Generic Name: cyclobenzaprine (sye kloe BEN za preen)
Brand Names: Amrix, Fexmid, Flexeril
Medically reviewed on April 12, 2018
What is Flexeril?
Flexeril (cyclobenzaprine) is a muscle relaxant. It works by blocking nerve impulses (or pain sensations) that are sent to your brain.
Flexeril is used together with rest and physical therapy to treat skeletal muscle conditions such as pain or injury.
Flexeril may also be used for other purposes not listed in this medication guide.
Do not take Flexeril if you have used an MAO inhibitor such as isocarboxazid (Marplan), tranylcypromine (Parnate), phenelzine (Nardil), or selegiline (Eldepryl, Emsam) within the past 14 days. Serious, life-threatening side effects can occur if you take Flexeril before the MAO inhibitor has cleared from your body.
You should not take Flexeril if you have recently had a heart attack, or if you have a heart rhythm disorder, congestive heart failure, heart block, or an overactive thyroid.
Flexeril can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert. Avoid drinking alcohol, which can increase some of the side effects of Flexeril.
Before taking this medicine
Do not take Flexeril if you have used an MAO inhibitor such as isocarboxazid (Marplan), tranylcypromine (Parnate), phenelzine (Nardil), or selegiline (Eldepryl, Emsam) within the past 14 days. Serious, life-threatening side effects can occur if you take Flexeril before the MAO inhibitor has cleared from your body. Do not use Flexeril if you have recently had a heart attack, or if you have:
a heart rhythm disorder;
congestive heart failure;
heart block; or
an overactive thyroid.
Before using Flexeril, tell your doctor if you are allergic to any drugs, or if you have:
problems with urination;
If you have any of these conditions, you may need a dose adjustment or special tests to safely take Flexeril.
FDA pregnancy category B. Flexeril is not expected to be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment. It is not known whether cyclobenzaprine passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.
Older adults may be more sensitive to the side effects of Flexeril.
How should I take Flexeril?
Take this medication exactly as it was prescribed for you. Do not take Flexeril in larger amounts, or take it for longer than recommended by your doctor. Follow the directions on your prescription label.
Take this medicine with a full glass of water.
Flexeril is only part of a complete program of treatment that may also include rest, physical therapy, or other pain relief measures. Follow your doctor's instructions.
Store Flexeril at room temperature away from moisture, heat, and light.
See also: Dosage Information (in more detail)
What happens if I miss a dose?
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at the next regularly scheduled time. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention if you think you have used too much of this medicine. An overdose of Flexeril can be fatal.
Overdose symptoms may include drowsiness, fast heartbeat, tremors or shaking, slurred speech, confusion, nausea, vomiting, hallucinations (seeing things), chest pain, or seizure (convulsions).
What should I avoid?
Flexeril can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert. Avoid drinking alcohol, which can increase some of the side effects of Flexeril. Cold or allergy medicine, narcotic pain medicine, sleeping pills, and medicine for seizures, depression or anxiety can add to sleepiness caused by Flexeril. Tell your doctor if you regularly use any of these medicines, or any other muscle relaxer.
Flexeril side effects
Get emergency medical help if you have any of these signs of an allergic reaction to Flexeril: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Stop using Flexeril 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 Flexeril side effects 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. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
What other drugs will affect Flexeril?
Many drugs can interact with Flexeril. Below is just a partial list. Tell your doctor if you are using:
atropine (Donnatal, and others), benztropine (Cogentin), dimenhydrinate (Dramamine), methscopolamine (Pamine), or scopolamine (Transderm-Scop);
a bronchodilator such as ipratroprium (Atrovent) or tiotropium (Spiriva);
bladder or urinary medications such as darifenacin (Enablex), flavoxate (Urispas), oxybutynin (Ditropan, Oxytrol), tolterodine (Detrol), or solifenacin (Vesicare); or
irritable bowel medications such as dicyclomine (Bentyl), hyoscyamine (Anaspaz, Cystospaz, Levsin, and others), or propantheline (Pro-Banthine).
This list is not complete and there may be other drugs that can interact with Flexeril. Tell your doctor about all your prescription and over-the-counter medications, vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start a new medication without telling your doctor.
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Flexeril only for the indication prescribed.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Copyright 1996-2018 Cerner Multum, Inc. Version: 3.11.
More about Flexeril (cyclobenzaprine)
- Flexeril Side Effects
- During Pregnancy or Breastfeeding
- Dosage Information
- Patient Tips
- Drug Images
- Drug Interactions
- Compare Alternatives
- Support Group
- 139 Reviews
- Drug class: skeletal muscle relaxants