Flexeril, or cyclobenzaprine, is a muscle relaxant that can help alleviate pain and stiffness caused by muscle spasms. It does, however, have several possible side effects you should be aware of.

If you’re experiencing muscle spasms that are causing pain, your doctor may prescribe a short course of Flexeril 126. This medication is generally effective and safe, but it has a number of possible side effects you should be aware of.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.

What Is Flexeril?

Flexeril is the brand name for cyclobenzaprine, a common muscle relaxant 12. It’s used to reduce muscle spasms that often occur with muscle, ligament or bone injuries. By alleviating these spasms, Flexeril reduces pain and stiffness 12. It’s meant to be used in conjunction with rest and physical therapy.

Flexeril doesn’t act directly on muscles, so it usually doesn’t interfere with normal muscle function or strength 12. It acts primarily in a region of the brain to reduce the likelihood of muscle spasms.

The Flexeril molecule has the same general structure as tricyclic antidepressant medications, such as amitriptyline (Elavil) and imipramine (Tofranil) 126. Because of this, Flexeril has many of the same side effects as these antidepressants 12.

Minor Flexeril Side Effects

  • Drowsiness
  • Dry mouth
  • Dizziness
  • Blurred vision
  • Unpleasant taste in the mouth
  • Loss of appetite
  • Nausea, abdominal pain or indigestion
  • Diarrhea or constipation
  • Nervousness or irritability
  • Confusion
  • Decreased ability to focus mentally :

Serious Flexeril Side Effects

  • Fast, pounding or irregular heartbeat
  • Chest pain
  • Confusion, with weakness or lack of coordination
  • Severe drowsiness
  • Severe nausea
  • Severe abdominal pain
  • Yellowish skin or eyes
  • Seizures
    :

Allergic Reactions and Overdose

  • Severe drowsiness
  • Fast heartbeat
  • High or low blood pressure
  • Vomiting
  • Hallucinations
  • Chest pain
  • Seizures
  • Slurred speech
  • Fever
  • Sweating
  • When severe, coma or death may occur. 
    :

Drug Interactions

  • Medications used to speed up the heartbeat, such as:
  • dicyclomine (Bentyl)
  • hyoscyamine (Anaspaz
  • Cytosplaz)

Contraindications

Because of the possibility of a life-threatening drug interaction — serotonin syndrome — the FDA-approved prescribing information indicates that people who have taken any MAO inhibitor in the past 14 days should not take Flexeril 125. Two weeks are necessary to be certain that no more MAO inhibitor remains in your system.

Because Flexeril may cause a fast or other abnormal heart rhythm, the FDA indicates that it should not be used in people for whom this could be especially dangerous 12. This includes people with a recent heart attack, heart failure, a preexisting abnormal heart rhythm or hyperthyroidism (an overactive thyroid).

Because Flexeril is broken down by the liver, reduced liver function can lead to dangerously high Flexeril levels in the body 12. The FDA recommends taking a lower-than-normal dose if liver function is mildly impaired and completely avoiding Flexeril if liver function is moderately to severely reduced 12.

Additional Warnings

The FDA-approved prescribing information notes that Flexeril should be used for only a short time — for a maximum of two to three weeks 12. This is because there’s no good scientific evidence that it is effective when taken beyond this time.

As well, Flexeril is only approved for use in acute muscle, ligament or bone injuries ,and these conditions should not require a muscle relaxant after three weeks 12.

Flexeril is considered a pregnancy Class B drug 126. This means that it’s most likely safe to take when pregnant, but not enough research has been done to prove that it’s definitely not harmful to the baby. Before taking Flexeril, notify your doctor if you are or could be pregnant 12.

It is unknown whether Flexeril passes into the breast milk, but similar drugs — like the tricyclic antidepressants — do enter it 126. If you are breastfeeding, ask your pediatrician before taking Flexeril 12.

Flexeril can make some conditions worse 12. These include urinary retention (inability to adequately empty the bladder) and glaucoma (raised pressure within the eye). If you have either of these conditions, your doctor may recommend avoiding Flexeril 12.

The combination of alcohol and Flexeril can produce significant drowsiness 126. Do not drink alcohol while taking this medication.

The Wrap Up

As well, Flexeril is only approved for use in acute muscle, ligament or bone injuries ,and these conditions should not require a muscle relaxant after three weeks 12. Avoid driving a car, operating heavy machinery or making important decisions while taking Flexeril, as your ability to think clearly may be impaired 12. Because Flexeril is broken down by the liver, reduced liver function can lead to dangerously high Flexeril levels in the body 12.

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