What Cyclobenzaprine Is:
Cyclobenzaprine is a muscle relaxer that is available in generic form as well as under the brand names Flexeril and Amrix.
This drug also has mild effects similar to those of tricyclic antidepressants.
It's not FDA-approved for fibromyalgia, but it is frequently prescribed off-label for people with this condition.
What Cyclobenzaprine Does:
Cyclobenzaprine relaxes your muscles by acting on your central nervous system. Doctors 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.
Cyclobenzaprine for Fibromyalgia:
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.
Some older studies pointed to improvements in the short term, but no significant long-term improvement.
Most recently, 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.
A typical adult dosage of cyclobenzaprine is between 5 and 10 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.
Cyclobenzaprine Side Effects:
Some side effects of cyclobenzaprine are serious enough that you should report them to your doctor 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
- Nausea or vomiting
Less serious side effects include:
- Dry mouth
- Blurred vision
- Loss of appetite
- Stomach pain
- Diarrhea, constipation or gas
Cantini F, et al. Minerva medica. 1994 Mar;85(3):97-100. Abstract only, article in Italian. Fluoxetin combined with cyclobenzaprine in the treatment of fibromyalgia.
Carette S, et al. Arthritis and rheumatism. 1994 Jan;37(1):32-40. Comparison of amitriptyline, cyclobenzaprine, and placebo in the treatment of fibromyalgia. A randomized, double-blind clinical trial.
Moldofsky H, et al. Journal of rheumatology. 2011 Dec;38(12):2653-63. Effects of bedtime very low dose cyclobenzaprine on symptoms and sleep physiology in patients with fibromyalgia syndrome: a double-blind randomized placebo-controlled study.
Santandrea S, et al. The Journal of international medical research. 1993 Mar-Apr;21(2):74-80. A double-blind crossover study of two cyclobenzaprine regimens in primary fibromyalgia syndrome.
Smith B, et al. Drug Class Reviews. Oregon Health & Science University; 2011 Apr. Drugs for Fibromyalgia: Final Original Report.
Tofferi JK, Jackson JL, O'Malley PG. Arthritis and rheumatism. 2004 Feb 15;51(1):9-13. Treatment of fibromyalgia with cyclobenzaprine: A meta-analysis.