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Amrix Side Effects

Generic name: cyclobenzaprine

Medically reviewed by Drugs.com. Last updated on Oct 16, 2022.

Note: This document contains side effect information about cyclobenzaprine. Some dosage forms listed on this page may not apply to the brand name Amrix.

Applies to cyclobenzaprine: oral capsule extended release, oral suspension, oral tablet.

Serious side effects of Amrix

Along with its needed effects, cyclobenzaprine (the active ingredient contained in Amrix) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking cyclobenzaprine:

Rare

  • Clumsiness or unsteadiness
  • confusion
  • fainting
  • mental depression
  • problems in urinating
  • ringing or buzzing in the ears
  • skin rash, hives, or itching occurring without other symptoms of an allergic reaction listed above
  • unusual thoughts or dreams
  • yellow eyes or skin

Get emergency help immediately if any of the following symptoms of overdose occur while taking cyclobenzaprine:

Symptoms of overdose

  • Convulsions (seizures)
  • drowsiness (severe)
  • dry, hot, flushed skin
  • fast or irregular heartbeat
  • hallucinations (seeing, hearing, or feeling things that are not there)
  • increase or decrease in body temperature
  • troubled breathing
  • unexplained muscle stiffness
  • unusual nervousness or restlessness (severe)
  • vomiting (occurring together with other symptoms of overdose)

Other side effects of Amrix

Some side effects of cyclobenzaprine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Blurred vision
  • dizziness, drowsiness, or lightheadedness
  • dryness of the mouth

Less common or rare

  • Bloated feeling or gas, indigestion, nausea or vomiting, or stomach cramps or pain
  • constipation
  • diarrhea
  • excitement or nervousness
  • frequent urination
  • general feeling of discomfort or illness
  • headache
  • muscle twitching
  • numbness, tingling, pain, or weakness in hands or feet
  • pounding heartbeat
  • problems in speaking
  • trembling
  • trouble sleeping
  • unpleasant taste or other taste changes
  • unusual muscle weakness
  • unusual tiredness

For Healthcare Professionals

Applies to cyclobenzaprine: compounding powder, oral capsule extended release, oral tablet, oral and topical kit.

General

The most frequently occurring adverse reactions have included dry mouth, dizziness, fatigue, constipation, nausea, dyspepsia, and somnolence.[Ref]

Nervous system

Elderly patients may be particularly susceptible to the sedation and confusion which may accompany cyclobenzaprine (the active ingredient contained in Amrix) therapy.[Ref]

Very common (10% or more): Drowsiness (up to 38%)

Common (1% to 10%): Dizziness, somnolence

Postmarketing reports: Headache, serotonin syndrome, seizures, ataxia, tremors, hypertonia, convulsions, abnormal sensations, paresthesia, ageusia[Ref]

Psychiatric

Common (1% to 10%): Irritability, mental acuity decreased, nervousness

Postmarketing reports: Nervousness, confusion, disorientation, insomnia, depressed mood, anxiety, agitation, psychosis, abnormal thinking and dreaming, hallucinations, excitement[Ref]

Hypersensitivity

Postmarketing reports: Anaphylaxis, angioedema, pruritus, facial edema, urticaria, rash[Ref]

Gastrointestinal

Very common (10% or more): Dry mouth (up to 32%)

Common (1% to 10%): Constipation, nausea, dyspepsia, abdominal pain, acid regurgitation, diarrhea

Postmarketing reports: Unpleasant taste, vomiting, anorexia, gastritis, thirst, flatulence, tongue edema[Ref]

Hepatic

Postmarketing reports: Abnormal liver function, hepatitis, jaundice, cholestasis[Ref]

Cardiovascular

Postmarketing reports: Syncope, tachycardia, arrhythmia, vasodilation, palpitation, hypotension[Ref]

Other

Common (1% to 10%): Fatigue

Postmarketing reports: Asthenia, malaise, vertigo[Ref]

Dermatologic

Postmarketing reports: Sweating[Ref]

Genitourinary

Postmarketing reports: Urinary frequency and/or retention[Ref]

Musculoskeletal

Postmarketing reports: Local weakness, dysarthria, muscle twitching[Ref]

Ocular

Postmarketing reports: Blurred vision, diplopia, tinnitus[Ref]

Respiratory

Common (1% to 10%): Upper respiratory infection, pharyngitis[Ref]

Frequently asked questions

References

1. "Product Information. Amrix (cyclobenzaprine)." A-S Medication Solutions (2016):

2. "Product Information. Flexeril (cyclobenzaprine)." Merck & Co., Inc (2001):

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer