Product Description

Cyclobenzaprine is a skeletal muscle relaxant and a central nervous system (CNS) depressant. It is marketed as Flexeril (5 and 10 mg tablets). Both the 5 and 10 milligram tablets are available generically.

Mechanism of action

The exact mechanism of action for cyclobenzaprine is unknown. Current research appears to indicate that cyclobenzaprine acts on the locus coeruleus where it results in increased norepinephrine release, potentially through the gamma fibers which innervate and inhibit the alpha motor neurons in the vetral horn of the spinal cord. Decreased firing of the alpha motor neuron results in decreased muscular tone.

Indications

Cyclobenzaprine is typically prescribed to relieve pain and muscle spasms. Typically, muscle spasms occur in an injury to stabilize the affected body part and prevent further damage. The spasm of the muscles can increase the pain level. It is believed that by decreasing muscular spasm, pain is diminished. A common application would be that of a whiplash injury in a car accident. Muscle relaxants such as Cyclobenzaprine (Flexeril) and Orphenadrine Citrate (Norflex) have also been studied in the treatment of fibromyalgia. In a study of 120 fibromyalgia patients, those receiving Cyclobenzaprine (10 to 40 mg) over a 12 week period had significantly improved quality of sleep and pain score. There was a trend towards improvement in fatigue symptoms but not in duration of morning stiffness. Interestingly, there was also a reduction in the total number of tender points and muscle tightness.

It is also prescribed off-label as a sleep-aid.

Side effects

Common side effects include drowsiness, dizziness, and blurred vision. Other side effects are respiratory depression and decreased functionality in various muscles. Long term use has been associated with vision damage.

Interactions

When you are taking cyclobenzaprine, it is especially important that your health care professional know if you are taking any of the following:
Alcohol or
Central nervous system (CNS) depressants (medicines that cause drowsiness) or
Tricyclic antidepressants (amitriptyline [eg. Elavil], amoxapine [eg. Asendin], clomipramine [eg. Anafranil], desipramine [eg. Pertofrane], doxepin [eg. Sinequan], imipramine [eg. Tofranil], nortriptyline [eg. Aventyl], protriptyline [eg. Vivactil], trimipramine [eg. Surmontil])—The chance of side effects may be increased
Monoamine oxidase (MAO) inhibitors (furazolidone [eg. Furoxone], phenelzine [eg. Nardil], procarbazine [eg. Matulane], selegiline (eg. Eldepryl), tranylcypromine [eg. Parnate])—Taking cyclobenzaprine while you are taking or within 2 weeks of taking MAO inhibitors may increase the chance of side effects

Legality

Cyclobenzaprine is regulated in the U.S. for prescription use only. Cyclobenzaprine is unscheduled, however, and it is not illegal to have cyclobenzaprine in your possession, even without a prescription.

Abuse

Cyclobenzaprine is not widely abused, despite having an arguably high potential for abuse.

When used for illicit purposes, the drug is often referred to as "cyclone" with recreational doses ranging from 20 to 80 mg. At these dosages, users report mild to moderate drowsiness and relaxation as the primary effects. Compared with other commonly abused CNS depressants, cyclobenzaprine's effects are considered to be mild, limiting its popularity as a recreational drug.

Cyclobenzaprine, on the other hand, can induce moderate to severe anticholinergic effects at higher doses, as well as benzodiazepine-like sedation and often pleasurable muscle-relaxation. At even higher doses, cyclobenzaprine may cause severe ataxia, and due to excessive muscle-relaxation, and possibly disorienting side effects such as a floating sensation or other imagined movements (usually experienced when at rest.)

Overdose

Although purportedly unpleasant, cyclobenzaprine is relatively benign in case of overdose, depending on its toxicity level in the user, and also on the susceptibility of the user to possibly harmful effects of overdose. Note that the susceptibility to these potentially damaging effects is greatly increased when cyclobenzaprine is used in conjunction with other drugs, particularly Central Nervous System Depressants and other antidepressants. Use of cyclobenzaprine with a MAOI (Mono Amine Oxidase Inhibitor) will very possibly result in fatality.