Christina Varvatsis is a hospital pharmacist and freelance medical writer committed to educating the public on medication therapy. She strives to promote the safe and effective use of medications.
Additional Content Provided and Reviewed by IBM Micromedex
Amrix (cyclobenzaprine) is a prescription medication used to treat pain and tenderness caused by muscle spasms.
Amrix belongs to a group of medications called skeletal muscle relaxants. These drugs work on receptors in the brain and nervous system, causing your muscles to relax.
Because Amrix is available as an extended-release capsule, you’ll only have to take your dose once per day.
The Food and Drug Administration (FDA) approved Amrix to treat muscle spasms caused by acute musculoskeletal conditions, including low back pain and neck pain.
Healthcare providers often prescribe Amrix after other treatments, such as Advil or Motrin (ibuprofen) or Aleve (naproxen), have failed. Amrix improves pain and tenderness, as well as your ability to move the affected area.
You should use Amrix along with rest and physical therapy, and only take it for short periods—up to two to three weeks.
Take Amrix once a day at the same time each day. Follow your healthcare provider’s instructions for how much to take. Because Amrix comes as an extended-release capsule, be sure to swallow the capsule whole without chewing—this could affect how quickly the medication is released into your body and cause side effects.
Store your Amrix prescription at room temperature in its original container. Keep all your medications in a safe location, out of the reach of children and pets.
Healthcare providers may prescribe medications for off-label uses, meaning not approved for conditions by the FDA.
Off-label conditions Amrix is used to treat include:
Amrix begins to work the first day you start taking it, likely within a few hours. Most people experience the full effects of Amrix after two weeks of treatment.
This is not a complete list of side effects, and others may occur. A medical professional can advise you on side effects. If you experience other effects, contact your pharmacist or a medical professional. You may report side effects to the FDA at www.fda.gov/medwatch or 800-FDA-1088.
As with other medications, Amrix can cause side effects. Talk to your healthcare provider about any side effects you experience.
Watch out for these common side effects, and let your healthcare provider know if they don’t go away:
If you find that Amrix makes you tired, you may want to take your dose at night.
In rare cases, Amrix may cause serious side effects. Call your healthcare provider right away if you think you are experiencing a serious reaction. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency.
Serotonin Syndrome
Rarely, Amrix, when used in combination with certain other drugs, can cause serotonin syndrome. Serotonin syndrome involves a buildup of serotonin (a chemical messenger and key hormone stabilizing mood) in your body and can be life-threatening.
Call your healthcare provider at once if you experience any of the following symptoms:
Heart Problems
Although uncommon, Amrix can affect your heart and lead to heart attack (when blood flow to the heart is blocked) or stroke (when blood flow to the brain is interrupted or reduced). Seek medical care urgently if you experience:
Allergic Reaction
Stop taking Amrix and let your healthcare provider know right away if you develop any signs of an allergic reaction, including:
Amrix may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.
If you experience a serious side effect, you or your provider may send a report to the FDA’s MedWatch Adverse Event Reporting Program or by phone (800-332-1088).
Drug Content Provided and Reviewed by IBM Micromedex
The dose of this medicine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
For relaxing stiff muscles:
For oral dosage form (extended-release capsules):
For oral dosage form (tablets):
If you have difficulty swallowing pills, you’re not alone. Many adults have trouble with this, especially if the capsule is large. Fortunately, Amrix may be opened and sprinkled onto applesauce.
Follow these steps for safely taking your dose:
If you forget to take your dose of Amrix, take it as soon as you remember. If it’s almost time for your next dose, skip the missed dose. Do not double up or take extra. Taking more than your prescribed dose can cause side effects.
Taking more than your recommended dose of Amrix can be dangerous. Overdosing on Amrix can cause serious symptoms, including death. If you or someone else has overdosed on Amrix, it is important to seek medical care immediately since symptoms can progress quickly.
Overdose symptoms include:
If you think you or someone else may have overdosed on Amrix, call a healthcare provider or the Poison Control Center (800-222-1222).
If someone collapses or isn't breathing after taking Amrix, call 911 immediately.
Drug Content Provided and Reviewed by IBM Micromedex
It is very important that your doctor check your progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it.
If your condition does not improve within 2 or 3 weeks, or if it becomes worse, check with your doctor.
Do not use the extended-release capsules if you have used an MAO inhibitor (MAOI) such as Eldepryl®, Marplan®, Nardil®, or Parnate® within 14 days of each other.
Check with your doctor right away if you have anxiety, restlessness, a fast heartbeat, fever, sweating, muscle spasms, twitching, nausea, vomiting, diarrhea, or see or hear things that are not there. These may be symptoms of a serious condition called serotonin syndrome. Your risk may be higher if you also take certain other medicines that affect serotonin levels in your body.
