Get emergency medical help if you have signs of an allergic reaction to cyclobenzaprine: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Stop using this medicine 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 cyclobenzaprine 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.
 Cyclobenzaprine side effects (more detail)
