Methocarbamol Tablets side effects: what 16,630 FDA adverse event reports show

Methocarbamol Tablets · 1,144 reaction terms · 74,101 drug–reaction co-reports · data 2026-09-14

Drug class

Muscle Relaxant

FDA label (Established Pharmacologic Class) · compare the class

Who reports

16,630 reports · 63% serious · 1,398 with death outcome · 68% female

openFDA FAERS counts, all years, deduplication not applied

Used for

The injectable form of methocarbamol is indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions. The mode of action of this drug has not been clearly identified, but may be related to its sedative properties. Methocarbamol does not directly relax tense skeletal muscles in man.

FDA label, Indications and Usage

What it is

DESCRIPTION Methocarbamol Injection, USP a carbamate derivative of guaifenesin, is a central nervous system (CNS) depressant with sedative and musculoskeletal relaxant properties. It is a sterile, pyrogen-free solution intended for intramuscular or intravenous administration.

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

Reporting / coding artifact 7Lab value / disease marker 1Not in label — unassessed 32

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.
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. 1,104 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
Amyloid arthropathy	28	966.0 589.7–1,582.6ROR 967.6 · χ² 14,645 / p <1e-300	396.2 EB05 287.7 · IC025 +5.1 3/3 methods agree	Not in label — unassessed	serious n=28 · ♀ 100% (drug 68%) · 100% clinician	not reported in cached trials
Product administration issue	14	276.0 154.7–492.4ROR 276.2 · χ² 2,918 / p <1e-300	173.1 EB05 109.6 · IC025 +3.8 3/3 methods agree	Reporting / coding artifact	serious n=14	not reported in cached trials
Child abuse	41	247.2 176.9–345.5ROR 247.8 · χ² 8,180 / p <1e-300	188.3 EB05 144.7 · IC025 +5.4 3/3 methods agree	Reporting / coding artifact	serious n=41 · ♀ 0% (drug 68%) · 100% clinician	not reported in cached trials
Epidural lipomatosis	42	172.7 125.1–238.5ROR 173.2 · χ² 6,146 / p <1e-300	142.1 EB05 109.5 · IC025 +5.3 3/3 methods agree	Not in label — unassessed	serious n=42 · ♀ 0% (drug 68%) · 100% clinician	not reported in cached trials
Victim of child abuse	27	154.5 103.6–230.5ROR 154.8 · χ² 3,528 / p <1e-300	125.5 EB05 90.6 · IC025 +4.7 3/3 methods agree	Reporting / coding artifact	serious n=27 · ♀ 0% (drug 68%) · 100% clinician	not reported in cached trials
Necrosis ischaemic	26	74.9 50.4–111.3ROR 75.0 · χ² 1,719 / p <1e-300	67.4 EB05 48.3 · IC025 +4.3 3/3 methods agree	Not in label — unassessed	serious n=26 · ♀ 100% (drug 68%) · 100% clinician	not reported in cached trials
Multiple drug therapy	39	74.5 54.0–102.9ROR 74.7 · χ² 2,600 / p <1e-300	68.1 EB05 52.0 · IC025 +4.7 3/3 methods agree	Reporting / coding artifact	serious n=38 · ♀ 100% (drug 68%) · 100% clinician	not reported in cached trials
Chronic kidney disease-mineral and bone disorder	34	41.1 29.2–57.8ROR 41.2 · χ² 1,248 / p 9e-274	39.0 EB05 29.2 · IC025 +4.1 3/3 methods agree	Not in label — unassessed	serious n=34	not reported in cached trials
