Acetaminophen side effects: what 1,909 FDA adverse event reports show
Drug class
Not stated in label
Who reports
1,909 reports · 22% serious · 40 with death outcome · 51% female
Used for
temporarily relieves minor aches and pains due to: headache muscular aches backache minor pain of arthritis the common cold toothache premenstrual and menstrual cramps temporarily reduces fever
Boxed warning
None in the current label
Causality screen of the 25 strongest signals
What the badges mean
- 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.
- 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. 19 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 |
|---|---|---|---|---|---|---|
| Product packaging issue | 38 | 45.1 32.9–61.9ROR 46.0 · χ² 1,590 / p <1e-300 | 44.0 EB05 33.5 · IC025 +4.3 3/3 methods agree | Reporting / coding artifact | serious n=1 · 97% consumer | no trial data cached |
| Drug administration error | 64 | 22.6 17.8–28.8ROR 23.4 · χ² 1,299 / p 8e-285 | 22.4 EB05 18.2 · IC025 +3.9 3/3 methods agree | Reporting / coding artifact | serious PRR 16.4 · 97% consumer | no trial data cached |
| Expired product administered | 59 | 19.5 15.2–25.1ROR 20.1 · χ² 1,019 / p 5e-224 | 19.4 EB05 15.6 · IC025 +3.6 3/3 methods agree | Reporting / coding artifact | serious n=4 · 100% consumer | no trial data cached |
| Extra dose administered | 57 | 15.7 12.2–20.3ROR 16.1 · χ² 770 / p 9e-170 | 15.6 EB05 12.4 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=1 · 100% consumer | no trial data cached |
| Accidental overdose | 39 | 11.7 8.6–16.0ROR 11.9 · χ² 372 / p 3e-83 | 11.3 EB05 8.4 · IC025 +2.8 3/3 methods agree | Reporting / coding artifact | serious PRR 18.2 · 87% consumer | no trial data cached |
| Acute hepatic failure | 13 | 10.5 6.1–18.1ROR 10.6 · χ² 102 / p 2e-24 | 8.9 EB05 5.1 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 27.6 | no trial data cached |
| Product physical issue | 19 | 10.5 6.7–16.4ROR 10.6 · χ² 153 / p 2e-35 | 9.4 EB05 6.0 · IC025 +2.3 3/3 methods agree | Reporting / coding artifact | – | no trial data cached |
| Retching | 20 | 10.3 6.7–16.0ROR 10.4 · χ² 159 / p 8e-37 | 9.3 EB05 6.0 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 2.7 · 100% consumer | no trial data cached |
| Psychomotor hyperactivity | 14 | 9.2 5.5–15.5ROR 9.3 · χ² 95 / p 1e-22 | 7.7 EB05 4.7 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 8.6 | no trial data cached |
| Drug prescribing error | 16 | 9.0 5.5–14.7ROR 9.1 · χ² 106 / p 3e-25 | 7.7 EB05 4.8 · IC025 +2.0 3/3 methods agree | Reporting / coding artifact | – | no trial data cached |
| Product taste abnormal | 11 | 9.0 5.0–16.2ROR 9.0 · χ² 70 / p 3e-17 | 7.2 EB05 4.1 · IC025 +1.7 3/3 methods agree | Reporting / coding artifact | serious n=1 | no trial data cached |
| Ear infection | 21 | 8.7 5.7–13.3ROR 8.8 · χ² 135 / p 1e-31 | 7.7 EB05 5.2 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious PRR 13.9 | no trial data cached |
| Therapeutic response unexpected | 32 | 7.8 5.5–11.0ROR 7.9 · χ² 183 / p 5e-42 | 7.2 EB05 5.3 · IC025 +2.2 3/3 methods agree | Reporting / coding artifact | 100% consumer | no trial data cached |
