Meclizine Hydrochloride side effects: what 19,461 FDA adverse event reports show
Drug class
Not stated in label
Brand names
Meclizine Hydrochloride
Who reports
19,461 reports · 62% serious · 1,695 with death outcome · 74% female
Used for
Meclizine hydrochloride tablets are indicated for the treatment of vertigo associated with diseases affecting the vestibular system in adults. Meclizine hydrochloride tablets are indicated for the treatment of vertigo associated with diseases affecting the vestibular system in adults ( 1 ).
What it is
Meclizine hydrochloride, USP a histamine (H1) receptor antagonist, is a white to slight yellowish crystalline powder. It has the following structural formula:
Boxed warning
None in the current label
Causality screen of the 40 strongest signals
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.
- 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). 1,115 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 |
|---|---|---|---|---|---|---|
| Narcotic bowel syndrome | 16 | 123.1 73.4–206.5ROR 123.2 · calibrated p 1e-7 ✓ | 97.8 EB05 63.9 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious n=16 | not reported in cached trials |
| Echolalia | 19 | 67.9 42.7–108.0ROR 68.0 · calibrated p 6e-6 ✓ | 60.2 EB05 40.7 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious n=19 | not reported in cached trials |
| Chronic kidney disease-mineral and bone disorder | 46 | 48.1 35.8–64.6ROR 48.2 · calibrated p 3e-5 ✓ | 45.2 EB05 35.3 · IC025 +4.5 3/3 methods agree | Not in label — unassessed | serious n=46 | not reported in cached trials |
| Hyperparathyroidism secondary | 102 | 45.2 37.1–55.1ROR 45.4 · calibrated p 3e-5 ✓ | 43.1 EB05 36.5 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=102 | not reported in cached trials |
| Nephrogenic anaemia | 183 | 43.8 37.8–50.8ROR 44.3 · calibrated p 3e-5 ✓ | 42.0 EB05 37.1 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious n=183 | not reported in cached trials |
| Salivary gland calculus | 14 | 42.7 25.0–72.9ROR 42.7 · calibrated p 1e-4 ✓ | 39.1 EB05 24.7 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=14 | not reported in cached trials |
| Rebound acid hypersecretion | 97 | 35.1 28.7–43.0ROR 35.3 · calibrated p 1e-4 ✓ | 33.8 EB05 28.6 · IC025 +4.5 3/3 methods agree | Not in label — unassessed | serious n=97 | not reported in cached trials |
| Infantile apnoea | 15 | 20.2 12.1–33.7ROR 20.2 · calibrated p 0.003 ✓ | 19.2 EB05 12.0 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious n=15 | not reported in cached trials |
| Vertigo positional | 31 | 19.4 13.6–27.7ROR 19.5 · calibrated p 0.003 ✓ | 18.9 EB05 13.9 · IC025 +3.3 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=26 | not reported in cached trials |
| Inner ear disorder | 16 | 16.4 10.0–26.9ROR 16.4 · calibrated p 0.008 ✓ | 15.5 EB05 9.6 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | – | not reported in cached trials |
| End stage renal disease | 250 | 14.8 13.1–16.8ROR 15.0 · calibrated p 0.007 ✓ | 14.6 EB05 13.1 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious PRR 13.7 | not reported in cached trials |
| Sialoadenitis | 17 | 13.6 8.5–22.0ROR 13.7 · calibrated p 0.015 ✓ | 12.6 EB05 7.7 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious n=16 | not reported in cached trials |
| Vertigo (spinning dizziness) | 737 | 13.2 12.3–14.1ROR 13.6 · calibrated p 0.010 ✓ | 13.0 EB05 12.2 · IC025 +3.6 3/3 methods agree | Likely indication confounding term in indications | serious PRR 11.0 | not reported in cached trials |
| Sick sinus syndrome | 14 | 13.1 7.7–22.2ROR 13.1 · calibrated p 0.018 ✓ | 11.7 EB05 6.7 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious n=14 | not reported in cached trials |
| Motion sickness | 23 | 13.1 8.7–19.7ROR 13.1 · calibrated p 0.016 ✓ | 12.3 EB05 8.2 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | – | not reported in cached trials |
| Chronic kidney disease | 906 | 12.9 12.1–13.7ROR 13.4 · calibrated p 0.011 ✓ | 12.7 EB05 12.0 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious PRR 12.1 | not reported in cached trials |
| Infusion site discharge | 18 | 11.4 7.2–18.2ROR 11.5 · calibrated p 0.027 ✓ | 10.3 EB05 6.4 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious n=13 | not reported in cached trials |