Pneumonia streptococcal	27	31.7 21.7–46.5ROR 31.8 · χ² 754 / p 3e-166	30.4 EB05 21.9 · IC025 +3.7 3/3 methods agree	Not in label — unassessed	serious n=27 · ♀ 100% (drug 68%) · 100% clinician	not reported in cached trials
Device maintenance issue	13	29.7 17.1–51.4ROR 29.7 · χ² 324 / p 8e-73	27.9 EB05 17.3 · IC025 +2.9 3/3 methods agree	Reporting / coding artifact	–	not reported in cached trials
Acquired haemophilia	21	27.3 17.7–42.1ROR 27.4 · χ² 496 / p 4e-110	26.2 EB05 18.1 · IC025 +3.3 3/3 methods agree	Not in label — unassessed	serious n=21	not reported in cached trials
Rebound acid hypersecretion	64	26.8 21.0–34.3ROR 26.9 · χ² 1,533 / p <1e-300	26.1 EB05 21.2 · IC025 +4.0 3/3 methods agree	Not in label — unassessed	serious n=64	not reported in cached trials
Beta haemolytic streptococcal infection	26	26.6 18.1–39.2ROR 26.7 · χ² 603 / p 2e-133	25.7 EB05 18.4 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious n=26 · ♀ 100% (drug 68%) · 100% clinician	not reported in cached trials
Hyperparathyroidism secondary	51	25.9 19.6–34.1ROR 26.0 · χ² 1,171 / p 7e-257	25.2 EB05 19.9 · IC025 +3.9 3/3 methods agree	Not in label — unassessed	serious n=51 · ♀ 41% (drug 68%)	not reported in cached trials
Nephrogenic anaemia	94	25.8 21.1–31.7ROR 26.0 · χ² 2,174 / p <1e-300	25.2 EB05 21.2 · IC025 +4.1 3/3 methods agree	Not in label — unassessed	serious n=94	not reported in cached trials
Bone demineralisation	21	25.4 16.5–39.1ROR 25.4 · χ² 459 / p 5e-102	24.4 EB05 16.8 · IC025 +3.3 3/3 methods agree	Not in label — unassessed	serious n=18	not reported in cached trials
Distributive shock	43	25.0 18.5–33.8ROR 25.0 · χ² 947 / p 3e-208	24.3 EB05 18.8 · IC025 +3.8 3/3 methods agree	Not in label — unassessed	serious n=43 · ♀ 100% (drug 68%) · 100% clinician	not reported in cached trials
Juvenile idiopathic arthritis	42	22.0 16.2–29.8ROR 22.0 · χ² 805 / p 2e-177	21.4 EB05 16.5 · IC025 +3.6 3/3 methods agree	Not in label — unassessed	serious n=42 · ♀ 0% (drug 68%) · 100% clinician	not reported in cached trials
Drug clearance decreased	15	15.2 9.1–25.2ROR 15.2 · χ² 182 / p 7e-42	14.1 EB05 8.4 · IC025 +2.5 3/3 methods agree	Lab value / disease marker	serious n=15	not reported in cached trials
Product administration interrupted	90	14.9 12.1–18.4ROR 15.0 · χ² 1,144 / p 5e-251	14.7 EB05 12.3 · IC025 +3.4 3/3 methods agree	Reporting / coding artifact	serious n=82	not reported in cached trials
Narcolepsy	22	14.9 9.8–22.6ROR 14.9 · χ² 267 / p 2e-60	14.2 EB05 9.5 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious n=21	not reported in cached trials
Suspected suicide	55	14.7 11.3–19.2ROR 14.7 · χ² 680 / p 3e-150	14.4 EB05 11.4 · IC025 +3.2 3/3 methods agree	Not in label — unassessed	serious n=55 · 100% clinician	not reported in cached trials
Infusion site discharge	19	14.1 9.0–22.2ROR 14.2 · χ² 217 / p 3e-49	13.3 EB05 8.5 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious n=14	not reported in cached trials
Spinal cord injury	19	13.8 8.8–21.7ROR 13.8 · χ² 211 / p 4e-48	13.0 EB05 8.3 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious n=19	not reported in cached trials
