Amantadine side effects: what 15,376 FDA adverse event reports show
Drug class
Lower incidence of these side effects than
Who reports
15,376 reports · 60% serious · 1,632 with death outcome · 56% female
Used for
Amantadine hydrochloride tablets are indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. Amantadine hydrochloride tablets are also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.
What it is
DESCRIPTION Amantadine hydrochloride, USP is designated generically as amantadine hydrochloride and chemically as 1-adamantanamine hydrochloride. Amantadine hydrochloride, USP is a stable white or practically white crystalline powder, freely soluble in water, soluble in alcohol and in chloroform.
Boxed warning
None in the current label
Causality screen of the 40 strongest signals
What the badges mean
- 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.
- 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. 1,082 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 |
|---|---|---|---|---|---|---|
| Dyskinesia hyperpyrexia syndrome | 29 | 2,166.0 1,203.2–3,899.3ROR 2,170.1 · χ² 23,212 / p <1e-300 | 535.3 EB05 390.9 · IC025 +5.2 3/3 methods agree | Not in label — unassessed | serious n=29 · ♀ 100% (drug 56%) · 100% clinician | not reported in cached trials |
| Parkinsonism hyperpyrexia syndrome | 43 | 425.1 301.8–598.7ROR 426.3 · χ² 13,502 / p <1e-300 | 282.6 EB05 218.6 · IC025 +5.6 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=43 · 100% clinician | not reported in cached trials |
| Dopamine dysregulation syndrome | 47 | 160.0 118.3–216.4ROR 160.5 · χ² 6,494 / p <1e-300 | 135.3 EB05 105.8 · IC025 +5.4 3/3 methods agree | Not in label — unassessed | serious n=44 · ♀ 29% (drug 56%) · 100% clinician | not reported in cached trials |
| Deep brain stimulation | 61 | 159.9 122.7–208.4ROR 160.5 · χ² 8,465 / p <1e-300 | 136.9 EB05 110.4 · IC025 +5.6 3/3 methods agree | Not in label — unassessed | serious n=58 · 90% consumer | not reported in cached trials |
| Freezing phenomenon | 270 | 110.7 97.9–125.2ROR 112.6 · χ² 27,015 / p <1e-300 | 101.6 EB05 91.8 · IC025 +6.2 3/3 methods agree | Not in label — unassessed | serious n=184 | not reported in cached trials |
| Catheter site nodule | 11 | 102.0 55.3–188.2ROR 102.1 · χ² 931 / p 1e-204 | 81.9 EB05 48.8 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=9 | not reported in cached trials |
| Rapid eye movement sleep behaviour disorder | 25 | 91.1 60.8–136.5ROR 91.2 · χ² 2,003 / p <1e-300 | 80.3 EB05 57.2 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious n=21 | not reported in cached trials |
| Spinal cord haematoma | 13 | 88.7 50.6–155.5ROR 88.8 · χ² 977 / p 9e-215 | 74.5 EB05 46.3 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=13 | not reported in cached trials |
| On and off phenomenon | 307 | 84.4 75.3–94.6ROR 86.1 · χ² 23,735 / p <1e-300 | 79.1 EB05 71.9 · IC025 +6.0 3/3 methods agree | Not in label — unassessed | serious n=258 | not reported in cached trials |
| Stoma site odour | 12 | 76.8 42.9–137.4ROR 76.9 · χ² 779 / p 9e-172 | 65.5 EB05 39.9 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=11 | not reported in cached trials |
| Stoma site infection | 59 | 65.2 50.2–84.6ROR 65.4 · χ² 3,495 / p <1e-300 | 61.0 EB05 49.1 · IC025 +4.9 3/3 methods agree | Not in label — unassessed | serious n=49 · 75% consumer | not reported in cached trials |