This medicine will add to the effects of alcohol and other CNS depressants (medicines that slow down the nervous system, possibly causing drowsiness). Some examples of CNS depressants are antihistamines or medicine for hay fever, other allergies, or colds, sedatives, tranquilizers, or sleeping medicine, prescription pain medicine or narcotics, medicine for seizures or barbiturates, other muscle relaxants, or anesthetics, including some dental anesthetics. Check with your doctor before taking any of the above while you are using this medicine.
This medicine may cause some people to have blurred vision or to become drowsy, dizzy, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert and able to see well.
Cyclobenzaprine may cause dryness of the mouth. For temporary relief, use sugarless candy or gum, melt bits of ice in your mouth, or use a saliva substitute. However, if your mouth continues to feel dry for more than 2 weeks, check with your medical doctor or dentist. Continuing dryness of the mouth may increase the chance of dental disease, including tooth decay, gum disease, and fungus infections.
Certain conditions increase your risk of developing complications from Amrix. Your healthcare provider will likely recommend a different treatment if any of the following apply to you:
Many drugs may interact with Amrix, including over-the-counter (OTC) nonprescription products. Keep an updated list of all the medicines you take. Share this information with your healthcare providers and pharmacist any time there are changes.
Some common drug interactions to watch for include:
Medications That Increase the Risk of Serotonin Syndrome:
Medications That Increase Sedation (Drowsiness):
Medications That Increase Anticholinergic Side Effects (Dry Mouth, Difficulty Urinating, Blurred Vision, Constipation, and Confusion):
This is not a complete list of all the medications that may interact with Amrix. Always talk to your healthcare provider or pharmacist before starting anything new.
Several other skeletal muscle relaxants are available and work similarly to Amrix. Studies comparing the effectiveness of one muscle relaxant to another are lacking. Amrix only needs to be taken once daily to provide 24-hour relief, unlike other skeletal muscle relaxants.
Other skeletal muscle relaxants include:
This is a list of drugs also prescribed to treat muscle spasms. It is not a list of drugs recommended to take with Amrix. In fact, you should not take these drugs together. Ask your pharmacist or doctor if you have any questions about your medications.
Amrix is used for the short-term treatment of pain associated with musculoskeletal conditions, including back and neck pain. Amrix is often used after NSAIDs (nonsteroidal anti-inflammatory drugs) like ibuprofen or naproxen have failed. Amrix therapy should be combined with rest and physical therapy.
Amrix works by targeting receptors in the brain and nervous system, causing your muscles to relax. Amrix helps improve pain, tenderness, and your ability to move the affected area.
Never take MAOIs with Amrix. These include certain antidepressants and medications used to treat Parkinson’s disease. Do not start Amrix within 14 days of stopping an MAOI. Many other drugs may interact with Amrix. Always talk to your healthcare provider or pharmacist before starting anything new.
The most common side effects of Amrix include constipation, dizziness, drowsiness, dry mouth, fatigue, nausea, and upset stomach. Let your healthcare provider know if any of these symptoms persist or affect your ability to take Amrix.
Let your healthcare provider know if the following conditions apply to you since they can affect your ability to take Amrix safely:
Amrix is generally not recommended for older individuals since they are more likely to develop side effects.
If you’re struggling with muscle pain that won’t go away, Amrix may be able to help—primarily if other treatments like Advil or Motrin or Aleve haven’t worked. It’s important to only take Amrix for the amount of time your healthcare provider has prescribed. The effectiveness and safety of using Amrix long term are unknown.
If your symptoms persist after a few weeks, talk with your provider. Together, you will come up with a plan to get you feeling better and back to doing the things you enjoy.
Verywell Health’s drug information is meant for educational purposes only and not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare professional. Consult your doctor before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.
Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life.
Thank you, {{form.email}}, for signing up.
There was an error. Please try again.
Food and Drug Administration. Amrix label.
Witenko C, Moorman-Li R, Motycka C, et al. Considerations for the appropriate use of skeletal muscle relaxants for the management of acute low back pain. P T. 2014;39(6):427-435.
Macfarlane GJ, Kronisch C, Dean LE, et al. EULAR revised recommendations for the management of fibromyalgia. Ann Rheum Dis. 2017;76(2):318-328. doi:10.1136/annrheumdis-2016-209724
Gauer RL, Semidey MJ. Diagnosis and treatment of temporomandibular. American Family Physician. 2015 Mar 15;91(6):378-386. PMID: 25822556
Foong AL, Patel T, Kellar J, Grindrod KA. The scoop on serotonin syndrome. Can Pharm J (Ott). 2018;151(4):233-239. Published 2018 May 30. doi:10.1177/1715163518779096
Thank you, {{form.email}}, for signing up.
There was an error. Please try again.
Actively scan device characteristics for identification. Use precise geolocation data. Store and/or access information on a device. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners (vendors)