- Generic name: Cyclobenzaprine hydrochloride
- Brand names: Flexeril, Fexmid, Amrix
- Dosages: 5 mg, 10 mg tablets
- Pharmacologic category: Skeletal muscle relaxant
- FDA approved: August 26, 1977
- Habit forming? Possibly
- Pregnancy risk factor: B
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Medical uses
Cyclobenzaprine is a centrally acting muscle relaxant, intended
for short-term use in the treatment of pain, tenderness, and limitation
of motion caused by muscle spasms.
The most common side effects are drowsiness, dry mouth, fatigue and headache.
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Cyclobenzaprine for fibromyalgia
Cyclobenzaprine 10 mg (Flexeril) may be prescribed to treat the pain, stiffness,
and sleep problems that occur with fibromyalgia. This is currently
an unlabeled use of the drug.
For use in treating fibromyalgia, the usual starting dosage is 5 to 10 mg at bedtime.
How well Cyclobenzaprine works
People with fibromyalgia who take cyclobenzaprine seem to notice
an overall improvement in their symptoms, and they especially
note improved sleep1.
The medicine's effects may decrease over time2.
Experts do not know exactly how this drug works to improve fibromyalgia.
Cyclobenzaprine is chemically similar to amitriptyline,
a tricyclic antidepressant, so researchers believe that the two
drugs may work in similar ways.
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Pharmacological characteristics
- Elimination half-life: eliminated
quite slowly, with an effective half-life of 18 hours (range
8-37 hours.
- Metabolism: Hepatic via CYP3A4, 1A2, and 2D6; may undergo
enterohepatic recirculation.
- Excretion: Excreted primarily via kidneys.
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Benefits
- Quick and lasting relief of back pain, neck pain and muscle spasms
- If taken at bedtime may help with insomnia due to the pain and spasms
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Concerns
- Poorly tolerated: sedation and other CNS side effects are very common
- Morning "hangover"
- Range of toxicity is similar to tricyclic antidepressant overdose.
Anticholinergic symptoms predominate, extreme cases may manifest
with cardiac dysrhytmias and seizures.
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Unlabeled uses
- Fibromyalgia. Cyclobenzaprine have been used with some
success to treat some fibromyalgia patients. It is administered to fibromyalgia patients typically in
a dosage range of 5 to 30 mg per day.
Data generally support its use in treating sleep and pain, and
there are some data suggesting synergism when cyclobenzaprine
is used with fluoxetine.
- Tension headache3
- Insomnia
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Mechanism of action
Cyclobenzaprine is a centrally-acting skeletal muscle relaxant
pharmacologically related to tricyclic antidepressants. It relieves
skeletal muscle spasms of local origin without interfering with
muscle function by acting within CNS at brain stem (reduces tonic
somatic motor activity influencing both alpha and gamma motor neurons).
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Reviews, Discussions Boards & Forums
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References
- 1. Tofferi JK, et al. (2004). Treatment
of fibromyalgia with cyclobenzaprine: A meta-analysis. Arthritis
and Rheumatism, 2004 Feb 15;51(1):9-13. PubMed
- 2. Moldofsky H. Management of unrefreshing sleep
in fibromyalgia. Rheum Dis Clin North Am. 2002 May;28(2):353-65.
PubMed
- 3. Lance JW, Anthony M. Cyclobenzaprine
in chronic tension headache. Med J Aust 1972;
2:1409–1411
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