Cyclobenzaprine HCL – Uses, Side Effects, and More

This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Cyclobenzaprine

Medically reviewed by Kaci Durbin, MD. Last updated on May 23, 2022.

What is cyclobenzaprine?

Cyclobenzaprine is a muscle relaxant. It works by blocking nerve impulses (or pain sensations) that are sent to your brain. Cyclobenzaprine is used together with rest and physical therapy to treat skeletal muscle conditions such as pain or injury.

Cyclobenzaprine may also be used for purposes not listed in this medication guide.

Warnings

You should not use cyclobenzaprine if you have an allergy to the medication, a certain type of thyroid disorder (hyperthyroidism), heart block, congestive heart failure, a heart rhythm disorder, or you have recently had a heart attack.

Do not use cyclobenzaprine if you have taken an MAO inhibitor in the past 14 days, such as isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, or tranylcypromine.

Before taking this medicine

You should not use cyclobenzaprine if you are allergic to it, or if you have:

• hyperthyroidism;
• heart block, heart rhythm disorder, congestive heart failure; or
• if you have recently had a heart attack.

Cyclobenzaprine is not approved for use by anyone younger than 15 years old.

Do not use cyclobenzaprine if you have taken an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, and tranylcypromine.

Some medicines can interact with cyclobenzaprine and cause a serious condition called serotonin syndrome. Be sure your doctor knows if you also take stimulant medicine, opioid medicine, herbal products, or medicine for depression, mental illness, Parkinson’s disease, migraine headaches, serious infections, or prevention of nausea and vomiting. Ask your doctor before making any changes in how or when you take your medications.

To make sure cyclobenzaprine is safe for you, tell your doctor if you have:

• thyroid disease;
• liver disease;
• glaucoma;
• enlarged prostate; or
• problems with urination.

It is not known whether cyclobenzaprine will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

It may not be safe to breast-feed while using this medicine. Ask your doctor about any risk.

Older adults may be more sensitive to the effects of this medicine.

Related/similar drugs

How should I take cyclobenzaprine?

Cyclobenzaprine is usually taken taken for up to 2 or 3 weeks. Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose.

Follow your doctor’s dosing instructions very carefully.

Swallow the capsule whole and do not crush, chew, break, or open it.

Call your doctor if your symptoms do not improve after 3 weeks, or if they get worse.

Store at room temperature away from moisture, heat, and light.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of cyclobenzaprine can be fatal.

Overdose symptoms may include severe drowsiness, vomiting, fast heartbeats, tremors, agitation, or hallucinations.

What to avoid

Avoid driving or hazardous activity until you know how this medicine will affect you. Your reactions could be impaired.

Avoid drinking alcohol. Dangerous side effects could occur.

Cyclobenzaprine side effects

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.

What other drugs will affect cyclobenzaprine?

Using cyclobenzaprine with other drugs that make you drowsy can worsen this effect. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.

Tell your doctor about all your other medicines, especially:

• MAO inhibitors, such as isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, or tranylcypromine;
• Any antidepressant or anxiety medications;
• bupropion (Zyban, for smoking cessation or Wellbutrin, for depression);
• meperidine;
• tramadol;
• verapamil;
• cold or allergy medicine that contains an antihistamine (Benadryl and others);
• medicine to treat Parkinson’s disease;
• medicine to treat excess stomach acid, stomach ulcer, motion sickness, or irritable bowel syndrome;
• medicine to treat overactive bladder; or
• bronchodilator asthma medication.

This list is not complete. Other drugs may interact with cyclobenzaprine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Where can I get more information?

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use cyclobenzaprine only for the indication prescribed.

Popular FAQ

How long does it take for cyclobenzaprine to work?

Immediate-release cyclobenzaprine tablets work in about 30 to 60 minutes to start relieving your muscle spasm pain. Its duration of action is 4 to 6 hours and it is typically given 3 times per day. It may take up to 7 days for you to see the full therapeutical effect. The extended-release cyclobenzaprine capsules (brand name: Amrix) are usually given once per day but may take longer to start working. Cyclobenzaprine use for periods longer than 2 or 3 weeks is not recommended.

