Report on Cyclobenzaprine Side Effects and Usage by AskDocWeb


What is Cyclobenzaprine?

Cyclobenzaprine is a muscle relaxant used to treat muscle spasms caused by painful muscle conditions. Typically it is used with rest, physical therapy, and other measures when treating strains, sprains and other muscle injuries. Cyclobenzaprine is also a drug treatment option for fibromyalgia symptoms. It may also be used to treat other conditions (considered off-label use) as determined by your doctor.

Cyclobenzaprine is sold under the brand names Flexeril and Cycloflex. Generic cyclobenzaprine tablets are also available.

Cyclobenzaprine possess some pharmacologic effects similar to tricyclic antidepressants.

How Cyclobenzaprine is used

Cyclobenzaprine comes as a tablet and is taken by mouth. It is usually taken two to four times a day. Do not take this drug for more than 3 weeks without talking to your doctor. Follow the directions on
your prescription label carefully, and ask your doctor or pharmacist to explain anything you don’t
understand. Take cyclobenzaprine exactly as directed. Do not take more or less of it or take it
more often than prescribed by your doctor.

Before taking cyclobenzaprine

Some medical conditions and medications may interact with cyclobenzaprine.
Tell your doctor and pharmacist if you are allergic to any drugs. Be sure to report all prescription and nonprescription drugs (including vitamins) you are taking or have taken within the last 2 weeks, especially medications for

  • depression
  • seizures
  • allergies
  • coughs
  • colds
  • overactive thyroid gland
  • heart disease
  • glaucoma
  • difficulty urinating

Also tell your doctor if you are taking or have taken within the last 14 days

  • MAO inhibitors: phenelzine (Nardil), tranylcypromine (Parnate)
  • sedatives
  • sleeping pills
  • tranquilizers

Tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become
pregnant while taking cyclobenzaprine, call your doctor immediately.

You may need additional monitoring of your dose or condition if you are taking any of the following:

  • Tramadol
  • Droperidol
  • Fluoxetine
  • Rasagiline
  • Anticholinergics (such as Methscopolamine and Benztropine)
  • Barbiturates (such as phenobarbital)
  • Cimetidine
  • Fluconazole
  • Fluvoxamine
  • Mibefradil
  • Naproxen
  • Phenothiazines (such as chlorpromazine)
  • Carbamazepine
  • Guanethidine
  • Guanfacine
  • Phenylephrine

Inform your doctor if you have a history of

  • Liver problems
  • Heart problems
  • Cerebral palsy
  • Brain disease
  • Spinal disease
  • Stroke
  • Glaucoma
  • Trouble urinating

If you miss a dose of Cyclobenzaprine

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose,
skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make
up for the missed one.

Side effects of Cyclobenzaprine

Cyclobenzaprine may cause side effects. Tell your doctor if any of these symptoms are severe or do
not go away:

  • dizziness
  • constipation
  • drowsiness
  • diarrhea
  • fatigue
  • nausea
  • nervousness
  • dry mouth
  • stomach pain
  • upset stomach

If you experience any of the following symptoms, call your doctor immediately:

  • chest pain
  • confusion
  • fainting
  • mental or mood changes
  • numbness of an arm or leg
  • one-sided weakness
  • severe vomiting
  • speech or vision problems
  • trouble urinating
  • yellowing of the eyes or skin
  • difficulty breathing or swallowing
  • fever
  • irregular heart rate
  • seizures
  • severe skin rash
  • swelling of the face or tongue

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug
Administration’s (FDA) MedWatch Adverse Event Reporting program at 1-800-332-1088.

In case of overdose

In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has
collapsed or is not breathing, call local emergency services at 911.

Storing Cyclobenzaprine

Store this medicine at room temperature (not in the bathroom) between 68 and 77 degrees F (20 and 25 degrees C) in a tightly closed container, away from heat, light and children. Throw away any medication that is outdated or no longer needed. Do not flush it down the stool. That causes problems for waste water treatment plants.

General Notes

This drug may make you drowsy. Do not drive a car or operate machinery until you know how cyclobenzaprine affects you.

Alcohol can add to the drowsiness caused by this drug.

Keep all appointments with your doctor.

Cyclobenzaprine may be taken with food if it upsets your stomach.

Do not take Cyclobenzaprine longer than 2 to 3 weeks without checking with your doctor.

Eating grapefruit or drinking grapefruit juice while taking Cyclobenzaprine may increase the amount of this medicine in your blood, which may increase the risk of serious side effects. Talk to your doctor if grapefruit or grapefruit juice is a part of your diet.

Avoid alcohol while taking Cyclobenzaprine. This will add to the effects of alcohol and other depressants.