| Accidental exposure to product | 71 | 7.8 6.2–9.8ROR 8.1 · χ² 416 / p 9e-93 | 7.5 EB05 6.1 · IC025 +2.5 3/3 methods agree | Reporting / coding artifact | serious PRR 16.3 · 97% consumer | no trial data cached |
| Hypersomnia | 20 | 7.7 5.0–11.9ROR 7.7 · χ² 110 / p 6e-26 | 6.7 EB05 4.5 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 18.4 · 70% consumer | no trial data cached |
| Gastroenteritis viral | 12 | 7.3 4.1–12.8ROR 7.3 · χ² 59 / p 9e-15 | 5.9 EB05 3.5 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 15.2 | no trial data cached |
| Wrong technique in product usage process | 125 | 6.8 5.7–8.0ROR 7.2 · χ² 617 / p 1e-136 | 6.6 EB05 5.7 · IC025 +2.4 3/3 methods agree | Reporting / coding artifact | serious PRR 4.3 · 94% consumer | no trial data cached |
| Product use issue | 107 | 6.3 5.2–7.6ROR 6.6 · χ² 474 / p 2e-105 | 6.1 EB05 5.2 · IC025 +2.3 3/3 methods agree | Reporting / coding artifact | serious PRR 1.0 · 96% consumer | no trial data cached |
| Incorrect dose administered | 123 | 6.0 5.1–7.1ROR 6.3 · χ² 513 / p 6e-114 | 5.9 EB05 5.1 · IC025 +2.3 3/3 methods agree | Reporting / coding artifact | serious PRR 6.3 · 87% consumer | no trial data cached |
| Crying | 17 | 5.1 3.2–8.2ROR 5.2 · χ² 52 / p 2e-13 | 4.5 EB05 3.0 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 8.1 | no trial data cached |
| Abnormal behaviour | 18 | 5.0 3.1–7.8ROR 5.0 · χ² 53 / p 2e-13 | 4.4 EB05 3.0 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 7.0 | no trial data cached |
| Inappropriate schedule of drug administration | 32 | 4.9 3.5–6.9ROR 4.9 · χ² 95 / p 1e-22 | 4.6 EB05 3.4 · IC025 +1.6 3/3 methods agree | Reporting / coding artifact | serious PRR 5.6 · 84% consumer | no trial data cached |
| Drug effect incomplete | 15 | 4.5 2.7–7.4ROR 4.5 · χ² 37 / p 6e-10 | 4.0 EB05 2.6 · IC025 +1.1 3/3 methods agree | Reporting / coding artifact | – | no trial data cached |
| Intentional product misuse | 31 | 3.9 2.8–5.6ROR 4.0 · χ² 65 / p 4e-16 | 3.7 EB05 2.8 · IC025 +1.3 3/3 methods agree | Reporting / coding artifact | serious PRR 0.8 · 100% consumer | no trial data cached |
| Product quality issue | 48 | 3.9 3.0–5.2ROR 4.0 · χ² 102 / p 3e-24 | 3.8 EB05 3.0 · IC025 +1.4 3/3 methods agree | Reporting / coding artifact | serious PRR 26.0 · 91% consumer | 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 |
|---|---|---|---|---|---|---|
| Wrong technique in product usage process | 125 | 6.8 5.7–8.0ROR 7.2 · χ² 617 / p 1e-136 | 6.6 EB05 5.7 · IC025 +2.4 3/3 methods agree | Reporting / coding artifact | serious PRR 4.3 · 94% consumer | no trial data cached |
| Incorrect dose administered | 123 | 6.0 5.1–7.1ROR 6.3 · χ² 513 / p 6e-114 | 5.9 EB05 5.1 · IC025 +2.3 3/3 methods agree | Reporting / coding artifact | serious PRR 6.3 · 87% consumer | no trial data cached |
| Product use issue | 107 | 6.3 5.2–7.6ROR 6.6 · χ² 474 / p 2e-105 | 6.1 EB05 5.2 · IC025 +2.3 3/3 methods agree | Reporting / coding artifact | serious PRR 1.0 · 96% consumer | no trial data cached |
| Accidental exposure to product | 71 | 7.8 6.2–9.8ROR 8.1 · χ² 416 / p 9e-93 | 7.5 EB05 6.1 · IC025 +2.5 3/3 methods agree | Reporting / coding artifact | serious PRR 16.3 · 97% consumer | no trial data cached |
