Cyclobenzaprine: 7 things you should know
Medically reviewed by Carmen Fookes, BPharm Last updated on Sep 2, 2019.
1. How it works
- Cyclobenzaprine relaxes muscles by reducing muscle hyperactivity through an action on both gamma and alpha motor systems (these are nerve fibers that directly connect with skeletal muscle and are responsible for muscle contraction). Cyclobenzaprine acts primarily through the brain stem rather than the spinal cord and does not act directly on skeletal muscle.
- Cyclobenzaprine will not reduce muscle spasm due to central nervous system (CNS) disease, such as cerebral palsy.
- Cyclobenzaprine belongs to a class of drugs known as muscle relaxants.
- Relieves muscle spasm associated with acute, painful, musculoskeletal conditions.
- Improves pain, tenderness, and range of motion associated with muscle spasms and increases a person's ability to perform their day-to-day activities.
- Cyclobenzaprine is the most studied skeletal muscle relaxant.
- Relieves skeletal muscle spasm without interfering with muscle function.
- The sedative effects of cyclobenzaprine may help those experiencing insomnia as a result of muscle spasms.
- Long-lasting effects.
- Cyclobenzaprine has not been associated with addiction; however, abrupt discontinuation may produce symptoms such as nausea, headache, and a general feeling of discomfort. The dosage of cyclobenzaprine is best tapered off slowly on discontinuation.
- Generic cyclobenzaprine is available.
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Sedation. This is a major side effect and it may impair reaction skills and affect a person's ability to drive or operate machinery. Avoid alcohol
- Other common side effects include dry mouth, fatigue, difficulty with urination, an increase in eye pressure, headache, dizziness, blurred vision, or nausea
- Should only be used short-term (for periods of up to two to three weeks only)
- Not effective for muscle spasms occurring as a result of cerebral or spinal cord disease, or in children with cerebral palsy
- Cyclobenzaprine should never be given within 14 days of monoamine oxidase (MAO) inhibitor antidepressants, as the combination may be fatal
- Interaction with other drugs that also increase serotonin (such as antidepressants, tramadol, St John's Wort, bupropion) may cause serotonin syndrome. Symptoms include mental status changes (such as agitation, hallucinations, coma, delirium), fast heart rate, dizziness, flushing, muscle tremor or rigidity and stomach symptoms (including nausea, vomiting, and diarrhea)
- Cyclobenzaprine may enhance the effects or side effects of tricyclic antidepressants (for example, amitriptyline and imipramine), alcohol, and other CNS depressants
- May not be suitable for people with arrhythmias, heart block or conduction disturbances, heart failure, hyperthyroidism, or immediately following a heart attack
- The dosage of cyclobenzaprine should be reduced in people with mild liver disease. It should not be taken by people with moderate-to-severe liver disease
- Cyclobenzaprine may not be suitable for people with glaucoma or increased intraocular pressure, a history of urinary retention, or taking other drugs that also have anticholinergic side effects (anticholinergic side effects include constipation, blurred vision and increase in eye pressure)
- Elderly people may be more sensitive to the effects of cyclobenzaprine, and the dosage should be kept low if the benefits of using it in seniors outweigh the risks.
Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.
- Cyclobenzaprine may be taken with or without food.
- Cyclobenzaprine should be taken in addition to rest and physical therapy.
- The effective dosage of cyclobenzaprine varies between individuals. Take cyclobenzaprine exactly as directed by your doctor. Talk with your doctor if you experience any worrying side effects or cyclobenzaprine is not effective.
- Cyclobenzaprine is usually only given for a maximum of two to three weeks. Your doctor may advise tapering off the dose slowly when it is time to discontinue it.
- Cyclobenzaprine is likely to make you sleepy or impair your judgment time. Avoid operating machinery, driving, or performing tasks that require mental alertness while taking this medicine.
- Avoid alcohol while taking this medicine. Alcohol may potentiate the side effects of cyclobenzaprine.
- Talk to your doctor or pharmacist before taking any other medications while you are taking cyclobenzaprine. Contact your doctor urgently if you experience any mental status changes (such as agitation, hallucinations, coma, delirium), fast heart rate, dizziness, flushing, muscle tremor or rigidity and stomach symptoms (including nausea, vomiting, and diarrhea).
- Tell your doctor if you have a heart condition, thyroid disease, liver disease, glaucoma or a problem with urination before starting treatment.
6. Response and Effectiveness
- The time to the peak concentration of cyclobenzaprine varies depending on the formulation taken (around 7 hours for the extended-release form). Some effects may be noted within 20 to 30 minutes. The effects of immediate-release tablets last for four to six hours. The effects of extended-release tablets last for 24 hours.
- 5mg of cyclobenzaprine is reportedly as effective as 10mg of cyclobenzaprine, with fewer side effects.
- Cyclobenzaprine is ineffective in muscle spasm due to brain injury or disease.
Medicines that interact with cyclobenzaprine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with cyclobenzaprine. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.
Common medications that may interact with cyclobenzaprine include:
- anti-anxiety medications
- antidepressants, such as amitriptyline, imipramine, nortriptyline
- antihistamines that cause sedation, such as diphenhydramine
- monoamine oxidase inhibitors, such as selegiline, isocarboxazid, or phenelzine (interaction may be life-threatening)
- opioid analgesics such as oxycodone and morphine
- other muscle relaxants such as methocarbamol
- sleeping pills, such as zolpidem
- some chemotherapy treatments
- some medications used to treat mental illness, such as clozapine and thioridazine
Alcohol may worsen the side effects of cyclobenzaprine such as drowsiness and dizziness.
Note that this list is not all-inclusive and includes only common medications that may interact with cyclobenzaprine. You should refer to the prescribing information for cyclobenzaprine for a complete list of interactions.
Cyclobenzaprine [Package Insert]. Revised 04/2019. Drugs.com https://www.drugs.com/ppa/cyclobenzaprine.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use cyclobenzaprine only for the indication prescribed.
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