Avoid becoming overheated in hot weather while taking Cyclobenzaprine; heatstroke may occur.

Caution is advised when using Cyclobenzaprine in the elderly because it may cause confusion, hallucinations, and fast or irregular heartbeat.

For women: If you plan on becoming pregnant, talk to your doctor about the risks and benefits of using Cyclobenzaprine during pregnancy. It is not known if Cyclobenzaprine is excreted in breast milk. Check with your doctor about the risks to your baby.

Cyclobenzaprine is not recommended if you have

  • Overactive thyroid
  • moderate to severe liver problems
  • irregular heartbeat
  • congestive heart failure
  • heart block
  • conduction problems
  • recently had a heart attack

Common Misspellings for Cyclobenzaprine

Cyclobenzaprine is often misspelled, as many people hear the word verbally, write it down and spell it incorrectly. Here are a few of the most common misspellings for Cyclobenzaprine: cyclobenzprine, cyclobenzaprin, cyclobenzapine, cyclobenzaprne, cyclobenaprine, cycobenzaprine, cycobenzaprine, cylobenzaprine, cyclobezaprine, cyclobemzaprine, cyclobenzaprie, cyclbenzaprine, cyclobenzarine, cycloenzaprine, cyclobnzaprine, cclobenzaprine, cyclobenzaprien, and cyclobenzaprnie.

Cyclobenzaprine Feedback

If you’ve used Cyclobenzaprine, please help others by adding your feedback.

Subj: Weight gain?
Date: 12/1/2008
I heard that this medicine can cause weight gain, however, I do not see this as a sideeffect.


AskDocWeb: Both weight gain and weight loss have been reported as rare side effects but a causal relationship has not been established.

Subj: Mentally or physically addictive?
Date: 7/14/2009
Are cyclobenzaprime mentally or physically addictive? Please let me know. Thank you for your help.


AskDocWeb: No, cyclobenzaprine (Amrix) has not been reported to cause mental or physical addiction. There is a caution note about abrupt cessation after prolonged use, in rare cases it may cause nausea, headache, and malaise but these are not indications of addiction.

Subj: Cyclobenzaprine treatment
Date: 11/25/2009
I have used the drug cyclobenzaprine treatment for an arthritic knee and leg. First I was given a shot and then pills… I have extreme pain, left with no appetite lost twenty pounds and have no energy. Would I recommend it? No it has been three weeks and I have not seen any signs of Improving.


Subj: Loss of sex drive
Date: 4/5/2010
I have a total loss of sex drive. Is this a normal side effect?


AskDocWeb: Muscle relaxants such as Cyclobenzaprine (Flexeril) and Orphenadrine (Norflex) have been reported to cause erectile dysfunction in a small percentage of users. If you experience ED and think that it may be a result of your medication, do not stop taking the medication without first consulting your doctor. Other drugs commonly linked to libido loss include:

  • Antidepressants
  • Antihistamines
  • Anti-HIV drugs
  • Blood pressure medications
  • Chemotherapy
  • Finasteride (Propecia)
  • Oral contraceptives (some studies show a link; others don’t)
  • Synthetic progesterone-medroxyprogesterone

If the problem persists, your doctor may be able to prescribe a different medication.

Subj: Helps with muscle strain and sciatica
Date: 5/4/2010
This has helped me with muscle strain and mu sciatica. However it has caused weight gain, and I am not happy about that.


Subj: Weight gain
Date: 6/15/2010
Can you give me the citation where you find Cyclopenzaprine cause weight gain. Thanks,


AskDocWeb: The drug we are talking about here is cyclobenzaprine (Amrix), not Cyclopenzaprine. The reference about possible weight changes comes from the 2010 Physician’s Desk Reference, page 699.

Subj: Contraindications for cyclobenzaprine
Date: 6/16/2010
please anyone have any info about contraindications for a 43 year old woman with cerebral palsy (who has never taken detrol or any such alpha motor neuron inhibitor) to take cyclobenzaprine to forestall spasms so her broken foot bone can heal (it has not been surgically pinned). please answer to thank you.


AskDocWeb: The contraindications listed by the manufacturer for cyclobenzaprine are as follows: “Hypersensitivity to cyclobenzaprine or any component of the formulation; do not use concomitantly or within 14 days of MAO inhibitors; hyperthyroidism; congestive heart failure, arrhythmias, heart block; acute recovery phase of MI”

In the U.S.A. cyclobenzaprine is sold under the brand names of Amrix, Fexmid, and Flexeril. Read more feedback about Cyclobenzaprine.

Most recent post: October 9, 2016

If you find this page useful share it with others. If you have used Cyclobenzaprine, use the form below to add your feedback or review of Cyclobenzaprine. Please note that all addresses are held confidential.