Cyclobenzaprine is a skeletal muscle relaxant. The indication for use is relief of pain associated with painful musculoskeletal conditions. How Cyclobenzaprine relieves pain from muscle spasm is not fully understood; however, it is believed to work on the central nervous system at the brain stem level or in the spinal cord. The National Institute of Health (NIH) reports that cyclobenzaprine relieves the pain and tenderness associated with muscle spasm and improves overall ability to complete activities of daily living.
Central Nervous System Side Effects
According to the NIH the most commonly reported central nervous system side effects are dry mouth, drowsiness and dizziness. Fatigue, headache, and confusion may occur, as well as weakness and blurred vision.
The NIH reported rare occurrence (less than 1 in 100 patients) of muscle twitching, convulsions, syncope (fainting), disorientation, anxiety, insomnia, depressed mood, abnormal thinking and dreaming, and hallucinations.
Cardiovascular Side Effects
Cyclobenzaprine may have cardiovascular effects to include arrhythmias (irregular heart rate and rhythm), low blood pressure and myocardial infarction (heart attack).
Gastrointestinal Side Effects
Dry mouth, nausea and vomiting, indigestion, and an unpleasant taste in the mouth may occur with use of cyclobenzaprine. Rarely, abnormal liver function such as hepatitis or jaundice may occur.
Genitourinary Side Effects
Cyclobenzaprine can cause urinary frequency or urinary retention. Cyclobenzaprine should be used cautiously in patients with a history of urinary retention.
General Side Effects
Other general side effects of cyclobenzaprine reported by the NIH include rash, itching, facial edema (swelling) and edema of the tongue, thirst and abdominal pain. Ageusia (impairment of taste) and tinnitus (ringing in the ears) have also been reported.
Warnings
Although side effects are expected when taking cyclobenzaprine, any adverse side effects should be reported to a healthcare provider, especially when intolerable or potentially severe and life threatening.
Cyclobenzaprine should be used cautiously or avoided in patients with a history of angle-closure glaucoma, urinary retention or increased intraocular pressure.
Because of sedation, patients should avoid driving or any other activities that require alertness. Increased sedation occurs with concomitant use of alcohol, barbiturates and other central nervous system depressants.
The NIH reports that patients who took cyclobenzaprine while using monoamine oxidase inhibitors and tricyclic antidepressants have experienced serious adverse effects to include convulsions, arrhythmias, myocardial infarctions, stroke and death. Concomitant use should be avoided.
References
- National Institute of Health Daily Med Sheets
- Lippincott's Nursing Drug Guide, Karch, A. M., 2008
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