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cyclobenzaprine

Sold as Amrix, Fexmid, Tonmya. First FDA approval 08/26/1977: 49 years on the US market.

This grade answers one narrow question: how strong is the public evidence and safety record behind this drug, and how clean is its money trail and court record? It is not a verdict on whether the drug is right for you.

B

Score breakdown (76/100)

Safety ×35%
A
Evidence ×25%
F
Regulatory ×15%
B
Money & lawsuits ×15%
A
Options ×10%
C

Safety: 90

Evidence: 40

Regulatory history: 85

Money & lawsuits: 100

Options: 70

What the FDA label says

Approved uses

Cyclobenzaprine hydrochloride extended-release capsules are indicated as an adjunct to rest and physical therapy for relief of muscle spasm associated with acute, painful musculoskeletal conditions. Improvement is manifested by relief of muscle spasm and its associated signs and symptoms, namely, pain, tenderness, and limitation of motion. Limitations of Use: Cyclobenzaprine hydrochloride extended-release capsules should be used only for short periods (up to two or three weeks) because adequate evidence of effectiveness for more prolonged use is not available and because muscle spasm associated with acute, painful musculoskeletal conditions is generally of short duration and specific therapy for longer periods is seldom warranted. Cyclobenzaprine hydrochloride extended-release capsules have not been found effective in the treatment of spasticity associated with cerebral or spinal cord disease or in children with cerebral palsy. Cyclobenzaprine hydrochloride extended-release capsules are a muscle relaxant indicated as an adjunct to rest and physical therapy for relief of muscle spasm associated with acute, painful musculoskeletal conditions. Improvement is manifested by relief of mu...

Contraindications

Hypersensitivity to any component of this product. Adverse reactions may include anaphylactic reaction, urticaria, facial and/or tongue swelling, or pruritus. Discontinue cyclobenzaprine hydrochloride extended-release capsules if a hypersensitivity reaction is suspected. Concomitant use of monoamine oxidase (MAO) inhibitors or within 14 days after their discontinuation. Hyperpyretic crisis seizures and deaths have occurred in patients receiving cyclobenzaprine (or structurally similar tricyclic antidepressants) concomitantly with MAO inhibitor drugs. During the acute recovery phase of myocardial infarction, and in patients with arrhythmias, heart block or conduction disturbances, or congestive heart failure. Hyperthyroidism. Hypersensitivity to any component of this product ( 4 ) Concomitant use of monoamine oxidase (MAO) inhibitors or within 14 days after their discontinuation ( 4 ) During acute recovery phase of myocardial infarction, and in patients with arrhythmias, heart block or conduction disturbances, or congestive heart failure ( 4 ) Hyperthyroidism ( 4 )

Warnings and precautions

Serotonin syndrome has been reported with cyclobenzaprine when used in combination with other serotonergic drugs ( 5.1 ) Cyclobenzaprine is structurally related to tricyclic antidepressants which have been reported to produce adverse cardiovascular effects or CNS depressant effects ( 5.2 ) Use in the elderly is not recommended ( 5.3 ) Use in patients with hepatic impairment is not recommended ( 5.4 ) Use with caution in patients with a history of urinary retention, angle-closure glaucoma, increased intraocular pressure and in patients taking anticholinergic medications ( 5.5 ) 5.1 Serotonin Syndrome The development of a potentially life-threatening serotonin syndrome has been reported with cyclobenzaprine when used in combination with other drugs, such as selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), tramadol, bupropion, meperidine, verapamil, or MAO inhibitors. The concomitant use of cyclobenzaprine hydrochloride extended-release capsules with MAO inhibitors is contraindicated [see Contraindications ( 4 )]. Serotonin syndrome symptoms may include mental status changes (e.g., confusion, agita...

Adverse reactions (label)

The following clinically significant reactions are described in greater detail, in other sections. Serotonin Syndrome [see Warnings and Precautions ( 5.1 )] Adverse Cardiovascular Effects [see Warnings and Precautions ( 5.2 )] Most common adverse reactions (incidence ≥3% in any treatment group and greater than placebo): dry mouth, dizziness, fatigue, constipation, nausea, dyspepsia, and somnolence ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Teva Pharmaceuticals at 1-888-483-8279 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. The data described below reflect exposure to cyclobenzaprine hydrochloride extended-release capsules in 253 patients in 2 clinical trials. Cyclobenzaprine hydrochloride extended-release capsules were studied in two double-blind, parallel-group, placebo-controlled, active-controlled trials of identical design [see Clinical Studies ( 14 )] . The study ...

