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Side Effects of Cyclobenzaprine (Flexeril)


Description: Flexeril (cyclobenzaprine) is a skeletal muscle relaxant. It works by blocking nerve impulses (or pain sensations) that are sent to your brain. It is most commonly used with rest and physical therapy to treat skeletal muscle conditions such as acute muscle spasms with pain or injury. Flexeril/cyclobenzaprine is typically prescribed to relieve pain from muscle spasms (Flexeril drug label as reported by the U.S. Food and Drug Administration.)

Serious Side Effects

Serious side effects of Flexeril/cyclobenzeprine according to the Flexeril drug label include: fast/irregular heartbeat, mental or mood changes, trouble urinating or fainting. Symptoms of overdose include: convulsions, dry, hot, flushed skin, hallucinations, unexplained muscle stiffness, trouble breathing, severe drowsiness, unusual nervousness, or vomiting.

Common Side Effects

The most common side effects associated with cyclobenzaprine according to the Flexeril drug label are drowsiness, dizziness, dry mouth, constipation or tiredness. Less frequent side effects include: tremor, agitation, coma, ataxia, hypertension, slurred speech, dizziness, confusion, nausea, vomiting and hallucinations.

Less Common Side Effects

According to the Flexeril drug label, rare side effects include:

  • Ringing or buzzing in the ears
  • Skin rash, hives, or itching
  • Unusual thoughts or dreams
  • Yellow eyes or skin
  • Clumsiness or unsteadiness
  • Confusion
  • Fainting
  • Mental depression
  • Problems in urinating
  • Understand Your Risks with the Rxight® Genetic Test

    For the utmost in safety, Rxight® genetic testing from MD Labs offers a panel which examines genes that interact with the medication. Side effects may be lessened by adjusting your dose when your physician has your genetic information from a genetic test

    How Does Pharmacogenetic Testing Work?

    Pharmacogenetic testing – the study of how drugs are metabolized – is a relatively new field that has come of age since the human genome was first completed in the early 2000’s. Every human has a number of genes that are responsible for making enzymes that metabolize medications. The individual gene variability is responsible for differing reactions to medications. Once the test is completed, however, the physician will have at hand the specific information about your ability to metabolize cyclobenzaprine and over 200 medications.



    Contributors to this Article:
    Michael Sapko, MD, PhD; Deborah Kallick, PhD, Medicinal Chemistry


    Read more about Rxight® home DNA testing