- 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
Medical uses
Cyclobenzaprine hcl is a centrally acting muscle relaxant, intended for short-term treatment of pain, tenderness, and limitation of motion caused by muscle spasms.
The most common side effects are drowsiness, fatigue, dizziness, dry mouth, and headache.
Cyclobenzaprine as Sleep Aid
Cyclobenzaprine (Flexeril) is used off-label as a sleep aid. It is especially helpful for pain-related insomnia, providing to the body the opportunity to heal and repair5. Cyclobenzaprine is also often prescribed for sleep problems that occur with fibromyalgia4.
Cyclobenzaprine has structure and pharmacological properties quite similar to amitriptyline, which may partly account for its sedating properties.
Cyclobenzaprine dosage for sleep problems: 1 mg to 10 mg at bedtime4 helps to stay asleep longer and to get more restorative sleep. Very low bedtime dosing provides lower blood levels of drug the next day and may reduce unwanted next-day somnolence and drowsiness.
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.
- Bioavailability: from 33% to 55%.
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
Concerns
- Poorly tolerated: sedation and other CNS side effects are very common
- Next-day hangover-like effects.
- Cardiovascular toxicity in overdose. Anticholinergic symptoms predominate, extreme cases may manifest with cardiac dysrhytmias and seizures.
- Cylcobenzaprine is absolutely contraindicated in patients with recent heart attack, arrhythmias, heart block or conduction disturbances, heart failure, or hyperthyroidism.
- Cyclobenzaprine may intensify the effects of alcohol, barbiturates, and other CNS depressants.
Unlabeled uses
- Fibromyalgia. Cyclobenzaprine have been used with some success to treat some fibromyalgia patients2. It is administered to fibromyalgia patients typically in a dosage range of 5 to 30 mg per day.
Clinical data supports its use in treating sleep and pain, and there is some evidence suggesting synergism when cyclobenzaprine is used with fluoxetine.
- Tension headache3
- Insomnia
Mechanism of action
Cyclobenzaprine is a centrally-acting skeletal muscle relaxant pharmacologically related to tricyclic antidepressants. Currently experts do not know exactly how this drug works.
Cyclobenzaprine 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). It has prominent antimuscarinic activity.
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References
- 1. Tofferi JK, et al. 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
- 4. Moldofsky H, Harris HW, Archambault WT, Kwong T, Lederman S. Effects of bedtime very low dose cyclobenzaprine on symptoms and sleep physiology in patients with fibromyalgia syndrome. J Rheumatol. 2011 Dec;38(12):2653-63 PubMed
- 5. See S, Ginzburg R. Choosing a skeletal muscle relaxant. Am Fam Physician. 2008 Aug 1;78(3):365-70. PubMed
By HealthyStock Research Group, September 2009
Medical resources reviewed: August 2018