| Stoma site erythema | 83 | 63.3 50.8–78.8ROR 63.6 · χ² 4,801 / p <1e-300 | 59.7 EB05 49.7 · IC025 +5.1 3/3 methods agree | Not in label — unassessed | serious n=73 | not reported in cached trials |
| Stoma site hypergranulation | 28 | 63.2 43.3–92.2ROR 63.3 · χ² 1,577 / p <1e-300 | 58.1 EB05 42.2 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious n=26 | not reported in cached trials |
| Somatic delusion | 11 | 62.9 34.4–115.2ROR 63.0 · χ² 583 / p 5e-129 | 54.8 EB05 32.6 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Stoma site pain | 58 | 56.3 43.3–73.1ROR 56.5 · χ² 2,969 / p <1e-300 | 53.1 EB05 42.6 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=50 | not reported in cached trials |
| Saliva discolouration | 13 | 55.8 32.1–97.2ROR 55.9 · χ² 621 / p 3e-137 | 50.0 EB05 31.1 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | – | not reported in cached trials |
| Stoma site discharge | 105 | 54.3 44.7–65.9ROR 54.6 · χ² 5,227 / p <1e-300 | 51.7 EB05 44.0 · IC025 +5.1 3/3 methods agree | Not in label — unassessed | serious n=88 | not reported in cached trials |
| Hyperkinesia | 79 | 53.5 42.8–67.0ROR 53.8 · χ² 3,865 / p <1e-300 | 50.9 EB05 42.2 · IC025 +4.9 3/3 methods agree | Labeled adverse reaction exact term | serious n=76 · ♀ 27% (drug 56%) | not reported in cached trials |
| Device colour issue | 14 | 49.4 29.0–84.2ROR 49.4 · χ² 595 / p 1e-131 | 45.0 EB05 28.5 · IC025 +3.3 3/3 methods agree | Reporting / coding artifact | serious n=9 | not reported in cached trials |
| Duplicate therapy error | 11 | 48.6 26.7–88.8ROR 48.7 · χ² 450 / p 3e-100 | 43.7 EB05 26.0 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | – | not reported in cached trials |
| Stoma site reaction | 23 | 47.9 31.6–72.5ROR 47.9 · χ² 974 / p 3e-214 | 44.7 EB05 31.3 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious n=21 · ♀ 30% (drug 56%) | not reported in cached trials |
| Stoma site extravasation | 13 | 46.9 27.0–81.4ROR 46.9 · χ² 520 / p 2e-115 | 42.7 EB05 26.5 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=12 | not reported in cached trials |
| Impulse-control disorder | 65 | 44.4 34.7–56.8ROR 44.6 · χ² 2,628 / p <1e-300 | 42.5 EB05 34.5 · IC025 +4.6 3/3 methods agree | Not in label — unassessed | serious n=57 | not reported in cached trials |
| Reduced facial expression | 31 | 43.5 30.4–62.2ROR 43.6 · χ² 1,206 / p 1e-264 | 41.2 EB05 30.4 · IC025 +4.1 3/3 methods agree | Not in label — unassessed | serious n=28 · ♀ 29% (drug 56%) | not reported in cached trials |
| Parkinsonian gait | 19 | 42.9 27.2–67.8ROR 43.0 · χ² 714 / p 1e-157 | 40.1 EB05 27.1 · IC025 +3.6 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=17 | not reported in cached trials |
| Morphoea | 13 | 38.2 22.0–66.4ROR 38.3 · χ² 423 / p 3e-94 | 35.5 EB05 22.0 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious n=13 | not reported in cached trials |
| Dyskinesia (involuntary movements) | 1,086 | 37.5 35.4–39.7ROR 40.3 · χ² 37,566 / p <1e-300 | 36.5 EB05 34.7 · IC025 +5.1 3/3 methods agree | Not in label — unassessed | serious PRR 28.9 | not reported in cached trials |
| Resting tremor | 17 | 36.6 22.6–59.3ROR 36.7 · χ² 539 / p 1e-119 | 34.4 EB05 22.8 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=17 | not reported in cached trials |
| Stoma complication | 25 | 34.2 23.0–50.9ROR 34.3 · χ² 754 / p 2e-166 | 32.7 EB05 23.3 · IC025 +3.7 3/3 methods agree | Reporting / coding artifact | serious n=21 · 100% consumer | not reported in cached trials |
