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 and topical kit, oral capsule extended release, oral tablet
Get emergency medical help if you have any of these signs of an allergic reaction while taking cyclobenzaprine (the active ingredient contained in Flexeril) 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);
unusual thoughts or behavior, hallucinations (seeing things); or
easy bruising or bleeding, unusual weakness.
Less serious side effects of cyclobenzaprine may include:
dry mouth or throat;
drowsiness, dizziness, tired feeling;
loss of appetite, stomach pain, nausea;
diarrhea, constipation, gas; or
This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.
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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