| Cataplexy | 15 | 11.4 6.9–19.0ROR 11.4 · calibrated p 0.029 ✓ | 10.0 EB05 5.9 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious n=13 | not reported in cached trials |
| Essential hypertension | 27 | 11.3 7.8–16.6ROR 11.3 · calibrated p 0.025 ✓ | 10.6 EB05 7.3 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious n=23 | not reported in cached trials |
| Intentional misuse | 19 | 10.7 6.8–16.7ROR 10.7 · calibrated p 0.033 ✓ | 9.5 EB05 6.1 · IC025 +2.3 3/3 methods agree | Reporting / coding artifact | serious n=19 | not reported in cached trials |
| Colonic polyp | 16 | 10.4 6.3–17.0ROR 10.4 · calibrated p 0.038 ✓ | 9.0 EB05 5.5 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious n=16 | not reported in cached trials |
| Neck injury | 28 | 10.3 7.1–15.0ROR 10.3 · calibrated p 0.034 ✓ | 9.5 EB05 6.7 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious n=25 | not reported in cached trials |
| Economic problem | 140 | 9.9 8.4–11.6ROR 9.9 · calibrated p 0.034 ✓ | 9.6 EB05 8.3 · IC025 +3.0 3/3 methods agree | Reporting / coding artifact | serious PRR 9.9 · 73% consumer | not reported in cached trials |
| Labyrinthitis | 23 | 9.8 6.5–14.8ROR 9.8 · calibrated p 0.042 ✓ | 8.8 EB05 6.0 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious n=19 | not reported in cached trials |
| Pre-existing condition improved | 55 | 9.5 7.3–12.3ROR 9.5 · calibrated p 0.042 ✓ | 9.0 EB05 7.1 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious n=32 | not reported in cached trials |
| Acute sinusitis | 15 | 9.5 5.7–15.7ROR 9.5 · calibrated p 0.052 | 8.0 EB05 4.9 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious n=14 | not reported in cached trials |
| Infusion site haemorrhage | 28 | 9.4 6.5–13.6ROR 9.4 · calibrated p 0.047 ✓ | 8.6 EB05 6.0 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious n=14 · ♀ 100% (drug 74%) · 100% consumer | not reported in cached trials |
| Middle ear effusion | 18 | 8.9 5.6–14.1ROR 8.9 · calibrated p 0.060 | 7.7 EB05 5.0 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious n=14 | not reported in cached trials |
| Excoriation | 21 | 8.8 5.8–13.6ROR 8.9 · calibrated p 0.059 | 7.8 EB05 5.2 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious n=20 | not reported in cached trials |
| Rhinitis allergic | 35 | 8.5 6.1–11.9ROR 8.6 · calibrated p 0.060 | 7.9 EB05 5.8 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious n=32 | not reported in cached trials |
| Infusion site pruritus | 24 | 8.3 5.6–12.5ROR 8.4 · calibrated p 0.068 | 7.4 EB05 5.2 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious n=17 · ♀ 100% (drug 74%) | not reported in cached trials |
| Diabetic neuropathy | 38 | 8.3 6.0–11.4ROR 8.3 · calibrated p 0.066 | 7.7 EB05 5.8 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious n=38 | not reported in cached trials |
| Gastrointestinal hypomotility | 17 | 8.3 5.1–13.3ROR 8.3 · calibrated p 0.075 | 7.1 EB05 4.5 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious n=15 | not reported in cached trials |
| Intervertebral disc degeneration | 70 | 8.2 6.4–10.3ROR 8.2 · calibrated p 0.066 | 7.8 EB05 6.3 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 7.7 | not reported in cached trials |
| Lumbar spinal stenosis | 22 | 8.1 5.3–12.4ROR 8.1 · calibrated p 0.074 | 7.2 EB05 4.9 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious n=20 | not reported in cached trials |
| Femoral neck fracture | 38 | 8.0 5.8–11.0ROR 8.0 · calibrated p 0.072 | 7.4 EB05 5.6 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious n=38 · 100% clinician | not reported in cached trials |
| Ear disorder | 34 | 8.0 5.7–11.2ROR 8.0 · calibrated p 0.074 | 7.4 EB05 5.4 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious n=28 | not reported in cached trials |
| Bronchitis chronic | 18 | 7.9 5.0–12.6ROR 7.9 · calibrated p 0.083 | 6.8 EB05 4.5 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious n=17 | not reported in cached trials |
| Hyperlipidaemia | 85 | 7.7 6.2–9.5ROR 7.7 · calibrated p 0.077 | 7.4 EB05 6.1 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 6.9 | not reported in cached trials |
| Diverticulum | 50 | 7.5 5.7–9.9ROR 7.5 · calibrated p 0.085 | 7.1 EB05 5.5 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious n=47 | 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 Meclizine 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).