| Livedo reticularis | 50 | 33.5 25.3–44.3ROR 33.6 · χ² 1,505 / p <1e-300 | 32.3 EB05 25.5 · IC025 +4.2 3/3 methods agree | Labeled adverse reaction exact term | serious n=23 | not reported in cached trials |
| Stoma site haemorrhage | 34 | 31.1 22.2–43.7ROR 31.2 · χ² 940 / p 9e-207 | 30.0 EB05 22.5 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious n=30 · ♀ 32% (drug 56%) · 79% consumer | not reported in cached trials |
| Sleep talking | 38 | 31.0 22.5–42.7ROR 31.1 · χ² 1,049 / p 2e-230 | 29.9 EB05 22.8 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious n=24 | not reported in cached trials |
| Bradykinesia | 128 | 30.6 25.7–36.4ROR 30.8 · χ² 3,553 / p <1e-300 | 29.8 EB05 25.7 · IC025 +4.5 3/3 methods agree | Not in label — unassessed | serious n=117 | not reported in cached trials |
| Stoma site irritation | 12 | 30.6 17.2–54.1ROR 30.6 · χ² 307 / p 5e-69 | 28.6 EB05 17.4 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Soft tissue mass | 10 | 30.1 16.1–56.4ROR 30.2 · χ² 248 / p 4e-56 | 28.0 EB05 16.1 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Hallucination, visual | 450 | 29.9 27.2–32.7ROR 30.7 · χ² 12,265 / p <1e-300 | 29.2 EB05 27.0 · IC025 +4.7 3/3 methods agree | Labeled (related wording) related wording | serious PRR 24.7 | not reported in cached trials |
| Hypersexuality | 39 | 29.6 21.6–40.6ROR 29.7 · χ² 1,026 / p 2e-225 | 28.6 EB05 21.8 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious n=33 · ♀ 25% (drug 56%) | not reported in cached trials |
| Akinesia | 42 | 28.2 20.8–38.3ROR 28.3 · χ² 1,054 / p 2e-231 | 27.4 EB05 21.1 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious n=37 · ♀ 29% (drug 56%) | not reported in cached trials |
| Stoma site inflammation | 15 | 28.0 16.8–46.8ROR 28.1 · χ² 357 / p 6e-80 | 26.6 EB05 17.1 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious n=14 | not reported in cached trials |
| Infusion site nodule | 17 | 26.2 16.2–42.3ROR 26.2 · χ² 380 / p 6e-85 | 25.1 EB05 16.5 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious n=12 | 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 Amantadine 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).
- NCT01227967 — Comparing the Efficacy, Safety, and Tolerability of Combination Antivirals (Amantadine, Ribavirin, Oseltamivir (N=881, PHASE2; 31 AE terms posted; arms: Combination Therapy; Oseltamivir Monotherapy)
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 |
|---|---|---|---|---|---|---|
| Fall | 1,773 | 7.3 7.0–7.6ROR 8.1 · χ² 9,745 / p <1e-300 | 7.3 EB05 7.0 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 6.1 | not reported in cached trials |
| Hallucination (hallucinations) | 1,308 | 24.2 23.0–25.5ROR 26.4 · χ² 28,657 / p <1e-300 | 23.8 EB05 22.7 · IC025 +4.5 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 19.7 | not reported in cached trials |
| Drug ineffective (drug did not work) | 1,259 | 1.3 1.2–1.4ROR 1.3 · χ² 95 / p 1e-22 | 1.3 EB05 1.2 · IC025 +0.3 | Reporting / coding artifact | serious PRR 1.6 | not reported in cached trials |
| Fatigue (tiredness) | 1,100 | 1.9 1.8–2.0ROR 2.0 · χ² 512 / p 1e-113 | 1.9 EB05 1.8 · IC025 +0.8 | Labeled adverse reaction exact term | serious PRR 1.8 | NCT01227967: 18/314 (5.7%) on Amantadine |