Source: FDA SPL label for Cyclobenzaprine Hydrochloride (Advanced Rx of Tennessee, LLC), effective 20241029. Full label on DailyMed.

Side-effect reports sent to the FDA

These are counts of reports people filed, not rates of harm. Anyone can file one, and nobody checks whether the drug was the cause. Millions of doses are taken for every report sent, so the useful part is how this drug compares with the average across all drugs.

62,900reports that mention this drug
62,810of those blame this drug, not another one the person was taking
63%of reports describe a serious outcome, such as a hospital stay (average for all drugs: 57%)
10.4%of reports include a death, from any cause (average for all drugs: 9.1%)

Problems reported most often

Pain · 6,013Fatigue · 5,249Drug Ineffective · 4,636Nausea · 4,453Headache · 4,416Off Label Use · 3,664Diarrhoea · 3,439Chronic Kidney Disease · 3,299Arthralgia · 3,093Fall · 3,009Dizziness · 2,703Back Pain · 2,644Dyspnoea · 2,644Vomiting · 2,495Constipation · 2,466

Reports per year

20192020202120222023202420252026
6,9556,2814,9934,2804,0464,0254,4352,326

1,454 reports blaming this drug for every million Medicare prescriptions filled, which is 0.5× the typical drug on this site. (10,767 reports in 2024–2026, against 7,407,401 Medicare fills in one year. This is the one number here that accounts for how many people take the drug.)

Source: the FDA's Adverse Event Reporting System (FAERS). Reports are voluntary and unverified. Drugs that are prescribed a lot, in the news, or in lawsuits attract more reports, so the percentages are compared with the whole database to correct for that partly, not fully.

Recalls and regulatory record

1recall actions on file
3 / 23brand / generic applications
1label changes since 2021
NoREMS program
DateClassFirmReason
08/2025Class IUnichem Pharmaceuticals USA Inc.Labeling: Label Mix Up; Bottles of Meloxicam USP, 7.5mg, 90-count tablets (yellow in color), were labeled as Cyclobenzaprine Hydrochloride Tablets USP, 10 mg 90-count tablets (blue in color).

Class I = reasonable probability of serious harm. Class II = temporary or reversible harm. Class III = unlikely to harm. Most generic recalls are manufacturing or labeling defects for one lot, not a verdict on the molecule.

Evidence base

38randomized trials (PubMed)
4systematic reviews
64registered trials
66%of completed trials posted results
20%terminated or withdrawn
64%industry-funded

Independent Cochrane reviews

Counts measure how much evidence exists and how transparent it is, not how big the benefit is. For that, ask your prescriber: if 100 people like me took this, how many would get better because of it, and how many would be harmed? (Doctors call these the "number needed to treat" and "number needed to harm.") It differs by condition and is the number drug ads leave out. Sources: PubMed, ClinicalTrials.gov.

Money and lawsuits

In 2024, drug companies reported $0 in payments to US physicians and hospitals tied to this drug across 0 transactions.

No pending federal MDL names this drug or its brands.

Not named in any federal pharmaceutical settlement of $100M or more on record.

Sources: CMS Open Payments (Sunshine Act); Judicial Panel on Multidistrict Litigation pending docket list; DOJ settlements as tabulated on Wikipedia with links to the primary record. State-court and individual suits are not included.

Who takes it and what it costs

2,727,309Medicare Part D patients (2024)
7,407,401prescriptions filled
$9average cost per fill
$64Mtotal Medicare spend
ProductFills$/fill
Cyclobenzaprine HCl7,401,986$8
Cyclobenzaprine HCl ER5,267$351
Amrix148$3,027

Same-class alternatives

No same-class alternatives found in RxClass.

Questions to ask your prescriber

  1. The most-reported problems in FDA's adverse event data are pain, fatigue, nausea. How would we recognize and handle those?
  2. Off-label use is among the most-reported items for this drug. Is my use on-label, and if not, what evidence supports it?
  3. What result are we expecting, by when, and what is the plan if it does not happen?
  4. If 100 people like me took this drug, how many would actually get better because of it, and how many would be harmed by it? (Doctors call these the number needed to treat and the number needed to harm.)