- NCT01443858 — Meclizine as a Potential Smoking Cessation Treatment (N=146, PHASE2; 16 AE terms posted; arms: Control; 25mg Meclizine; 50mg Meclizine)
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 |
|---|---|---|---|---|---|---|
| Dizziness | 1,951 | 4.2 4.1–4.4ROR 4.6 · calibrated p 0.284 | 4.2 EB05 4.1 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 4.2 | not reported in cached trials |
| Nausea | 1,743 | 2.4 2.3–2.5ROR 2.5 · calibrated p 0.805 | 2.4 EB05 2.3 · IC025 +1.2 3/3 methods agree | Not in label — unassessed | serious PRR 2.6 | NCT01443858: 2/25 (8.0%) on Meclizine; 6/19 (31.6%) control |
| Fatigue (tiredness) | 1,650 | 2.3 2.2–2.4ROR 2.4 · calibrated p 0.853 | 2.3 EB05 2.2 · IC025 +1.1 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.4 | NCT01443858: 5/25 (20.0%) on Meclizine; 2/19 (10.5%) control |
| Headache | 1,273 | 2.2 2.1–2.3ROR 2.3 · calibrated p 0.915 | 2.2 EB05 2.1 · IC025 +1.0 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.4 | NCT01443858: 2/25 (8.0%) on Meclizine; 3/19 (15.8%) control |
| Diarrhoea (diarrhea) | 1,239 | 2.1 2.0–2.2ROR 2.1 · calibrated p 0.977 | 2.1 EB05 2.0 · IC025 +1.0 | Not in label — unassessed | serious PRR 2.0 | NCT01443858: 1/25 (4.0%) on Meclizine; 2/19 (10.5%) control |
| Fall | 1,195 | 3.9 3.7–4.1ROR 4.1 · calibrated p 0.365 | 3.9 EB05 3.7 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 3.6 | not reported in cached trials |
| Pain | 1,171 | 2.1 1.9–2.2ROR 2.1 · calibrated p 0.993 | 2.0 EB05 2.0 · IC025 +0.9 | Not in label — unassessed | serious PRR 2.2 | not reported in cached trials |
| Dyspnoea (shortness of breath) | 1,003 | 1.9 1.8–2.0ROR 2.0 · calibrated p 0.923 | 1.9 EB05 1.8 · IC025 +0.8 | Not in label — unassessed | serious PRR 1.8 | not reported in cached trials |
| Drug ineffective (drug did not work) | 978 | 0.8 0.8–0.9ROR 0.8 · calibrated p 0.178 | 0.8 EB05 0.8 · IC025 -0.4 PRR-only: not supported by EBGM or IC | Reporting / coding artifact | serious PRR 0.8 | not reported in cached trials |
| Asthenia (weakness) | 966 | 2.8 2.6–2.9ROR 2.9 · calibrated p 0.673 | 2.8 EB05 2.6 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 2.7 | not reported in cached trials |
| Vomiting | 910 | 2.1 2.0–2.2ROR 2.1 · calibrated p 0.979 | 2.1 EB05 2.0 · IC025 +1.0 | Labeled adverse reaction exact term | serious PRR 2.0 | not reported in cached trials |
| Chronic kidney disease | 906 | 12.9 12.1–13.7ROR 13.4 · calibrated p 0.011 ✓ | 12.7 EB05 12.0 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious PRR 12.1 | not reported in cached trials |
| Vertigo (spinning dizziness) | 737 | 13.2 12.3–14.1ROR 13.6 · calibrated p 0.010 ✓ | 13.0 EB05 12.2 · IC025 +3.6 3/3 methods agree | Likely indication confounding term in indications | serious PRR 11.0 | not reported in cached trials |
| Anxiety | 726 | 2.7 2.6–2.9ROR 2.8 · calibrated p 0.691 | 2.7 EB05 2.6 · IC025 +1.3 3/3 methods agree | Not in label — unassessed | serious PRR 3.1 | not reported in cached trials |
| Off label use (used outside approved label) | 723 | 0.9 0.8–1.0ROR 0.9 · calibrated p 0.239 | 0.9 EB05 0.8 · IC025 -0.3 PRR-only: not supported by EBGM or IC | Reporting / coding artifact | serious PRR 0.9 | 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.
- Chronic kidney disease-mineral and bone disorder — n=46, PRR 48.1
- Hyperparathyroidism secondary — n=102, PRR 45.2
- Nephrogenic anaemia — n=183, PRR 43.8
- Rebound acid hypersecretion — n=97, PRR 35.1
- End stage renal disease — n=250, PRR 14.8
- Motion sickness — n=23, PRR 13.1
- Chronic kidney disease — n=906, PRR 12.9
- Essential hypertension — n=27, PRR 11.3
- Neck injury — n=28, PRR 10.3
- Labyrinthitis — n=23, PRR 9.8
✓ A hand-written Bradford Hill causality assessment exists for this drug: Oxycodone Hydrochloride ↔ Drug Dependence.
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 Meclizine?
In FDA FAERS, the most frequently co-reported reaction terms for Meclizine are dizziness, nausea, fatigue, headache, diarrhoea, fall. 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 Meclizine have an FDA boxed warning?
No. The FDA label retrieved for Meclizine has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Meclizine 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 1079db3f-d8ad-4c25-aa91-8ac8054ee4f2, effective 20260608; matched on
openfda.generic_name.exact:"MECLIZINE") - 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, 1,155 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
MECLIZINE, 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.