Cyclobenzaprine: uses, dosing, side effects & brands

Cyclobenzaprine hydrochloride is a skeletal muscle relaxant which relieves muscle spasm of local origin without interfering with muscle function.

The FDA classifies cyclobenzaprine as a muscle relaxant. Most muscle relaxants work in the brain and spinal cord rather than on the muscle itself: they damp down the overactive nerve signals and reflexes that keep muscles tense, easing spasms and tightness. Some specialized agents instead act directly on muscle calcium release. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.

The label's WARNINGS section states that cyclobenzaprine may enhance the effects of alcohol, barbiturates, and other CNS depressants. Because cyclobenzaprine is closely related to the tricyclic antidepressants and is sedating, combining it with alcohol adds to central-nervous-system depression, so caution is advised with alcohol use during treatment. This is what cyclobenzaprine's FDA label says; alcohol advice depends on your dose and health, so confirm with your pharmacist.

Under DRUG ABUSE AND DEPENDENCE the label notes that, given the pharmacologic similarities to tricyclic drugs, certain withdrawal symptoms should be considered even though they have not been reported with cyclobenzaprine itself. It states that abrupt cessation of treatment after prolonged administration rarely may produce nausea, headache, and malaise, and that these are not indicative of addiction. The label does not carry a boxed warning and does not describe a life-threatening withdrawal, so any decision to stop after prolonged use should be managed by the prescribing clinician. Do not stop cyclobenzaprine on your own — any change is a prescriber-managed decision.

The elimination half-life of cyclobenzaprine is about 18 hours (range roughly 8 to 37 hours) for the standard immediate-release tablet in typical adults — that is how long the body takes to clear half of a dose. Half-life varies by formulation and population: it is longer with the extended-release capsule (about 32 hours) and in adults over 65 (up to about 50 hours), and hepatic impairment roughly doubles drug exposure; no active metabolite with a materially longer half-life is described. Half-life is not the same as how long a drug test can detect the drug, and it varies with age, kidney and liver function.

It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run cyclobenzaprine against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.

We track 3 cyclobenzaprine-containing products in the U.S.: Amrix, Flexeril and Tonmya. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.

Across the brands we track, cyclobenzaprine is currently marketed as capsule, extended release, tablet and tablet, orally disintegrating, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.

We do not currently list a generic-labelled cyclobenzaprine product. That does not always mean none exists — it means none appears under a generic name in the FDA data we track. Ask your pharmacist.

The FDA's Enforcement database lists 1 recall record whose product description mentions cyclobenzaprine. The most recent: Cyclobenzaprine Hydrochloride Tablets (Aug 27, 2025). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.

Cyclobenzaprine works fairly quickly. Taken for muscle spasm, it usually starts to relax muscles and ease pain within about an hour, with the effect building over the next few hours. It's meant for short-term use, generally no more than two to three weeks, alongside rest and physical therapy. Drowsiness often sets in during that same first hour, so plan around it.

Alcohol: the FDA label flags alcohol as something to be careful with — see the alcohol section above for what it actually says. Other medicines: we hold source-cited interaction answers for Can you take Flexeril with ibuprofen? and Can you take Benadryl and Flexeril (cyclobenzaprine) together?. This is what the FDA label and our cited sources say — it is not a complete list. Your pharmacist can check your own combination.

No. Cyclobenzaprine is a muscle relaxant, not an opioid, and is not a DEA-scheduled controlled substance. It is closely related to tricyclic antidepressants in structure, is quite sedating, and should not be combined with alcohol or other depressants — but it is not classed as a narcotic.

Drowsiness is by far the most common, reported by about 29% of people on the 5 mg dose, followed by dry mouth (about 21%) and fatigue (about 6%), per the FDA label. MedlinePlus also lists dizziness, nausea, constipation, and heartburn as typical, milder effects. Because cyclobenzaprine is structurally a tricyclic, this sedation and dry mouth reflect its strong anticholinergic action — do not drive a car or operate machinery until you know how Flexeril affects you, as MedlinePlus warns.

Seek emergency care for signs of serotonin syndrome. The FDA label states “The development of a potentially life-threatening serotonin syndrome has been reported with cyclobenzaprine hydrochloride 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.” MedlinePlus says to call your doctor immediately for “agitation, fever, sweating, confusion, fast or irregular heartbeat, shivering, severe muscle stiffness or twitching, hallucinations,” as well as an “irregular or fast heart rate,” chest pain, or “rash, itching, hives, swelling of the face or tongue, or difficulty breathing or swallowing.” These can be emergencies.

The FDA label contraindicates cyclobenzaprine in the “acute recovery phase of myocardial infarction, and patients with arrhythmias, heart block or conduction disturbances, or congestive heart failure,” and in hyperthyroidism. It is also contraindicated with MAO inhibitors or “within 14 days after their discontinuation,” because hyperpyretic crisis, seizures, and deaths have occurred with this combination. For adults 65 and older, the American Geriatrics Society Beers Criteria list cyclobenzaprine among muscle relaxants to avoid because of strong anticholinergic effects, sedation, fall risk, and questionable effectiveness at tolerated doses; the label itself says in the elderly it “should be used only if clearly needed” and started at 5 mg. This is not a complete list — tell your prescriber your full history and medication list.

It is not intended for long-term use. MedlinePlus states plainly: “Do not take this drug for more than 3 weeks without talking to your doctor.” Cyclobenzaprine was only studied as a short-term add-on to rest and physical therapy for acute muscle spasm, and its usefulness beyond 2 to 3 weeks is not established per the FDA label. Prolonged use also prolongs exposure to its sedating, anticholinergic effects. Do not stop or extend a prescription on your own — discuss the plan with your prescriber.

Drowsiness and dry mouth typically begin with the first doses, since the drug takes effect within about an hour and has a long half-life, so daytime grogginess can carry over — a key reason for the do-not-drive warning. Many people find the sedation eases over the first days as they adjust, but it can persist the whole course. Because Flexeril is usually prescribed for only 2 to 3 weeks, most side effects resolve after the short course ends. Contact your prescriber if drowsiness is severe or if any serious symptom above appears.

Cyclobenzaprine is a muscle relaxant FDA-approved for short-term relief of muscle spasm from acute, painful musculoskeletal conditions — think a back or neck strain. It's meant to be used alongside rest and physical therapy for two to three weeks at most; there's no evidence it helps beyond that. It works in the brain and spinal cord, not directly on the muscle, and it's chemically related to tricyclic antidepressants, which is why it's so sedating.

Yes. Low-dose cyclobenzaprine, often taken at bedtime, is prescribed off-label for fibromyalgia to improve sleep and reduce muscle pain, and some studies support a modest benefit. This is not an FDA-approved use, and it remains off-label — the drug is officially cleared only for short-term muscle spasm. Because it causes drowsiness and dry mouth and can interact dangerously with MAOI antidepressants, it should be used under a prescriber's guidance.