| Dyskinesia (involuntary movements) | 1,086 | 37.5 35.4–39.7ROR 40.3 · χ² 37,566 / p <1e-300 | 36.5 EB05 34.7 · IC025 +5.1 3/3 methods agree | Not in label — unassessed | serious PRR 28.9 | not reported in cached trials |
| Dizziness | 945 | 2.6 2.4–2.8ROR 2.7 · χ² 942 / p 3e-207 | 2.6 EB05 2.5 · IC025 +1.3 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.1 | NCT01227967: 23/314 (7.3%) on Amantadine |
| Gait disturbance | 899 | 6.4 6.0–6.8ROR 6.7 · χ² 4,119 / p <1e-300 | 6.4 EB05 6.0 · IC025 +2.6 3/3 methods agree | Labeled (related wording) related wording | serious PRR 5.5 | not reported in cached trials |
| Death | 872 | 1.4 1.3–1.5ROR 1.4 · χ² 95 / p 9e-23 | 1.4 EB05 1.3 · IC025 +0.4 | Outcome field, not a reaction | serious PRR 1.3 | not reported in cached trials |
| Tremor (shaking) | 799 | 6.6 6.1–7.0ROR 6.9 · χ² 3,787 / p <1e-300 | 6.5 EB05 6.2 · IC025 +2.6 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 5.4 | not reported in cached trials |
| Nausea | 680 | 1.2 1.1–1.3ROR 1.2 · χ² 18 / p 1e-5 | 1.2 EB05 1.1 · IC025 +0.1 | Labeled adverse reaction exact term | serious PRR 1.0 | NCT01227967: 1/314 (0.3%) on Amantadine (serious AE) |
| Asthenia (weakness) | 648 | 2.4 2.2–2.5ROR 2.4 · χ² 510 / p 3e-113 | 2.3 EB05 2.2 · IC025 +1.1 3/3 methods agree | Not in label — unassessed | serious PRR 2.1 | not reported in cached trials |
| Condition aggravated | 626 | 2.8 2.6–3.1ROR 2.9 · χ² 748 / p 5e-165 | 2.8 EB05 2.6 · IC025 +1.4 3/3 methods agree | Reporting / coding artifact | serious PRR 2.3 | not reported in cached trials |
| Balance disorder | 625 | 9.9 9.2–10.7ROR 10.3 · χ² 4,980 / p <1e-300 | 9.8 EB05 9.2 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious PRR 8.9 | not reported in cached trials |
| Confusional state (confusion) | 623 | 5.3 4.9–5.7ROR 5.4 · χ² 2,155 / p <1e-300 | 5.2 EB05 4.9 · IC025 +2.3 3/3 methods agree | Labeled (related wording) related wording | serious PRR 4.5 | not reported in cached trials |
| Somnolence (drowsiness) | 620 | 4.2 3.9–4.6ROR 4.3 · χ² 1,527 / p <1e-300 | 4.2 EB05 3.9 · IC025 +1.9 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 3.5 | 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.
- Dyskinesia hyperpyrexia syndrome — n=29, PRR 2,166.0
- Dopamine dysregulation syndrome — n=47, PRR 160.0
- Deep brain stimulation — n=61, PRR 159.9
- Freezing phenomenon — n=270, PRR 110.7
- Rapid eye movement sleep behaviour disorder — n=25, PRR 91.1
- On and off phenomenon — n=307, PRR 84.4
- Stoma site infection — n=59, PRR 65.2
- Stoma site erythema — n=83, PRR 63.3
- Stoma site hypergranulation — n=28, PRR 63.2
- Stoma site pain — n=58, PRR 56.3
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 Amantadine?
In FDA FAERS, the most frequently co-reported reaction terms for Amantadine are fall, hallucination, fatigue, dyskinesia, dizziness, gait disturbance. 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 Amantadine have an FDA boxed warning?
No. The FDA label retrieved for Amantadine has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Amantadine 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 2ff05131-f634-4688-86e9-9bc33a8d11c4, effective 20260123; matched on
openfda.generic_name.exact:"AMANTADINE") - 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, 1,122 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
AMANTADINE, results-bearing studies sorted by enrollment)
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.