Cyclobenzaprine is a generic drug that’s prescribed for muscle spasms. As with other drugs, cyclobenzaprine can cause side effects, such as drowsiness and anxiety.

Cyclobenzaprine oral tablets are not available in a brand-name version. Cyclobenzaprine oral capsules are available as the brand-name drug Amrix.

Cyclobenzaprine comes as an oral tablet. Cyclobenzaprine also comes in an extended-release oral capsule, but this article does not cover this form.

Read on to learn about potential common, mild, and serious side effects of cyclobenzaprine. For a general overview of the drug, including details about its uses, see this article.

Cyclobenzaprine can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took cyclobenzaprine in clinical trials:

  • drowsiness (See the “Cyclobenzaprine: Side effects specifics” section)
  • dry mouth
  • fatigue
  • headache
  • abdominal pain

Mild side effects can occur with cyclobenzaprine use. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to cyclobenzaprine’s prescribing information.

Mild side effects that have been reported with cyclobenzaprine include:

  • drowsiness*
  • dry mouth
  • fatigue
  • headache
  • abdominal pain
  • acid reflux
  • constipation or diarrhea
  • dizziness
  • nausea
  • anxiety, nervousness, and irritability*

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking cyclobenzaprine and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Cyclobenzaprine: Side effect specifics.”

Cyclobenzaprine may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to cyclobenzaprine’s prescribing information.

If you develop serious side effects while taking cyclobenzaprine, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects that have been reported and their symptoms include:

  • arrhythmia, which may include symptoms such as:
    • heart palpitations (fluttering in your chest)
    • dizziness
  • central nervous system (CNS) depression, which may include symptoms such as:
    • feeling disoriented or confused
    • slurred speech
  • depression, which may include symptoms such as:
    • losing interest in hobbies or activities you typically enjoy
    • difficulty making decisions or concentrating
  • hallucinations (seeing or hearing things that aren’t actually real)
  • psychosis, which may include symptoms such as:
    • hallucinations
    • delusions
  • serotonin syndrome, if cyclobenzaprine is used with certain other medications. Symptoms of serotonin syndrome can include:
    • confusion
    • muscle tremor
ALLERGIC REACTION

For some people, Cyclobenzaprine oral tablet can cause an allergic reaction.

In general, symptoms of allergic reaction can be mild or serious.

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to cyclobenzaprine [form], your doctor may recommend taking a different medication instead.

Cyclobenzaprine may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Does cyclobenzaprine cause weight gain?

It’s not clear whether cyclobenzaprine causes weight gain.

In studies, weight gain was not reported as a side effect by people taking cyclobenzaprine. However, since cyclobenzaprine was approved, both weight gain and weight loss have been reported by people taking the medication. Because these reports happened outside clinical trials, it’s not clear whether weight gain and loss were caused by cyclobenzaprine or another factor.

Cyclobenzaprine is prescribed to relieve muscle spasms related to pain in or injury to your muscles or bones. Muscle spasms, pain, and injury can make it difficult or even impossible to be physically active, which can contribute to weight gain.

Talk with your doctor if you have concerns about your weight or questions about whether medications you take could affect it.

Can cyclobenzaprine cause long-term side effects?

It’s possible. From studies of cyclobenzaprine, it’s not clear whether long-term side effects occurred.

However, some side effects reported in these studies have the potential to last a long time or cause long-term complications. Examples of these side effects include:

  • depression, which may last throughout cyclobenzaprine treatment but may go away once you stop taking it
  • arrhythmia

Talk with your doctor or pharmacist if you have questions about cyclobenzaprine and the potential for long-term side effects.

Learn more about some of the side effects that cyclobenzaprine may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for cyclobenzaprine.

Drowsiness

Drowsiness was the most commonly reported side effect in clinical trials of cyclobenzaprine. This side effect can affect you the next day after taking a dose.

Symptoms of drowsiness include feeling sleepy or tired during the day. This can affect your ability to perform tasks such as driving a vehicle or operating machinery.

Certain factors can increase your risk for drowsiness from taking cyclobenzaprine or make your symptoms severe. These include:

  • consuming alcohol while you’re taking cyclobenzaprine
  • taking other medications that can cause CNS depression, such as opioids or benzodiazepines

What you can do

When you first begin taking cyclobenzaprine, your doctor may advise you to avoid driving, operating machinery, or other similar tasks until you know how taking cyclobenzaprine will affect you.

If you experience drowsiness that bothers you while taking cyclobenzaprine, let your doctor know. They can help determine whether it’s safe for you to continue taking the medication. Cyclobenzaprine is typically used short term, and this side effect should go away once you stop taking cyclobenzaprine.

Anxiety, nervousness, and irritability

Cyclobenzaprine can cause anxiety, nervousness, or irritability as side effects, according to clinical trials of the medication.

Symptoms of anxiety, nervousness, and irritability can include:

  • feeling anxious, nervous, or irritable
  • shaking
  • sweating
  • fast heart rate
  • tension in your muscles

If you have an anxiety disorder, such as generalized anxiety disorder, taking cyclobenzaprine could worsen your symptoms.

What you can do

Contact your doctor if you experience feelings of anxiety, nervousness, or irritability from taking cyclobenzaprine. Your doctor can determine whether you should continue treatment or stop taking cyclobenzaprine. These symptoms should go away once you stop taking cyclobenzaprine.

Since cyclobenzaprine is typically only used short term, your doctor may have you continue taking it if your symptoms are mild. But in this case, they may want to closely monitor you for any signs that your symptoms are worsening.

Below is important information you should consider before taking Cyclobenzaprine.

Precautions

Before taking Cyclobenzaprine, discuss your health history with your doctor. Cyclobenzaprine may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

  • glaucoma, especially angle-closure glaucoma, or any other condition that increases the pressure inside your eye
  • liver condition, such as cirrhosis
  • urinary retention
  • if you are taking or have recently taken a monoamine oxidase inhibitor (MAOI) medication, such as phenelzine (Nardil)
  • previous allergic reaction to this or a similar drug
  • pregnancy
  • breastfeeding
  • alcohol consumption

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.