Cyclobenzaprine is a muscle relaxer that is available in generic form as well as under the brand names Flexeril and Amrix. It’s considered a second-line treatment for fibromyalgia.
This drug is a derivative of tricyclic antidepressants, which are commonly prescribed for this condition, and has similar, mild effects.
Cyclobenzaprine isn’t approved by the U.S. Food and Drug Administration (FDA) for fibromyalgia, but it is frequently prescribed off-label for it. In 2024, a sublingual form (Tonmya) was fast-tracked for approval for fibromyalgia.
Cyclobenzaprine relaxes your muscles by acting on your central nervous system. Healthcare providers often prescribe it for muscle injuries as well as for chronic pain.
In studies, this drug has been found to improve sleep quality as well.
Fibromyalgia Studies
Cyclobenzaprine has been studied as a potential fibromyalgia treatment since the 1980s with mixed results.
A 2011 review of drugs used for fibromyalgia found that only one of the three trials included showed that cyclobenzaprine reduced the pain of fibromyalgia. The successful trial also showed improvements in sleep, as well as overall improvement. However, the researchers found no significant differences in stiffness, fatigue, tender points, muscle tightness, or total pain load.
The review found that results from smaller trials were often not significant, possibly because they included too few people.
An earlier analysis of medical literature says that fibromyalgia patients taking cyclobenzaprine were three times as likely to report better sleep, fewer symptoms, and more overall improvement than people in control groups.
In 2011, a small study focused on sleep physiology concluded that very low-dose cyclobenzaprine improved the quality of sleep in people with fibromyalgia. Researchers said they also saw improvements in pain, tenderness, and depression.
Dosage
A typical adult dosage of cyclobenzaprine is between 5 and 10 milligrams (mg) taken up to three times a day. An extended-release form, which is generally taken in doses of 15 to 30 mg once a day, is also available.
In the fibromyalgia trial on sleep physiology, participants were given steadily escalating doses of 1 to 4 mg taken only at bedtime.
Lower dosages are typically linked to fewer side effects.
Side Effects
Some side effects of cyclobenzaprine are serious enough that you should report them to your healthcare provider immediately. They include:
- Allergic reaction (rash, hives, swelling of the face, lips or tongue)
- Chest pain or heaviness, especially with pain spreading to the shoulder or arm
- Rapid, pounding or uneven heartbeat
- Sudden numbness or weakness
- Confusion or loss of coordination
- Sudden headache
- Hallucinations
- Seizures
- Nausea or vomiting
Less serious side effects include:
- Dry mouth
- Blurred vision
- Sleepiness
- Loss of appetite
- Stomach pain
- Diarrhea, constipation, or gas
This medical should not be mixed with alcohol or other sedating medications, such as narcotics or sleep aids.
