Flexeril Side Effects
Generic name: cyclobenzaprine
Note: This document contains side effect information about cyclobenzaprine. Some of the dosage forms listed on this page may not apply to the brand name Flexeril.
Some side effects of Flexeril may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.
For the Consumer
Applies to cyclobenzaprine: oral capsule extended release, oral suspension, oral tablet
Along with its needed effects, cyclobenzaprine (the active ingredient contained in Flexeril) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Stop taking cyclobenzaprine and get emergency help immediately if any of the following effects occur:Rare
- 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
Check with your doctor immediately if any of the following side effects occur while taking cyclobenzaprine:Rare
- 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)
Check with your doctor as soon as possible if any of the following side effects occur while taking cyclobenzaprine:Rare
- Clumsiness or unsteadiness
- 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
Some side effects of cyclobenzaprine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:More common
- Blurred vision
- dizziness or lightheadedness
- dryness of mouth
- Bloated feeling or gas, indigestion, nausea or vomiting, or stomach cramps or pain
- excitement or nervousness
- frequent urination
- general feeling of discomfort or illness
- muscle twitching
- numbness, tingling, pain, or weakness in hands or feet
- pounding heartbeat
- problems in speaking
- trouble in sleeping
- unpleasant taste or other taste changes
- unusual muscle weakness
- unusual tiredness
For Healthcare Professionals
Applies to cyclobenzaprine: compounding powder, oral capsule extended release, oral tablet, oral and topical kit
Elderly patients may be particularly susceptible to the sedation and confusion which may accompany cyclobenzaprine (the active ingredient contained in Flexeril) therapy.
Nervous system side effects are common and include drowsiness in up to 40% of treated patients and dizziness in up to 11%. Fatigue, asthenia, headache, nervousness, blurred vision, and confusion have also been reported.
Other side effects have included anticholinergic effects such as dry mouth (in as many as 27% of treated patients), and, less frequently, dry skin, blurry vision, constipation, and an organic brain syndrome. Paradoxical sweating has also been reported.
Psychiatric side effects including mania and psychosis have been reported rarely. A case of hallucinations has also been reported.
Hypersensitivity side effects have included rash, angioedema, and pruritus. Anaphylaxis has been reported rarely.
Cardiovascular side effects have included cardiac arrhythmias, tachycardia, and hypotension.
More Flexeril resources
- Flexeril Consumer Overview
- Flexeril Prescribing Information (FDA)
- Flexeril Advanced Consumer (Micromedex) - Includes Dosage Information
- Flexeril Monograph (AHFS DI)
- Flexeril MedFacts Consumer Leaflet (Wolters Kluwer)
- Cyclobenzaprine Prescribing Information (FDA)
- Amrix Prescribing Information (FDA)
- Amrix extended-release capsules MedFacts Consumer Leaflet (Wolters Kluwer)
- Fexmid Prescribing Information (FDA)
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