Physician Resources
Frequently Asked Questions
Click below to view answers to frequently asked questions about AMRIX.
Why AMRIX?
AMRIX is cyclobenzaprine hydrochloride, the country's most widely prescribed skeletal muscle relaxant in a once-daily extended-release formulation. AMRIX is the first and only skeletal muscle relaxant with convenient once-daily dosing.
In clinical trials, AMRIX was significantly better than placebo in patient-rated medication helpfulness at Day 4 and once-daily AMRIX had a discontinuation rate due to somnolence of <2%.
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What is the indication for AMRIX?
AMRIX is indicated as an adjunct to rest and physical therapy for relief of muscle spasm associated with acute, painful musculoskeletal conditions. Improvement is manifested by relief of muscle spasm and its associated signs and symptoms, namely, pain, tenderness, and limitation of motion.
AMRIX should be used only for short periods (up to 2 or 3 weeks) because adequate evidence of effectiveness for more prolonged use is not available and because muscle spasm associated with acute, painful musculoskeletal conditions is generally of short duration and specific therapy for longer periods is seldom warranted.
AMRIX has not been found effective in the treatment of spasticity associated with cerebral or spinal cord disease or in children with cerebral palsy.
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How does AMRIX work?
Cyclobenzaprine relieves skeletal muscle spasm of local origins without interfering with muscle function. Cyclobenzaprine has not been shown to be effective in muscle spasm due to central nervous system disease. In animal models, cyclobenzaprine reduced or abolished skeletal muscle hyperactivity. Animal studies indicate that cyclobenzaprine does not act at the neuromuscular junction or directly on skeletal muscle. Such studies show that cyclobenzaprine acts primarily within the central nervous system at the brain stem as opposed to the spinal cord level, although an overlapping action on the latter may contribute to its overall skeletal muscle relaxant activity. Evidence suggests that the net effect of cyclobenzaprine is a reduction of tonic somatic motor activity, influencing both gamma and alpha motor systems.
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Explain the delivery system of AMRIX?
AMRIX capsules contain extended-release Diffucaps® beads of cyclobenzaprine. Each bead within the capsule is comprised of the following four components: an inert core, one layer of active cyclobenzaprine and two layers of controlled release polymers. The two outer layers control drug diffusion, providing early and sustained release of cyclobenzaprine. This novel formulation of cyclobenzaprine provides AMRIX with its unique pharmacokinetic profile.
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How should AMRIX be taken?
The recommended adult dose for most patients is one (1) AMRIX 15-mg capsule taken once daily. Some patients may require up to 30 mg/day, given as one (1) AMRIX 30-mg capsule taken once daily or as two (2) AMRIX 15-mg capsules taken once daily. It is recommended that doses be taken at approximately the same time each day.
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Is there a specific time of day to take AMRIX?
AMRIX may be taken at any time of day but should be taken at about the same time each day. In clinical trials, AMRIX was administered in the evening between 6 PM and 7 PM. If AMRIX is dosed between 6 PM and 7 PM, as it was in clinical trials, the Tmax should occur around 12 AM to 2 AM.
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What are the side effects of AMRIX therapy?
In clinical trials, the most commonly reported adverse reactions (≥3%) with once-daily AMRIX were dry mouth, dizziness, fatigue, constipation, nausea, and dyspepsia. Less than 5% of patients taking once-daily AMRIX discontinued therapy due to an adverse reaction. AMRIX is closely related to tricyclic antidepressants, which have been reported to produce arrhythmias, sinus tachycardia, prolongation of the conduction time leading to myocardial infarction, and stroke. Because of its atropine-like action, AMRIX should be used with caution in patients with a history of urinary retention, angle-closure glaucoma, increased intraocular pressure, and in patients taking anticholinergic medication.
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Was somnolence reported as an adverse reaction in patients with muscle spasm?
In the two, 14-day clinical efficacy trials, somnolence was reported as an adverse reaction in 1% of patients on AMRIX 15-mg and in 2% of patients on AMRIX 30-mg.
In the clinical trials, less than 2% of patients discontinued therapy due to somnolence.
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Does AMRIX interact with any other drugs?
AMRIX is closely related to the tricyclic antidepressants (e.g., amitriptyline and imipramine) and may have life-threatening interactions with MAO inhibitors. AMRIX may enhance the effects of alcohol, barbiturates, and other CNS depressants. Tricyclic antidepressants may enhance the seizure risk in patients taking tramadol (Ultram® or Ultracet®).
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What patients should not take AMRIX?
AMRIX contraindications:
- Hypersensitivity to any component of this product
- Concomitant use of monoamine oxidase (MAO) inhibitors or within 14 days after their discontinuation
- Hyperpyretic crisis, seizures and death have occurred in patients receiving cyclobenzaprine (or structurally similar tricyclic antidepressants) concomitantly with MAO inhibitor drugs
- During the acute recovery phase of myocardial infarction, and in patients with arrhythmias, heat block conduction disturbances, or congestive heart failure
- Hyperthyroidism
AMRIX should not be used in the elderly or in patients with impaired hepatic function.
The safety and effectiveness of AMRIX has not been studied in pediatric patients. In clinical trials, the youngest age studied was 18.
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How is AMRIX supplied?
AMRIX extended-release capsules are available in 15- and 30-mg strengths. Both dosage strengths are packaged in bottles of 60 capsules. The 15-mg capsules are orange/orange and are embossed in blue ink with "15 mg" on the body, and Cephalon "C" logo, "Cephalon", and a dashed band on the cap. The 30-mg capsules are blue/orange and are embossed in white ink with "30 mg" on the body, and Cephalon "C" logo, "Cephalon", and a dashed band on the cap.
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