AMRIX® (Cyclobenzaprine Hydrochloride Extended-Release Capsules) is a skeletal muscle relaxant which relieves muscle spasm of local origin without interfering with muscle function. The active ingredient in AMRIX extended-release capsules is cyclobenzaprine hydrochloride, USP.
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 two or three 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.
Media Articles Related to Amrix (Cyclobenzaprine)
Source: MedicineNet Dystonia Specialty [2015.01.28]
Title: Muscle Spasms
Category: Diseases and Conditions
Created: 6/16/2009 12:00:00 AM
Last Editorial Review: 1/28/2015 12:00:00 AM
Published Studies Related to Amrix (Cyclobenzaprine)
Evaluation of the muscle relaxant cyclobenzaprine after third-molar extraction. [2011.10]
BACKGROUND: Pain, swelling and trismus are undesirable effects of extraction of impacted mandibular third molars. The authors conducted a study to evaluate the effectiveness of the muscle relaxant cyclobenzaprine when used as a supplement to cryotherapeutic, antibiotic and steroidal anti-inflammatory treatment with the aim of reducing undesirable consequences after third-molar extraction... CONCLUSIONS: The results of this trial indicate that the influence of cyclobenzaprine over pain, swelling and trismus does not justify prescribing additional medication for patients undergoing third-molar extraction. CLINICAL IMPLICATIONS: The muscle relaxant cyclobenzaprine was ineffective in reducing pain, swelling and trismus after third-molar extraction.
Steady-state pharmacokinetics of once-daily cyclobenzaprine extended release: a randomized, double-blind, 2-period crossover study in healthy volunteers. [2011.06]
BACKGROUND: The single-dose pharmacokinetic profile of cyclobenzaprine extended-release (CER) has been previously characterized and compared with the pharmacokinetics of cyclobenzaprine immediate-release (CIR) administered 3 times daily for 3 doses. OBJECTIVE: The objective of this study was to characterize the multiple-dose pharmacokinetic properties of once-daily CER 30 mg and CIR 10 mg TID formulations in healthy volunteers... CONCLUSIONS: Once-daily CER 30 mg delivered sustained plasma cyclobenzaprine levels over 24 hours at steady state. Owing to a protocol violation, steady-state pharmacokinetic properties for CIR could not be assessed. Copyright (c) 2011 Elsevier HS Journals, Inc. All rights reserved.
Evaluation of the muscle relaxant cyclobenzaprine after third-molar extraction. 
aim of reducing undesirable consequences after third-molar extraction... CONCLUSIONS: The results of this trial indicate that the influence of
Steady-state pharmacokinetics of once-daily cyclobenzaprine extended release: a
randomized, double-blind, 2-period crossover study in healthy volunteers. 
in healthy volunteers... CONCLUSIONS: Once-daily CER 30 mg delivered sustained plasma cyclobenzaprine
Efficacy and tolerability of cyclobenzaprine extended release for acute muscle spasm: a pooled analysis. [2010.07]
OBJECTIVE: To assess the efficacy and tolerability of once-daily cyclobenzaprine extended release (CER) 15 and 30 mg in relieving acute muscle spasm... CONCLUSION: Once-daily CER was effective in relieving acute muscle spasm based on patient's rating of medication helpfulness at day 4 and was generally well tolerated with a low rate of reported somnolence.
Clinical Trials Related to Amrix (Cyclobenzaprine)
Efficacy and Safety of Cyclobenzaprine Hydrochloride Extended Release for the Treatment of Chronic Migraine [Recruiting]
The primary objective of the study is to evaluate the effectiveness and safety of
cyclobenzaprine hydrochloride extended release (Amrix 15mg/day) for the prophylaxis of
chronic migraine compared to a placebo medication. A second objective, is to find out
whether there is an improvement in quality of sleep and self-reported depression in patients
taking Amrix 15mg daily. The hypothesis is that the number of migraine days per month of
patients treated with Amrix 15mg daily will be significantly lower than those patients
treated with placebo.
Cyclobenzaprine Extended Release (ER) for Fibromyalgia [Recruiting]
Amrix (Cyclobenzaprine hydrochloride Extended release capsules) is approved by the FDA as a
muscle relaxant, indicated for the treatment of muscle spasm associated with acute, painful
musculoskeletal conditions. Cyclobenzaprine ER (Amrix TM) has a distinct pharmacokinetic
profile providing early systemic exposure and consistent plasma concentration over several
hours. Overall, a single dose of Amrix 30 mg is similar to that of cyclobenzaprine immediate
release 10 mg three times daily. This ER formula should improve compliance, with similar
efficacy and possibly less side effects as is often the case with slower release
There are clinical studies showing that cyclobenzaprine can alleviate pain secondary to
Fibromyalgia induced muscle tone. This multi-layered evidence base suggests that
cyclobenzaprine may be able to alleviate pain in fibromyalgia. Theoretically in
fibromyalgia, pain is interpreted centrally and possibly occurs due to said muscle spasm .
Cyclobenzaprine may relieve this pain, thus allowing patients to function better during the
day and sleep better at night. Cyclobenzaprine has tricyclic antidepressant structure which
may also allow pain signal dampening in the spinal cord as well, similar to amitriptyline
which is used off-label for neuropathic pain as well.
Fibromyalgia (FM) is an illness that may involve medical, rheumatologic, autoimmune, sleep,
endocrine and psychiatric pathology. It is a syndrome of recurrent pain at trigger points.