Pulmonary pain	30	13.3 9.3–19.0ROR 13.3 · χ² 325 / p 5e-73	12.7 EB05 9.1 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious n=29 · ♀ 100% (drug 68%) · 100% clinician	not reported in cached trials
Lumbar radiculopathy	12	13.1 7.4–23.1ROR 13.1 · χ² 121 / p 2e-28	11.4 EB05 6.2 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious n=11	not reported in cached trials
Respiratory depression	124	12.9 10.8–15.3ROR 12.9 · χ² 1,331 / p 9e-292	12.7 EB05 10.9 · IC025 +3.3 3/3 methods agree	Not in label — unassessed	serious PRR 12.1 · ♀ 11% (drug 68%)	not reported in cached trials
Neck surgery	23	12.7 8.4–19.2ROR 12.7 · χ² 235 / p 3e-53	11.9 EB05 8.0 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious n=23	not reported in cached trials
Pre-existing condition improved	63	12.7 9.9–16.3ROR 12.7 · χ² 660 / p 6e-146	12.4 EB05 9.9 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious n=36	not reported in cached trials
Cervical spinal stenosis	17	12.5 7.8–20.1ROR 12.5 · χ² 167 / p 2e-38	11.4 EB05 7.0 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious n=17	not reported in cached trials
Infusion site irritation	12	12.3 6.9–21.7ROR 12.3 · χ² 112 / p 2e-26	10.5 EB05 5.7 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	–	NCT02665286: 4/80 (5.0%) on Methocarbamol; 1/76 (1.3%) control
Exercise tolerance decreased	53	11.8 9.0–15.4ROR 11.8 · χ² 508 / p 8e-113	11.4 EB05 8.9 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious n=50 · ♀ 100% (drug 68%)	not reported in cached trials
Postural orthostatic tachycardia syndrome	12	11.6 6.6–20.5ROR 11.6 · χ² 105 / p 6e-25	9.8 EB05 5.4 · IC025 +2.0 3/3 methods agree	Not in label — unassessed	serious n=11	not reported in cached trials
Spinal operation	110	11.5 9.6–13.9ROR 11.6 · χ² 1,040 / p 2e-228	11.3 EB05 9.6 · IC025 +3.1 3/3 methods agree	Reporting / coding artifact	serious PRR 10.9	not reported in cached trials
Blood pressure inadequately controlled	55	11.5 8.8–15.0ROR 11.6 · χ² 513 / p 6e-114	11.1 EB05 8.8 · IC025 +2.9 3/3 methods agree	Not in label — unassessed	serious n=55 · ♀ 100% (drug 68%)	not reported in cached trials
End stage renal disease	167	11.5 9.9–13.4ROR 11.6 · χ² 1,580 / p <1e-300	11.3 EB05 9.9 · IC025 +3.2 3/3 methods agree	Not in label — unassessed	serious PRR 10.5	not reported in cached trials
Infusion site haemorrhage	28	11.0 7.6–15.9ROR 11.0 · χ² 242 / p 9e-55	10.2 EB05 7.2 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious n=19 · 82% consumer	not reported in cached trials
Costochondritis	14	10.9 6.4–18.4ROR 10.9 · χ² 115 / p 4e-27	9.3 EB05 5.5 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious n=13	not reported in cached trials
Spinal fusion surgery	34	10.7 7.7–15.1ROR 10.8 · χ² 288 / p 6e-65	10.1 EB05 7.4 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious n=33	not reported in cached trials
Chronic kidney disease	648	10.7 9.9–11.6ROR 11.1 · χ² 5,681 / p <1e-300	10.6 EB05 10.0 · IC025 +3.3 3/3 methods agree	Not in label — unassessed	serious PRR 9.9	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 Methocarbamol 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 (1 of 40 signal terms matched).

