Drug · FAERS side-effect profile with label screen

Mexiletine side effects: what 420 FDA adverse event reports show

Mexiletine Hydrochloride · 12 reaction terms · 170 drug–reaction co-reports · data 2026-09-14

Drug class

Not stated in label

Label matched

Mexiletine Hydrochloride (Mexiletine Hydrochloride)

closest FDA label found for this product string; brand list suppressed because the label is a related product, not an exact match

Who reports

420 reports · 91% serious · 76 with death outcome · 41% female

openFDA FAERS counts, all years, deduplication not applied

Used for

Mexiletine Hydrochloride Capsules USP are indicated for the treatment of documented ventricular arrhythmias, such as sustained ventricular tachycardia, that, in the judgment of the physician, are life- threatening. Because of the proarrhythmic effects of mexiletine, its use with lesser arrhythmias is generally not recommended.

FDA label, Indications and Usage

What it is

DESCRIPTION Mexiletine hydrochloride USP is an orally active antiarrhythmic agent. It is a white to off-white crystalline powder with slightly bitter taste, freely soluble in water and in alcohol. Mexiletine hydrochloride USP has a pKa of 9.2.

FDA label, Description section

Boxed warning

WARNINGS Mortality In the National Heart, Lung and Blood Institute’s Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multicentered, randomized, double-blind study in patients with asymptomatic non-life-thre.

FDA 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 10 strongest signals

Likely indication confounding 2Reporting / coding artifact 1Lab value / disease marker 2Not in label — unassessed 5