Does cyclobenzaprine make you sleepy?

Yes, cyclobenzaprine can make you very sleepy and this side effect may get worse with higher doses. Drowsiness is the most commonly reported side effect in studies, occurring in up to 38% (38 out of 100) of people. Fatigue and dizziness may also occur. Avoid or limit the use of alcohol or other sedating medicines while being treated with cyclobenzaprine. Also avoid driving, operating machinery, or other hazardous activities until you know how cyclobenzaprine affects you.

For most adults and adolescents 15 years of age and older, the maximum recommended dose of immediate-release cyclobenzaprine tablets is 10 mg three times a day. The maximum adult dose of the extended-release cyclobenzaprine (brand name: Amix) is 30 mg once per day. Always follow your doctor’s dosing instructions. Continue reading

No, cyclobenzaprine is not classified as a controlled substance by the DEA and does not have physically addictive or abuse properties like an opioid or benzodiazepine. It is not an opioid (“narcotic”) drug. However, as with many drugs, some patients may feel psychologically dependent or experience withdrawal symptoms upon discontinuation of cyclobenzaprine. Continue reading

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Cyclobenzaprine HCL – Uses, Side Effects, and More

Cyclobenzaprine is used short-term to treat muscle spasms. It is usually used along with rest and physical therapy. It works by helping to relax the muscles.

How to use cyclobenzaprine oral

Take this medication by mouth with or without food as directed by your doctor. Do not increase your dose or use this drug more often or for longer than prescribed. Your condition will not improve any faster, and your risk of side effects will increase.

The dosage is based on your medical condition and response to treatment. This medication should only be used short-term (for 3 weeks or less) unless directed by your doctor.

Tell your doctor if your condition persists after 2 to 3 weeks or if it worsens.

Side Effects

Drowsiness, dizziness, dry mouth, constipation, or tiredness may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including: fast/irregular heartbeat, mental/mood changes (such as confusion, hallucinations), trouble urinating.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US – Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada – Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Precautions

Before taking cyclobenzaprine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: liver disease, overactive thyroid (hyperthyroidism), heart problems (such as irregular heartbeat, heart block, heart failure, recent heart attack), difficulty urinating (such as due to an enlarged prostate), glaucoma.

This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug, especially drowsiness, confusion, constipation, or trouble urinating. Drowsiness and confusion can increase the risk of falling.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this medication passes into breast milk. However, similar drugs pass into breast milk. Consult your doctor before breast-feeding.

Interactions

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor’s approval.

Some products that may interact with this drug include: tricyclic antidepressants (such as amitriptyline, imipramine).

Taking MAO inhibitors with this medication may cause a serious (possibly fatal) drug interaction. Avoid taking MAO inhibitors (isocarboxazid, linezolid, metaxalone, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, safinamide, selegiline, tranylcypromine) during treatment with this medication. Most MAO inhibitors should also not be taken for two weeks before treatment with this medication. Ask your doctor when to start or stop taking this medication.

Before using this medication, report the use of drugs that increase serotonin, including street drugs (such as MDMA/”ecstasy”), St. John’s wort, certain antidepressants (including SSRIs such as fluoxetine/paroxetine, SNRIs such as duloxetine/venlafaxine), tramadol, among others.

Tell your doctor or pharmacist if you are taking other products that cause drowsiness such as opioid pain or cough relievers (such as codeine, hydrocodone), alcohol, marijuana (cannabis), drugs for sleep or anxiety (such as alprazolam, lorazepam, zolpidem), other muscle relaxants (such as carisoprodol, methocarbamol), or antihistamines (such as cetirizine, diphenhydramine).

Check the labels on all your medicines (such as allergy or cough-and-cold products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those products safely.