NCT02665286 — Orphenadrine and Methocarbamol for LBP (N=240, PHASE4; 4 AE terms posted; arms: Placebo; Orphenadrine; Methocarbamol)

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)	1,222	2.0 1.9–2.1ROR 2.1 · χ² 616 / p 2e-136	2.0 EB05 1.9 · IC025 +0.9	Not in label — unassessed	serious PRR 2.0	not reported in cached trials
Pain	1,210	2.5 2.3–2.6ROR 2.6 · χ² 1,097 / p 6e-241	2.5 EB05 2.4 · IC025 +1.2 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 2.4	not reported in cached trials
Nausea	1,157	1.8 1.7–2.0ROR 1.9 · χ² 467 / p 8e-104	1.8 EB05 1.8 · IC025 +0.8	Labeled adverse reaction exact term	serious PRR 2.0	NCT02665286: 3/80 (3.8%) on Methocarbamol; 1/76 (1.3%) control
Drug ineffective (drug did not work)	1,095	1.0 1.0–1.1ROR 1.1 · χ² 2 / p 0.058	1.0 EB05 1.0 · IC025 -0.0 PRR-only: not supported by EBGM or IC	Reporting / coding artifact	serious PRR 1.3	not reported in cached trials
Headache	935	1.9 1.8–2.0ROR 1.9 · χ² 397 / p 1e-88	1.9 EB05 1.8 · IC025 +0.8	Labeled adverse reaction exact term	serious PRR 2.2	not reported in cached trials
Diarrhoea (diarrhea)	839	1.6 1.5–1.8ROR 1.7 · χ² 217 / p 2e-49	1.6 EB05 1.6 · IC025 +0.6	Not in label — unassessed	serious PRR 1.6	not reported in cached trials
Fall	796	3.0 2.8–3.2ROR 3.1 · χ² 1,089 / p 5e-239	3.0 EB05 2.8 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 2.8	not reported in cached trials
Off label use (used outside approved label)	790	1.1 1.1–1.2ROR 1.2 · χ² 15 / p 5e-5	1.1 EB05 1.1 · IC025 +0.1	Reporting / coding artifact	serious PRR 1.3	not reported in cached trials
Dyspnoea (shortness of breath)	759	1.7 1.6–1.8ROR 1.7 · χ² 219 / p 6e-50	1.7 EB05 1.6 · IC025 +0.6	Not in label — unassessed	serious PRR 1.6	not reported in cached trials
Arthralgia (joint pain)	739	2.2 2.1–2.4ROR 2.3 · χ² 521 / p 2e-115	2.2 EB05 2.1 · IC025 +1.0 3/3 methods agree	Not in label — unassessed	serious PRR 2.4	not reported in cached trials
Dizziness	682	1.7 1.6–1.9ROR 1.8 · χ² 213 / p 2e-48	1.7 EB05 1.6 · IC025 +0.7	Labeled adverse reaction exact term	serious PRR 1.9	not reported in cached trials
Chronic kidney disease	648	10.7 9.9–11.6ROR 11.1 · χ² 5,681 / p <1e-300	10.6 EB05 10.0 · IC025 +3.3 3/3 methods agree	Not in label — unassessed	serious PRR 9.9	not reported in cached trials
Back pain	634	3.4 3.2–3.7ROR 3.5 · χ² 1,105 / p 1e-242	3.4 EB05 3.2 · IC025 +1.6 3/3 methods agree	Not in label — unassessed	serious PRR 3.9	not reported in cached trials
Anxiety	628	2.8 2.6–3.0ROR 2.8 · χ² 720 / p 5e-159	2.8 EB05 2.6 · IC025 +1.3 3/3 methods agree	Not in label — unassessed	serious PRR 3.1	not reported in cached trials
Vomiting	599	1.6 1.5–1.7ROR 1.6 · χ² 141 / p 9e-33	1.6 EB05 1.5 · IC025 +0.6	Labeled adverse reaction exact term	serious PRR 1.6	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.

Amyloid arthropathy — n=28, PRR 966.0
Epidural lipomatosis — n=42, PRR 172.7
Necrosis ischaemic — n=26, PRR 74.9
Chronic kidney disease-mineral and bone disorder — n=34, PRR 41.1
Pneumonia streptococcal — n=27, PRR 31.7
Acquired haemophilia — n=21, PRR 27.3
Rebound acid hypersecretion — n=64, PRR 26.8
Beta haemolytic streptococcal infection — n=26, PRR 26.6
Hyperparathyroidism secondary — n=51, PRR 25.9
Nephrogenic anaemia — n=94, PRR 25.8

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 Methocarbamol?

In FDA FAERS, the most frequently co-reported reaction terms for Methocarbamol are fatigue, pain, nausea, 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 Methocarbamol have an FDA boxed warning?

No. The FDA label retrieved for Methocarbamol has no boxed warning; see the label's Warnings and Precautions for the recognised risks.

Do FAERS signals prove that Methocarbamol 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 01e7e2c7-49eb-4afb-a496-f2bd901622e9, effective 20250929; matched on openfda.generic_name.exact:"METHOCARBAMOL")
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, 1,144 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 METHOCARBAMOL, 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.