) | Not in label — unassessed | serious n=38 · 100% consumer | not reported in cached trials |
| Metastases to spine | 237 | 33.3 29.2–38.0ROR 33.5 · calibrated p 2e-4 ✓ | 30.9 EB05 27.8 · IC025 +4.7 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.1 (0.9–1.2) | Not in label — unassessed | serious n=237 | not reported in cached trials |
| Neoplasm progression | 2,442 | 32.7 31.4–34.1ROR 34.4 · calibrated p 1e-4 ✓ | 30.5 EB05 29.5 · IC025 +4.9 3/3 methods agree vs other Aromatase Inhibitors: PRR 2.1 (2.0–2.2) | Not in label — unassessed | serious PRR 22.1 | not reported in cached trials |
| Metastases to bone marrow | 34 | 31.7 22.4–44.9ROR 31.7 · calibrated p 3e-4 ✓ | 29.2 EB05 21.8 · IC025 +3.8 3/3 methods agree vs other Aromatase Inhibitors: PRR 2.3 (1.5–3.5) | Not in label — unassessed | serious n=33 | not reported in cached trials |
| Carcinoembryonic antigen increased | 130 | 31.6 26.4–37.7ROR 31.7 · calibrated p 2e-4 ✓ | 29.4 EB05 25.4 · IC025 +4.4 3/3 methods agree vs other Aromatase Inhibitors: PRR 2.0 (1.6–2.5) | Lab value / disease marker | serious n=130 | not reported in cached trials |
| Metastases to lymph nodes | 442 | 30.9 28.1–34.0ROR 31.2 · calibrated p 2e-4 ✓ | 28.9 EB05 26.7 · IC025 +4.7 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.4 (1.3–1.6) | Not in label — unassessed | serious n=442 | not reported in cached trials |
| Bone lesion | 233 | 30.2 26.5–34.5ROR 30.4 · calibrated p 3e-4 ✓ | 28.2 EB05 25.3 · IC025 +4.5 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.3 (1.1–1.5) | Not in label — unassessed | serious n=226 | not reported in cached trials |
| Metastases to peritoneum | 153 | 28.5 24.2–33.5ROR 28.6 · calibrated p 4e-4 ✓ | 26.7 EB05 23.3 · IC025 +4.4 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.9 (1.6–2.4) | Not in label — unassessed | serious n=153 | not reported in cached trials |
| Mean cell haemoglobin increased | 100 | 28.1 22.9–34.4ROR 28.1 · calibrated p 4e-4 ✓ | 26.3 EB05 22.3 · IC025 +4.2 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.8 (1.4–2.3) | Lab value / disease marker | serious n=89 | not reported in cached trials |
Trial evidence (ClinicalTrials.gov)
✓ Trial adverse-event data found on ClinicalTrials.gov
Largest completed trials with posted results that list Letrozole Tablets as a study intervention. The right-hand column of the signal table shows whether each FAERS term was also recorded in these trials, with a real denominator (0 of 40 signal terms matched).
- NCT01272037 — Tamoxifen Citrate, Letrozole, Anastrozole, or Exemestane With or Without Chemotherapy in Treating Patients Wit (N=5018, PHASE3; 16 AE terms posted; arms: Chemo and Endocrine Therapy; Endocrine Therapy Alone)
- NCT00553410 — Letrozole in Preventing Cancer in Postmenopausal Women Who Have Received 4-6 Years of Hormone Therapy for Horm (N=4884, PHASE3; 225 AE terms posted; arms: Arm A: Continuous Letrozole; Arm B: Intermittent Letrozole)
Caveats: trial populations, doses and follow-up differ from the reporting population; AE terms are sponsor-coded and matched here by wording; absence from a trial list means the term was not reported above the sponsor's frequency threshold, not that it cannot occur.