Greater than 90% of these patients will report fatigue as a key symptom as well. There are
several investigation lines into the treatment of FM induced pain. Exercise, behavioral
therapy, amitryptiline, duloxetine, tramadol, sodium oxybate, pregabalin all have randomized
trials and almost all focus on pain. There are very few studies evaluating cyclobenzaprine
and none studying to Cyclobenzaprine ER formulation. None evaluate pain reduction, sleep
and fatigue improvement.
Cyclobenzaprine is a drug with minimal adverse effects (dry mouth, dizziness, fatigue,
constipation, somnolence, nausea, and dyspepsia). It may have a safer tolerability profile
than some of the FM medications noted above. As cyclobenzaprine is often studied and often
added as an augmentation agent to patients' regimens who suffer from acute painful
musculoskeletal conditions, the authors feel that cyclobenzaprine would also be effective in
this population. The authors wish to conduct a study to determine if cyclobenzaprine ER is
safe and tolerable in the treatment of FM induced pain, and secondary fatigue and insomnia.
This initial study may allow for continued regulatory studies with this product in FM
subjects. The authors propose a double-blind placebo controlled study to determine if
cyclobenzaprine ER is safe and effective in reversing FM induced pain, and secondary fatigue
Use of Cyclobenzaprine After Vaginal Surgery [Recruiting]
The management of post-operative pain in patients after vaginal surgery provides many
unforeseen challenges. Although vaginal surgery is considered a minimally invasive approach
for the repair of pelvic floor prolapse and urinary incontinence, patients may still
experience varying degrees of discomfort and post-operative pain. Narcotics, however, can
introduce a host of problems in addition to the potential addictive properties of the
medication. A vicious cycle ensues as patients seek better pain control at the expense of
worsening constipation, but without adequate control of pain after surgery, voiding
dysfunctions are often exaggerated.
Cyclobenzaprine (Flexeril®) in conjunction with NSAIDs has long been the basis for
management of acute musculoskeletal injuries, but the practice of prescribing this centrally
acting muscle relaxant for post-operative patients has also been successful in the
management of pain.
An online search of medical databases revealed that there are currently no published
retrospective or prospective studies determining the efficacy of cyclobenzaprine in post
surgical patients in conjunction with traditional pain management. The investigators
hypothesize among healthy patients undergoing elective vaginal surgery for pelvic organ
prolapse, the short-term use of a muscle relaxant could reduce the spasticity of the pelvic
floor muscle attributable to surgery and thereby reduce the use of narcotics. Consequently,
the reduction of narcotics and the control of post-surgical pain may also hasten the return
of normal urinary and defecatory function.
Study Comparing A New Drug Containing The Combination Meloxicam And Cyclobenzaprine In The Treatment Of Acute Lumbago [Not yet recruiting]
The purpose of this study is to assess the efficacy end tolerability of a new drug
containing the combination meloxicam and cyclobenzaprine (7,5/10mg) and the same components
alone in the treatment of acute lumbago.
A Randomized Study of Three Medication Regimens for Acute Low Back Pain [Recruiting]
Low back pain causes 2. 4% of visits to US emergency departments (ED) resulting in 2. 7
million visits annually. In a general low back pain (LBP) population, prognosis is poor.
About 50% of patients who visited general practitioners with new onset musculoskeletal LBP
report persistent pain and functional disability three months after the index visit.
Outcomes are similarly poor for the population of patients forced to use an ED for
management of their LBP. In an observational study of patients with non-traumatic LBP
recently completed at the PI's institution, patients were contacted one week after ED
discharge: 70% reported persistent back-pain related functional impairment, 59% reported
moderate or severe LBP, and 69% reported analgesic use within the previous 24 hours. Three
months after the ED visit, 48% reported functional impairment, 42% reported moderate or
severe pain, and 46% reported analgesic use within the previous 24 hours.
A variety of evidence-based medications are available to treat LBP. Non-steroidal
anti-inflammatory drugs (NSAID) are more efficacious than placebo with regard to pain
relief, global improvement, and requirement of analgesic medication. Skeletal
muscle-relaxants too are effective for short-term pain relief and global efficacy. Opioids
are commonly used for moderate or severe acute LBP,(9) though high-quality evidence
supporting this practice is lacking.
Treatment of LBP with multiple concurrent medications is common in the ED setting. Emergency
physicians often prescribe NSAIDs, skeletal muscle relaxants, and opioids in combination.
Several clinical trials have compared combination therapy with NSAIDS+ skeletal muscle
relaxants to monotherapy with just one of these agents. These trials have reported
heterogeneous results. The combination of opioids + NSAIDS has not been evaluated
experimentally in patients with acute LBP.
Given the poor pain and functional outcomes that persist beyond an ED visit for
musculoskeletal LBP, the investigators propose a clinical trial to evaluate whether
combining muscle relaxants or opioids with NSAIDs is more effective than NSAID monotherapy
for the treatment of non-traumatic, non-radicular low back pain. Specifically, the
investigators will evaluate three distinct hypotheses:
1. The combination of naproxen + cyclobenzaprine will provide greater relief of LBP than
naproxen alone seven days after an ED visit, as measured by the Roland Morris low back
pain functional disability scale
2. The combination of naproxen + oxycodone/ acetaminophen will provide greater relief of
LBP than naproxen alone seven days after an ED visit, as measured by the Roland Morris
low back pain functional disability scale
3. The combination of naproxen + oxycodone/ acetaminophen will provide greater relief of
LBP than naproxen + cyclobenzaprine seven days after an ED visit, as measured by the
Roland Morris low back pain functional disability scale
Page last updated: 2015-01-28