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Flexeril Side Effects Center
Medical Editor: Melissa Conrad Stöppler, MD
Flexeril (cyclobenzaprine) is a muscle relaxant. Flexeril is available as a generic drug and is prescribed for the short-term relief of muscle spasms due to musculoskeletal conditions (strains, sprains, and other muscle injuries). The most common side effects of Flexeril may include drowsiness, dry mouth, fatigue, dizziness, and headache.
Flexeril is available as tablets to be taken orally. Flexeril (cyclobenzaprine) is closely related to the tricyclic antidepressants and therefore should not be prescribed with or within two weeks of taking monoamine oxidase (MAO) inhibitor drugs. Flexeril may increase the effects of alcohol, barbiturates, and other central nervous system depressants. There are no adequate studies on the use of Flexeril in pregnant women. It is not known if Flexeril is secreted in milk. However, because Flexeril is related to tricyclic antidepressants and some of these are excreted in breast milk, caution is advised in nursing mothers.
Our Flexeril 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.
What is Patient Information in Detail?
Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.
Flexeril in Detail - Patient Information: Side Effects
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) »
What is Patient Information Overview?
A concise overview of the drug for the patient or caregiver from First DataBank.
Flexeril Overview - Patient Information: Side Effects
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: fast/irregular heartbeat, mental/mood changes (such as confusion, hallucinations), trouble urinating.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
Read the entire patient information overview for Flexeril (Cyclobenzaprine Hcl)»
What is Prescribing information?
The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.
Flexeril FDA Prescribing Information: Side Effects
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 postmarketing 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:
|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, serotonin syndrome.
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) »
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Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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