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) | 6,045 | 3.4 3.4–3.5ROR 3.8 · calibrated p 0.420 | 3.4 EB05 3.3 · IC025 +1.7 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.6 (1.5–1.6) | Labeled adverse reaction exact term | serious PRR 3.2 | NCT00553410: 48/2,417 (2.0%) on Letrozole Tablets (serious AE) |
| Neutropenia (low neutrophils (infection-fighting cells)) | 4,547 | 15.2 14.8–15.6ROR 16.7 · calibrated p 0.004 ✓ | 14.7 EB05 14.4 · IC025 +3.8 3/3 methods agree vs other Aromatase Inhibitors: PRR 2.4 (2.3–2.5) | Not in label — unassessed | serious PRR 10.9 | NCT00553410: 1/2,417 (0.0%) on Letrozole Tablets (serious AE) |
| Nausea | 4,413 | 2.5 2.4–2.5ROR 2.6 · calibrated p 0.768 | 2.5 EB05 2.4 · IC025 +1.2 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.5 (1.4–1.5) | Labeled adverse reaction exact term | serious PRR 2.6 | NCT00553410: 2/2,417 (0.1%) on Letrozole Tablets (serious AE) |
| Diarrhoea (diarrhea) | 3,850 | 2.6 2.6–2.7ROR 2.8 · calibrated p 0.703 | 2.6 EB05 2.6 · IC025 +1.3 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.5 (1.4–1.5) | Labeled adverse reaction exact term | serious PRR 2.5 | NCT00553410: 5/2,417 (0.2%) on Letrozole Tablets (serious AE) |
| Malignant neoplasm progression | 3,601 | 16.0 15.5–16.6ROR 17.3 · calibrated p 0.004 ✓ | 15.5 EB05 15.1 · IC025 +3.9 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.6 (1.6–1.7) | Reporting / coding artifact | serious PRR 11.3 | not reported in cached trials |
| White blood cell count decreased | 3,246 | 13.5 13.0–14.0ROR 14.4 · calibrated p 0.008 ✓ | 13.1 EB05 12.7 · IC025 +3.7 3/3 methods agree vs other Aromatase Inhibitors: PRR 2.1 (2.0–2.2) | Labeled (related wording) related wording | serious PRR 8.7 | not reported in cached trials |
| Arthralgia (joint pain) | 2,958 | 3.1 3.0–3.3ROR 3.3 · calibrated p 0.540 | 3.1 EB05 3.0 · IC025 +1.6 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.1 (1.1–1.2) | Labeled adverse reaction exact term | serious PRR 3.2 | not reported in cached trials |
| Alopecia (hair loss) | 2,828 | 6.4 6.2–6.6ROR 6.7 · calibrated p 0.111 | 6.3 EB05 6.1 · IC025 +2.6 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.3 (1.3–1.4) | Labeled adverse reaction exact term | serious PRR 6.1 | not reported in cached trials |
| Neoplasm progression | 2,442 | 32.7 31.4–34.1ROR 34.4 · calibrated p 1e-4 ✓ | 30.5 EB05 29.5 · IC025 +4.9 3/3 methods agree vs other Aromatase Inhibitors: PRR 2.1 (2.0–2.2) | Not in label — unassessed | serious PRR 22.1 | not reported in cached trials |
| Asthenia (weakness) | 2,336 | 2.7 2.6–2.8ROR 2.8 · calibrated p 0.686 | 2.7 EB05 2.6 · IC025 +1.4 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.4 (1.3–1.5) | Labeled adverse reaction exact term | serious PRR 2.4 | NCT00553410: 48/2,417 (2.0%) on Letrozole Tablets (serious AE) |
| Dyspnoea (shortness of breath) | 2,321 | 1.8 1.7–1.9ROR 1.8 · calibrated p 0.856 | 1.8 EB05 1.7 · IC025 +0.8 vs other Aromatase Inhibitors: PRR 1.3 (1.3–1.4) | Labeled adverse reaction exact term | serious PRR 1.6 | NCT00553410: 5/2,417 (0.2%) on Letrozole Tablets (serious AE) |
| Pain | 2,196 | 1.6 1.5–1.6ROR 1.6 · calibrated p 0.703 | 1.6 EB05 1.5 · IC025 +0.6 vs other Aromatase Inhibitors: PRR 1.2 (1.2–1.3) | Labeled adverse reaction exact term | serious PRR 1.4 | NCT00553410: 1/2,411 (0.0%) on Letrozole Tablets (serious AE) |
| Vomiting | 2,158 | 2.0 1.9–2.1ROR 2.1 · calibrated p 0.982 | 2.0 EB05 1.9 · IC025 +0.9 vs other Aromatase Inhibitors: PRR 1.4 (1.3–1.5) | Labeled adverse reaction exact term | serious PRR 1.8 | NCT00553410: 1/2,417 (0.0%) on Letrozole Tablets (serious AE) |
| Decreased appetite (loss of appetite) | 1,961 | 3.7 3.6–3.9ROR 3.9 · calibrated p 0.406 | 3.7 EB05 3.6 · IC025 +1.8 3/3 methods agree vs other Aromatase Inhibitors: PRR 1.5 (1.4–1.6) | Labeled (related wording) related wording | serious PRR 3.4 | not reported in cached trials |
| Off label use (used outside approved label) | 1,935 | 1.0 0.9–1.0ROR 1.0 · calibrated p 0.291 | 1.0 EB05 0.9 · IC025 -0.1 PRR-only: not supported by EBGM or IC vs other Aromatase Inhibitors: PRR 1.6 (1.5–1.6) | Reporting / coding artifact | serious PRR 1.1 | not reported in cached trials |
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.
- Serous cystadenocarcinoma ovary — n=26, PRR 561.2
- Pik3ca-activated mutation — n=168, PRR 470.9
- Amaurosis fugax — n=230, PRR 120.2
- Body surface area increased — n=25, PRR 104.8
- Pleural neoplasm — n=30, PRR 97.4
- Metastases to chest wall — n=54, PRR 80.9
- Metastases to abdominal wall — n=28, PRR 74.6
- Pseudocirrhosis — n=46, PRR 71.4
- Metastases to skin — n=133, PRR 65.4
- Metastases to pleura — n=133, PRR 64.1
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 Letrozole Tablets?
In FDA FAERS, the most frequently co-reported reaction terms for Letrozole Tablets are fatigue, neutropenia, nausea, diarrhoea, white blood cell count decreased, arthralgia. 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 Letrozole Tablets have an FDA boxed warning?
No. The FDA label retrieved for Letrozole Tablets has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Letrozole Tablets 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 1524730f-e37d-478c-1956-b113b3ca42a8, effective 20251119; matched on
openfda.generic_name.exact:"LETROZOLE") - 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, 1,239 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 - ClinicalTrials.gov API v2 (query
LETROZOLE, results-bearing studies sorted by enrollment)
Page generated 2026-10-14. 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.