Medical Editor: John P. Cunha, DO, FACOEP
Flexeril (cyclobenzaprine) is a muscle relaxant indicated as an adjunct to rest and physical therapy for relief of muscle spasm associated with acute, painful musculoskeletal conditions. Common side effects of Flexeril include:
- dry mouth or throat
- blurred vision
- loss of appetite
- stomach pain
- gas, or
- muscle weakness.
For most patients, the recommended dose of Flexeril is 5 mg three times a day.
Flexeril may interact with tricyclic antidepressants, atropine, benztropine, dimenhydrinate, methscopolamine, scopolamine, bronchodilators, glycopyrrolate, guanethidine, mepenzolate, tramadol, bladder or urinary medications, or irritable bowel medications, monoamine oxidase inhibitors (MAOIs), alcohol, barbiturates, and other central nervous system depressants. Tell your doctor all medications and supplements you use. Tell your doctor if you are pregnant or plan to become pregnant during treatment with Flexeril. Flexeril is not expected to be harmful to a fetus. It is unknown if Flexeril passes into breast milk or if it could harm a nursing baby. Consult your doctor before breastfeeding.
Our Flexeril (cyclobenzaprine) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Stop using cyclobenzaprine and call your doctor at once if you have any of these serious side effects:
- fast, pounding, or uneven heartbeats;
- chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling;
- sudden numbness or weakness, especially on one side of the body;
- sudden headache, confusion, problems with vision, speech, or balance;
- feeling light-headed, fainting;
- confusion, weakness, lack of coordination;
- nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);
- seizure (convulsions);
- unusual thoughts or behavior, hallucinations (seeing things); or
- easy bruising or bleeding, unusual weakness.
Less serious side effects may include:
- dry mouth or throat;
- blurred vision;
- drowsiness, dizziness, tired feeling;
- loss of appetite, stomach pain, nausea;
- diarrhea, constipation, gas; or
- muscle weakness.
This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.
Read the entire detailed patient monograph for Flexeril (Cyclobenzaprine Hcl)
Incidence of most common adverse reactions in the 2 double-blind‡, placebo-controlled 5 mg studies (incidence of > 3% on FLEXERIL 5 mg):
|FLEXERIL 5 mg
|FLEXERIL 10 mg
Adverse reactions which were reported in 1% to 3% of the patients were: abdominal pain, acid regurgitation, constipation, diarrhea, dizziness, nausea, irritability, mental acuity decreased, nervousness, upper respiratory infection, and pharyngitis.
The following list of adverse reactions is based on the experience in 473 patients treated with FLEXERIL 10 mg in additional controlled clinical studies, 7607 patients in the post-marketing surveillance program, and reports received since the drug was marketed. The overall incidence of adverse reactions among patients in the surveillance program was less than the incidence in the controlled clinical studies.
The adverse reactions reported most frequently with FLEXERIL were drowsiness, dry mouth and dizziness. The incidence of these common adverse reactions was lower in the surveillance program than in the controlled clinical studies:
‡ Note: FLEXERIL 10 mg data are from one clinical trial. FLEXERIL 5 mg and placebo data are from two studies.
|Clinical Studies With FLEXERIL 10 mg||Surveillance Program With FLEXERIL 10 mg|
Among the less frequent adverse reactions, there was no appreciable difference in incidence in controlled clinical studies or in the surveillance program. Adverse reactions which were reported in 1% to 3% of the patients were: fatigue/tiredness, asthenia, nausea, constipation, dyspepsia, unpleasant taste, blurred vision, headache, nervousness, and confusion.
The following adverse reactions have been reported in post-marketing experience or with an incidence of less than 1% of patients in clinical trials with the 10 mg tablet:
Musculoskeletal: Local weakness.
Nervous System and Psychiatric: Seizures, ataxia; vertigo; dysarthria; tremors; hypertonia; convulsions; muscle twitching; disorientation; insomnia; depressed mood; abnormal sensations; anxiety; agitation; psychosis, abnormal thinking and dreaming; hallucinations; excitement; paresthesia; diplopia.
Urogenital: Urinary frequency and/or retention.
Causal Relationship Unknown
Other reactions, reported rarely for FLEXERIL under circumstances where a causal relationship could not be established or reported for other tricyclic drugs, are listed to serve as alerting information to physicians:
Body as a whole: Chest pain; edema.
Digestive: Paralytic ileus, tongue discoloration; stomatitis; parotid swelling.
Endocrine: Inappropriate ADH syndrome.
Metabolic, Nutritional and Immune: Elevation and lowering of blood sugar levels; weight gain or loss.
Nervous System and Psychiatric: Decreased or increased libido; abnormal gait; delusions; aggressive behavior; paranoia; peripheral neuropathy; Bell's palsy; alteration in EEG patterns; extrapyramidal symptoms.
Skin: Photosensitization; alopecia.
Drug Abuse And Dependence
Pharmacologic similarities among the tricyclic drugs require that certain withdrawal symptoms be considered when FLEXERIL is administered, even though they have not been reported to occur with this drug. Abrupt cessation of treatment after prolonged administration rarely may produce nausea, headache, and malaise. These are not indicative of addiction.
Read the entire FDA prescribing information for Flexeril (Cyclobenzaprine Hcl)
© Flexeril Patient Information is supplied by Cerner Multum, Inc. and Flexeril Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.