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 antidepressants. Use of cyclobenzaprine with an MAOI (monoamine oxidase inhibitor) will very possibly result in fatality. A case of rhabdomyolysis (muscle breakdown) associated with its overdose has been reported in the scientific literature. This is a rare though potentially fatal complication. Treatment protocols and support should follow the same as for any tricyclic anti depressant
Friday, 21 September 2007
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
- Central nervous system (CNS) depressants (medicines that cause drowsiness) or
- Tricyclic antidepressants (amitriptyline [e.g., Elavil], amoxapine [e.g., Asendin], clomipramine [e.g., Anafranil], desipramine [e.g., Pertofrane], doxepin [e.g., Sinequan], imipramine [e.g., Tofranil], nortriptyline [e.g., Aventyl], protriptyline [e.g., Vivactil], trimipramine [e.g., Surmontil])—The chance of side effects may be increased
- Monoamine oxidase (MAO) inhibitors (furazolidone [e.g., Furoxone], phenelzine [e.g., Nardil], procarbazine [e.g., Matulane], selegiline (e.g., Eldepryl), tranylcypromine [e.g., Parnate])—Taking cyclobenzaprine while you are taking or within 2 weeks of taking MAO inhibitors may increase the chance of side effects
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. 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.
To avoid possible stomach sickness, take with food and a full glass of water.
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 ventral horn of the spinal cord.[1] Decreased firing of the alpha motor neuron results in decreased muscular tone. Cyclobenzaprine is a muscle relaxant acting primarily on the central nervous system. It is structurally similar to Amitriptyline, differing by only one double bond. Cyclobenzaprine is a weak inhibitor of presynaptic norepinephrine and serotonin. Skeletal muscle relaxant activity is due to brainstem mediated inhibition of gamma motor neurons[
Systematic (IUPAC) name
 | |
| Cyclobenzaprine | |
| Systematic (IUPAC) name | |
| 3-(5H-dibenzo[a,d]cyclohepten-5-ylidene)- N,N-dimethyl-1-propanamine | |
| Identifiers | |
| CAS number | |
| ATC code | M03 |
| PubChem | |
| DrugBank | |
| Chemical data | |
| Formula | C20H21N |
| Mol. mass | 275.387 g/mol |
| Pharmacokinetic data | |
| Bioavailability | 33% to 55% |
| Metabolism | hepatic |
| Half life | 18 hours (range 8-37 hours; n=18) |
| Excretion | ? |
| Therapeutic considerations | |
| Pregnancy cat. | Category B |
| Legal status | Unscheduled |
| Routes | ? |