| Drug administration error | 64 | 22.6 17.8–28.8ROR 23.4 · χ² 1,299 / p 8e-285 | 22.4 EB05 18.2 · IC025 +3.9 3/3 methods agree | Reporting / coding artifact | serious PRR 16.4 · 97% consumer | no trial data cached |
| Expired product administered | 59 | 19.5 15.2–25.1ROR 20.1 · χ² 1,019 / p 5e-224 | 19.4 EB05 15.6 · IC025 +3.6 3/3 methods agree | Reporting / coding artifact | serious n=4 · 100% consumer | no trial data cached |
| Extra dose administered | 57 | 15.7 12.2–20.3ROR 16.1 · χ² 770 / p 9e-170 | 15.6 EB05 12.4 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=1 · 100% consumer | no trial data cached |
| Product quality issue | 48 | 3.9 3.0–5.2ROR 4.0 · χ² 102 / p 3e-24 | 3.8 EB05 3.0 · IC025 +1.4 3/3 methods agree | Reporting / coding artifact | serious PRR 26.0 · 91% consumer | no trial data cached |
| Accidental overdose | 39 | 11.7 8.6–16.0ROR 11.9 · χ² 372 / p 3e-83 | 11.3 EB05 8.4 · IC025 +2.8 3/3 methods agree | Reporting / coding artifact | serious PRR 18.2 · 87% consumer | no trial data cached |
| Product packaging issue | 38 | 45.1 32.9–61.9ROR 46.0 · χ² 1,590 / p <1e-300 | 44.0 EB05 33.5 · IC025 +4.3 3/3 methods agree | Reporting / coding artifact | serious n=1 · 97% consumer | no trial data cached |
| Inappropriate schedule of drug administration | 32 | 4.9 3.5–6.9ROR 4.9 · χ² 95 / p 1e-22 | 4.6 EB05 3.4 · IC025 +1.6 3/3 methods agree | Reporting / coding artifact | serious PRR 5.6 · 84% consumer | no trial data cached |
| Therapeutic response unexpected | 32 | 7.8 5.5–11.0ROR 7.9 · χ² 183 / p 5e-42 | 7.2 EB05 5.3 · IC025 +2.2 3/3 methods agree | Reporting / coding artifact | 100% consumer | no trial data cached |
| Intentional product misuse | 31 | 3.9 2.8–5.6ROR 4.0 · χ² 65 / p 4e-16 | 3.7 EB05 2.8 · IC025 +1.3 3/3 methods agree | Reporting / coding artifact | serious PRR 0.8 · 100% consumer | no trial data cached |
| Ear infection | 21 | 8.7 5.7–13.3ROR 8.8 · χ² 135 / p 1e-31 | 7.7 EB05 5.2 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious PRR 13.9 | no trial data cached |
| Hypersomnia | 20 | 7.7 5.0–11.9ROR 7.7 · χ² 110 / p 6e-26 | 6.7 EB05 4.5 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 18.4 · 70% consumer | 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.
- Extra dose administered — n=57, PRR 15.7
- Retching — n=20, PRR 10.3
- Ear infection — n=21, PRR 8.7
- Hypersomnia — n=20, PRR 7.7
✓ A hand-written Bradford Hill causality assessment exists for this drug: Acetaminophen (paracetamol) ↔ Liver injury / hepatotoxicity.
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 Acetaminophen?
In FDA FAERS, the most frequently co-reported reaction terms for Acetaminophen are extra dose administered, ear infection, hypersomnia. 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 Acetaminophen have an FDA boxed warning?
No. The FDA label retrieved for Acetaminophen has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Acetaminophen 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 004c39cd-b4f4-1cae-e063-6394a90a0697, effective 20251003; matched on
openfda.generic_name.exact:"ACETAMINOPHEN") - 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, 44 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.