Medical Editor: John P. Cunha, DO, FACOEP
Amrix (cyclobenzaprine hcl) is a muscle relaxant used together with rest and physical therapy to treat skeletal muscle conditions such as pain or injury. Amrix is available in generic form. Common side effects of Amrix include:
- dry mouth or throat
- blurred vision,
- loss of appetite
- stomach pain
- nausea, or
- muscle weakness
The recommended adult dose for most patients is one Amrix 15 mg capsule taken once daily. Some patients may require up to 30 mg/day, given as one 30 mg capsule taken once daily or as two 15 mg capsules taken once daily. Amrix may interact with MAO inhibitors, atropine, benztropine, dimenhydrinate, methscopolamine, scopolamine, bronchodilators, glycopyrrolate, guanethidine, mepenzolate, tramadol, bladder or urinary medications, or irritable bowel medications. Tell your doctor all medications you use. During pregnancy, Amrix should be used only when prescribed. This medication may pass into breast milk. Consult your doctor before breast-feeding.
Our Amrix (cyclobenzaprine hcl) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.
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.
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Stop using cyclobenzaprine and call your doctor at once if you have any of these serious side effects:
- fast, pounding, or uneven heartbeats;
- chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling;
- sudden numbness or weakness, especially on one side of the body;
- sudden headache, confusion, problems with vision, speech, or balance;
- feeling light-headed, fainting;
- confusion, weakness, lack of coordination;
- nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);
- seizure (convulsions);
- unusual thoughts or behavior, hallucinations (seeing things); or
- easy bruising or bleeding, unusual weakness.
Less serious side effects may include:
- dry mouth or throat;
- blurred vision;
- drowsiness, dizziness, tired feeling;
- loss of appetite, stomach pain, nausea;
- diarrhea, constipation, gas; or
- muscle weakness.
This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.
Read the entire detailed patient monograph for Amrix (Cyclobenzaprine HCl Extended-Release Capsules)
Most Common Adverse Reactions in the AMRIX Clinical Trials
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.
The data described below reflect exposure to AMRIX in 253 patients in 2 clinical trials. AMRIX was studied in two double-blind, parallel-group, placebo-controlled, active-controlled trials of identical design [see Clinical Studies]. The study population was composed of patients with muscle spasms associated with acute painful musculoskeletal conditions. Patients received 15 mg or 30 mg of AMRIX taken orally once daily, cyclobenzaprine immediate-release (IR) 10 mg three times a day, or placebo for 14 days.
Table 1: Incidence of the Most Common Adverse
Reactions Occurring in ≥ 3% of Patients in any Treatment Group* and
Greater Than Placebo in the Two Phase 3, Double-Blind AMRIX Trials
|AMRIX 15 mg
|AMRIX 30 mg
|*AMRIX 15 mg QD, AMRIX 30 mg QD, or cyclobenzaprine IR tablets TID|
Additional Adverse Reactions from Clinical Studies and Postmarketing Experience
The following adverse reactions have been reported in clinical studies or postmarketing experience with AMRIX, cyclobenzaprine IR, or tricyclic drugs. Because some of these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
In a postmarketing surveillance program of cyclobenzaprine IR, the adverse reactions reported most frequently were drowsiness, dry mouth, and dizziness and adverse reactions reported in 1% to 3% of the patients were: fatigue/tiredness, asthenia, nausea, constipation, dyspepsia, unpleasant taste, blurred vision, headache, nervousness, and confusion.
The following adverse reactions have been reported in postmarketing experience (AMRIX or cyclobenzaprine IR), in clinical studies of cyclobenzaprine IR (incidence < 1%), or in postmarketing experience with other tricyclic drugs:
Digestive: Vomiting; anorexia; diarrhea; gastrointestinal pain; gastritis; thirst; flatulence; edema of the tongue; abnormal liver function and rare reports of hepatitis, jaundice, and cholestasis; paralytic ileus, tongue discoloration; stomatitis; parotid swelling.
Endocrine: Inappropriate ADH syndrome.
Metabolic, Nutritional and Immune: Elevation and lowering of blood sugar levels; weight gain or loss.
Musculoskeletal: Local weakness; myalgia.
Nervous System and Psychiatric: Seizures, ataxia; vertigo; dysarthria; tremors; hypertonia; convulsions; muscle twitching; disorientation; insomnia; depressed mood; abnormal sensations; anxiety; agitation; psychosis, abnormal thinking and dreaming; hallucinations; excitement; paresthesia; diplopia; serotonin syndrome; neuroleptic malignant syndrome; decreased or increased libido; abnormal gait; delusions; aggressive behavior; paranoia; peripheral neuropathy; Bell's palsy; alteration in EEG patterns; extrapyramidal symptoms.
Skin: Sweating; photosensitization; alopecia.
Read the entire FDA prescribing information for Amrix (Cyclobenzaprine HCl Extended-Release Capsules)
© Amrix Patient Information is supplied by Cerner Multum, Inc. and Amrix Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.