Medical Editor: John P. Cunha, DO, FACOEP
What Is Flexeril?
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.
What Are Side Effects of Flexeril?
Common side effects of Flexeril include:
- dry mouth or throat
- headache
- blurred vision
- drowsiness
- dizziness
- fatigue
- loss of appetite
- stomach pain
- nausea
- diarrhea
- constipation
- gas, or
- muscle weakness.
Dosage for Flexeril
For most patients, the recommended dose of Flexeril is 5 mg three times a day.
What Drugs, Substances, or Supplements Interact with Flexeril?
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.
Flexeril During Pregnancy and Breastfeeding
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.
Additional Information
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.
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Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Stop using cyclobenzaprine and call your doctor at once if you have:
- fast or irregular heartbeats;
- chest pain or pressure, pain spreading to your jaw or shoulder; or
- sudden numbness or weakness (especially on one side of the body), slurred speech, balance problems.
Seek medical attention right away if you have symptoms of serotonin syndrome, such as: agitation, hallucinations, fever, sweating, shivering, fast heart rate, muscle stiffness, twitching, loss of coordination, nausea, vomiting, or diarrhea.
Serious side effects may be more likely in older adults.
Common side effects may include:
- drowsiness, tiredness;
- headache, dizziness;
- dry mouth; or
- upset stomach, nausea, constipation.
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.
QUESTION
Nearly everyone has low back pain at some time during their life. See AnswerSIDE 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 N=464 |
FLEXERIL 10 mg N=249 |
Placebo N=469 |
|
| Drowsiness | 29% | 38% | 10% |
| Dry Mouth | 21% | 32% | 7% |
| Fatigue | 6% | 6% | 3% |
| Headache | 5% | 5% | 8% |
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 | |
| Drowsiness | 39% | 16% |
| Dry Mouth | 27% | 7% |
| Dizziness | 11% | 3% |
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:
Body as a Whole: Syncope; malaise.
Cardiovascular: Tachycardia; arrhythmia; vasodilatation; palpitation; hypotension.
Digestive: Vomiting; anorexia; diarrhea; gastrointestinal pain; gastritis; thirst; flatulence; edema of the tongue; abnormal liver function and rare reports of hepatitis, jaundice and cholestasis.
Hypersensitivity: Anaphylaxis; angioedema; pruritus; facial edema; urticaria; rash.
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.
Skin: Sweating.
Special Senses: Ageusia; tinnitus.
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.
Cardiovascular: Hypertension; myocardial infarction; heart block; stroke.
Digestive: Paralytic ileus, tongue discoloration; stomatitis; parotid swelling.
Endocrine: Inappropriate ADH syndrome.
Hematic and Lymphatic: Purpura; bone marrow depression; leukopenia; eosinophilia; thrombocytopenia.
Metabolic, Nutritional and Immune: Elevation and lowering of blood sugar levels; weight gain or loss.
Musculoskeletal: Myalgia.
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.
Respiratory: Dyspnea.
Skin: Photosensitization; alopecia.
Urogenital: Impaired urination; dilatation of urinary tract; impotence; testicular swelling; gynecomastia; breast enlargement; galactorrhea.
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.
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