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Cyclobenzaprine (Systemic)

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Cyclobenzaprine (Systemic)

US Brand Names

• Flexeril

Canadian Brand Names

• Flexeril


Cyclobenzaprine (sye-kloe-BEN-za-preen) is used to help relax certain muscles in your body. It helps relieve the pain, stiffness, and discomfort caused by strains, sprains, or injuries to your muscles. However, this medicine does not take the place of rest, exercise or physical therapy, or other treatment that your doctor may recommend for your medical problem. Cyclobenzaprine acts on the central nervous system (CNS) to produce its muscle relaxant effects. Its actions on the CNS may also cause some of this medicine's side effects.

Cyclobenzaprine may also be used for other conditions as determined by your doctor.

Cyclobenzaprine is available only with your doctor's prescription, in the following dosage form:


    • Tablets (U.S. and Canada)

Special Considerations

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For cyclobenzaprine, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to cyclobenzaprine. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.


Studies on birth defects with cyclobenzaprine have not been done in humans. However, cyclobenzaprine has not been shown to cause birth defects or other problems in animal studies.


It is not known whether cyclobenzaprine passes into breast milk. Although most medicines pass into the breast milk in small amounts, many of them may be used safely while breast-feeding. Mothers who are taking this medicine and who wish to breast-feed should discuss this with their doctor.


Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of cyclobenzaprine in children with use in other age groups.


Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of cyclobenzaprine in teenagers up to 15 years of age with use in other age groups.

Older adults

Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information comparing use of cyclobenzaprine in the elderly with use in other age groups.

Other medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. 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 [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

Other medical problems

The presence of other medical problems may affect the use of cyclobenzaprine. Make sure you tell your doctor if you have any other medical problems, especially:

    • Glaucoma or

    • Problems with urination-Cyclobenzaprine can make your condition worse

    • Heart or blood vessel disease or

    • Overactive thyroid-The chance of side effects may be increased


Take this medicine only as directed by your doctor. Do not take more of it and do not take it more often than your doctor ordered. To do so may increase the chance of serious side effects.


The dose of cyclobenzaprine will be different for different people. Follow your doctor's orders or the directions on the label . The following information includes only the average doses of cyclobenzaprine. If your dose is different, do not change it unless your doctor tells you to do so.

    • For the oral dosage form (tablets):

      o For relaxing stiff muscles:

        Adults and teenagers 15 years of age and older-The usual dose is 10 milligrams (mg) three times a day. The largest amount should be no more than 60 mg (six 10-mg tablets) a day.

        Children and teenagers up to 15 years of age-Dose must be determined by your doctor.

Missed dose

If you miss a dose of this medicine and remember within an hour or so of the missed dose, take it right away. Then go back to your regular dosing schedule. But if you do not remember until later, skip the missed dose and go back to your regular dosing schedule. Do not double doses.


To store this medicine:

    • Keep out of the reach of children.

    • Store away from heat and direct light.

    • Do not store this medicine in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.

    • Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.


This medicine will add to the effects of alcohol and other CNS depressants (medicines that slow down the nervous system, possibly causing drowsiness). Some examples of CNS depressants are antihistamines or medicine for hay fever, other allergies, or colds; sedatives, tranquilizers, or sleeping medicine; prescription pain medicine or narcotics; barbiturates; medicine for seizures; other muscle relaxants; or anesthetics, including some dental anesthetics. Check with your doctor before taking any of the above while you are using this medicine .

This medicine may cause some people to have blurred vision or to become drowsy, dizzy, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert and able to see well .

Cyclobenzaprine may cause dryness of the mouth. For temporary relief, use sugarless candy or gum, melt bits of ice in your mouth, or use a saliva substitute. However, if your mouth continues to feel dry for more than 2 weeks, check with your medical doctor or dentist. Continuing dryness of the mouth may increase the chance of dental disease, including tooth decay, gum disease, and fungus infections.

Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

The following side effects may mean that you are having a serious allergic reaction to the medicine. Get emergency help right away if any of them occur :


Changes in the skin color of the face; fast or irregular breathing; large swellings that look like hives on the face, eyelids, mouth, lips, and/or tongue; puffiness or swelling of the eyelids or the area around the eyes; shortness of breath, troubled breathing, tightness in chest, and/or wheezing; skin rash, hives, or itching.

Also, check with your doctor immediately if any of the following side effects occur:



Symptoms of overdose

Convulsions (seizures); drowsiness (severe); dry, hot, flushed skin; fast or irregular heartbeat; hallucinations (seeing, hearing, or feeling things that are not there); increase or decrease in body temperature; troubled breathing; unexplained muscle stiffness; unusual nervousness or restlessness (severe); vomiting (occurring together with other symptoms of overdose).

Also, check with your doctor as soon as possible if any of the following side effects occur:


Clumsiness or unsteadiness; confusion; mental depression or other mood or mental changes; problems in urinating; ringing or buzzing in the ears; skin rash, hives, or itching occurring without other symptoms of an allergic reaction listed above; unusual thoughts or dreams; yellow eyes or skin.

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

More common

Blurred vision; dizziness or lightheadedness; drowsiness; dryness of mouth.

Less common or rare

Bloated feeling or gas, indigestion, nausea or vomiting, or stomach cramps or pain; constipation; diarrhea; excitement or nervousness; frequent urination; general feeling of discomfort or illness; headache; muscle twitching; numbness, tingling, pain, or weakness in hands or feet; pounding heartbeat; problems in speaking; trembling; trouble in sleeping; unpleasant taste or other taste changes; unusual muscle weakness; unusual tiredness.

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.

Additional Information

Once a medicine has been approved for marketing for a certain use, experience may show that it is also useful for other medical problems. Although this use is not included in product labeling, cyclobenzaprine is used in certain patients with fibromyalgia syndrome (also called fibrositis or fibrositis syndrome).

There is no additional information relating to proper use, precautions, or side effects for this use of cyclobenzaprine.

June 03, 1999

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