What the badges mean

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. 2 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
Ventricular tachycardia	31	93.6 66.7–131.3ROR 100.9 · χ² 2,744 / p <1e-300	88.4 EB05 65.3 · IC025 +4.6 3/3 methods agree	Likely indication confounding term in indications	serious PRR 59.5	no trial data cached
Impaired quality of life	22	76.4 50.9–114.9ROR 80.6 · χ² 1,562 / p <1e-300	71.8 EB05 50.0 · IC025 +4.1 3/3 methods agree	Not in label — unassessed	serious PRR 71.6 · ♀ 100% (drug 41%) · 100% clinician	no trial data cached
Poor quality sleep	24	56.1 38.0–82.7ROR 59.4 · χ² 1,243 / p 1e-272	53.7 EB05 38.0 · IC025 +4.0 3/3 methods agree	Reporting / coding artifact	serious PRR 65.1 · ♀ 100% (drug 41%) · 100% clinician	no trial data cached
Impaired work ability	23	53.6 36.0–79.8ROR 56.6 · χ² 1,135 / p 4e-249	51.4 EB05 36.1 · IC025 +4.0 3/3 methods agree	Not in label — unassessed	serious PRR 43.3 · ♀ 100% (drug 41%) · 100% clinician	no trial data cached
Hyperlipidaemia	12	50.0 28.6–87.4ROR 51.5 · χ² 528 / p 3e-117	46.5 EB05 28.4 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 31.9	no trial data cached
Ventricular fibrillation	8	35.9 18.1–71.3ROR 36.6 · χ² 237 / p 7e-54	33.2 EB05 17.9 · IC025 +2.3 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious PRR 22.7	no trial data cached
Gamma-glutamyltransferase increased	13	29.3 17.1–50.0ROR 30.2 · χ² 327 / p 2e-73	28.2 EB05 17.4 · IC025 +2.9 3/3 methods agree	Lab value / disease marker	serious PRR 19.3	no trial data cached
Drug eruption	10	28.3 15.4–52.3ROR 29.0 · χ² 237 / p 8e-54	26.9 EB05 15.4 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 20.6	no trial data cached
Oral herpes	10	25.7 13.9–47.4ROR 26.3 · χ² 213 / p 1e-48	24.4 EB05 13.8 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 38.0	no trial data cached
Bone density decreased	10	15.8 8.5–29.1ROR 16.1 · χ² 124 / p 4e-29	14.2 EB05 7.1 · IC025 +2.1 3/3 methods agree	Lab value / disease marker	serious PRR 12.4	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
Ventricular tachycardia	31	93.6 66.7–131.3ROR 100.9 · χ² 2,744 / p <1e-300	88.4 EB05 65.3 · IC025 +4.6 3/3 methods agree	Likely indication confounding term in indications	serious PRR 59.5	no trial data cached
Poor quality sleep	24	56.1 38.0–82.7ROR 59.4 · χ² 1,243 / p 1e-272	53.7 EB05 38.0 · IC025 +4.0 3/3 methods agree	Reporting / coding artifact	serious PRR 65.1 · ♀ 100% (drug 41%) · 100% clinician	no trial data cached
Impaired work ability	23	53.6 36.0–79.8ROR 56.6 · χ² 1,135 / p 4e-249	51.4 EB05 36.1 · IC025 +4.0 3/3 methods agree	Not in label — unassessed	serious PRR 43.3 · ♀ 100% (drug 41%) · 100% clinician	no trial data cached
Impaired quality of life	22	76.4 50.9–114.9ROR 80.6 · χ² 1,562 / p <1e-300	71.8 EB05 50.0 · IC025 +4.1 3/3 methods agree	Not in label — unassessed	serious PRR 71.6 · ♀ 100% (drug 41%) · 100% clinician	no trial data cached
Gamma-glutamyltransferase increased	13	29.3 17.1–50.0ROR 30.2 · χ² 327 / p 2e-73	28.2 EB05 17.4 · IC025 +2.9 3/3 methods agree	Lab value / disease marker	serious PRR 19.3	no trial data cached
Hyperlipidaemia	12	50.0 28.6–87.4ROR 51.5 · χ² 528 / p 3e-117	46.5 EB05 28.4 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 31.9	no trial data cached
Bone density decreased	10	15.8 8.5–29.1ROR 16.1 · χ² 124 / p 4e-29	14.2 EB05 7.1 · IC025 +2.1 3/3 methods agree	Lab value / disease marker	serious PRR 12.4	no trial data cached
Oral herpes	10	25.7 13.9–47.4ROR 26.3 · χ² 213 / p 1e-48	24.4 EB05 13.8 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 38.0	no trial data cached
Drug eruption	10	28.3 15.4–52.3ROR 29.0 · χ² 237 / p 8e-54	26.9 EB05 15.4 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 20.6	no trial data cached
Ventricular fibrillation	8	35.9 18.1–71.3ROR 36.6 · χ² 237 / p 7e-54	33.2 EB05 17.9 · IC025 +2.3 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious PRR 22.7	no trial data cached
Neuroleptic malignant syndrome	4	16.8 6.3–44.6ROR 16.9 · χ² 45 / p 1e-11	10.9 EB05 3.2 · IC025 +0.8 3/3 methods agree	Not in label — unassessed	serious PRR 10.6	no trial data cached
Gastric cancer	3	5.8 1.9–18.1ROR 5.9 · χ² 8 / p 0.003	3.5 EB05 1.4 · IC025 -0.3 PRR-only: not supported by EBGM or IC	Not in label — unassessed	serious PRR 3.7	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.

Impaired quality of life — n=22, PRR 76.4
Impaired work ability — n=23, PRR 53.6

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 Mexiletine?

In FDA FAERS, the most frequently co-reported reaction terms for Mexiletine are ventricular tachycardia, impaired work ability, impaired quality of life, gamma-glutamyltransferase increased, hyperlipidaemia, bone density decreased. 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 Mexiletine have an FDA boxed warning?

Yes. The current FDA label carries a boxed warning: WARNINGS Mortality In the National Heart, Lung and Blood Institute’s Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multicentered, randomized, double-blind study in patients with asymptomatic non-life-thre.

Do FAERS signals prove that Mexiletine 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 1b3a807f-368a-42dc-8266-ddf8347a8826, effective 20251107; matched on openfda.generic_name.exact:"MEXILETINE HYDROCHLORIDE")
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, 12 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.