Class: Centrally Acting Skeletal Muscle Relaxants
VA Class: MS200
Chemical Name: 5-[(3,5-Dimethylphenoxy)methyl]-2-oxazolidinone
Molecular Formula: C12H15NO3
CAS Number: 1665-48-1
Brands: Skelaxin
Introduction
Centrally acting skeletal muscle relaxant.b
Uses for Metaxalone
Muscular Conditions
Adjunct to rest, physical therapy, analgesics, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions.101 b
For low back pain, generally reserve skeletal muscle relaxants for adjunctive treatment when pain is unresponsive to OTC analgesics (e.g., NSAIAs).103 104 105 106 107 108
Skeletal muscle relaxants less well tolerated than NSAIAs, and clinical superiority to NSAIAs not established for low back pain.103 104 105 106 107 108
Various skeletal muscle relaxants appear to have comparable efficacy for low back pain relief102 103 and are more effective than placebo.103 105 107
Initially, symptomatic control of acute low back pain focuses on providing sufficient comfort to allow maximum possible activity while awaiting spontaneous recovery; later, as aid to overcome specific activity intolerance.107
Because of rapid spontaneous recovery rate, efficacy of various therapies may be difficult to establish;107 improvement of low back pain usually occurs within 2 weeks, substantial improvement within 4 weeks.106
Ineffective in the treatment of skeletal muscle hyperactivity secondary to chronic neurologic disorders (e.g., cerebral palsy) and other dyskinesias.b
Metaxalone Dosage and Administration
Administration
Oral Administration
Administer orally.101
Manufacturer makes no specific recommendations regarding administration with meals; administration with high-fat meal increases absorption, but clinical importance is unknown.101 (See Food under Pharmacokinetics.)
Dosage
Pediatric Patients
Muscular Conditions
Oral
Children >12 years of age: 800 mg 3 or 4 times daily.101 b
Adults
Muscular Conditions
Oral
800 mg 3 or 4 times daily.101 b
Cautions for Metaxalone
Contraindications
History of drug-induced, hemolytic, or other anemia.101 b
Substantial hepatic or renal impairment.101 b
Known hypersensitivity to metaxalone or any ingredient in the formulation.101 b
Warnings/Precautions
Warnings
CNS Depressants
May enhance the effects of other CNS depressants.101 b (See Specific Drugs and Laboratory Tests under Interactions.)
Sensitivity Reactions
Hypersensitivity Reactions
Possible hypersensitivity reactions.101 b
Specific Populations
Pregnancy
Category B.
Animal studies have failed to reveal fetal risk, but safe use during pregnancy has not been established; do not use in women who are or may become pregnant unless possible benefits outweigh potential risks.101 b
Lactation
Not known whether metaxalone is distributed into milk.101 Use not recommended.101 b
Pediatric Use
Safety and efficacy not established in children ≤12 years of age.101 b
Geriatric Use
Use with caution due to greater frequency of decreased hepatic or renal function and of concomitant disease and drug therapy observed in the elderly.101 b
Hepatic Impairment
Use great caution in patients with a history of liver disease.101 b Perform liver function tests periodically during metaxalone therapy.101 b
Contraindicated in patients with substantial hepatic impairment.101 b
Renal Impairment
Caution advised; contraindicated in patients with substantial renal impairment.101 b
Common Adverse Effects
Drowsiness, dizziness, headache, nervousness or irritability, nausea, vomiting, GI upset.101 b
Interactions for Metaxalone
Specific Drugs and Laboratory Tests
Drug or Test | Interaction | Comments |
|---|---|---|
CNS depressants (e.g., alcohol, barbiturates) | Additive CNS depression101 b | Use caution to avoid overdosage101 b |
Tests for glucose that utilize cupric sulfate (Benedict’s Solution, Clinitest, Fehling’s Solution) | Possible false-positive results101 b | |
Tests for glucose that utilize glucose oxidase (Clinistix, Diastix, Tes-Tape | No interference with test101 b |
Metaxalone Pharmacokinetics
Absorption
Bioavailability
Absolute bioavailability not determined.101
Onset
Usually within 1 hour.b
Duration
About 4–6 hours.b
Food
High-fat meal delays time to peak plasma concentration by about 1–2 hours, increases peak plasma concentration by 178–194%, and increases extent of absorption (AUC) by 115–142%; clinical importance unknown.101
Distribution
Extent
Not known whether metaxalone crosses the placenta or is distributed into milk.101 b
Elimination
Metabolism
Metabolized in the liver.101 b
Elimination Route
Excreted in urine as unidentified metabolites.101 b
Half-life
About 2–4 hours.101 b
Stability
Storage
Oral
Tablets
15–30°C.101 b
ActionsActions
CNS depressant with sedative and skeletal muscle relaxant effects.101 b
Precise mechanism of action is not known; does not directly relax skeletal muscle and has minimal skeletal muscle relaxant effect.101 b Beneficial effect probably is related to sedative properties.101 b
Unlike neuromuscular blocking agents, does not depress neuronal conduction, neuromuscular transmission, or muscle excitability.b
Advice to Patients
Potential for metaxalone to impair mental alertness or physical coordination, especially with concomitant use of alcohol or other CNS depressants; use caution when driving or operating machinery.101 b
Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs and dietary or herbal supplements, as well as concomitant illnesses.101 b
Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.101 b
Importance of informing patients of other important precautionary information. (See Cautions.)
Preparations
Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.
Routes | Dosage Forms | Strengths | Brand Names | Manufacturer |
|---|---|---|---|---|
Oral | Tablets | 800 mg | Skelaxin (scored) | King |
Comparative Pricing
This pricing information is subject to change at the sole discretion of DS Pharmacy. This pricing information was updated 03/2011. Actual costs to patients will vary depending on the use of specific retail or mail-order locations and health insurance copays.
Metaxalone 800MG Tablets (COREPHARMA LLC): 30/$99.99 or 90/$269.96
Skelaxin 800MG Tablets (KING PHARMA): 30/$134.99 or 90/$369.96
Disclaimer
This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.
The American Society of Health-System Pharmacists, Inc. and Drugs.com represent that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. and Drugs.com make no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. and Drugs.com do not endorse or recommend the use of any drug. The information is not a substitute for medical care.
AHFS Drug Information. © Copyright, 1959-2011, Selected Revisions November 2007. American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland 20814.
References
Only references cited for selected revisions after 1984 are available electronically.
101. King Pharmaceuticals, Inc. Skelaxin (metaxalone) tablets prescribing information. Bristol, TN; 2003 Aug.
102. McNeil. Cyclobenzaprine hydrochloride (Flexeril) tablets prescribing information. Fort Washington, PA: 2003 Feb.
103. van Tulder MW, Touray T, Furlan AD et al. Muscle relaxants for non-specific low back pain. The Cochrane Library. From their web site (). Accessed 11/10/2003.
104. van Tulder MW, Scholten RJPM, Kowes BW, et al. Non-steroidal anti-inflammatory drugs for low back pain. The Cochrane Library. From their web site (). Accessed 11/10/2003.
105. Department of Veterans Affairs Veterans Health Administration Office of Quality & Performance. Management of Person with Low Back Pain/Sciatica in Primary Care. From the web site (). Accessed 8/25/2003.
106. Agency for Healthcare Research and Quality. Adult low back pain. From the National Guideline Clearinghouse website. (). Accessed 8/25/2003.
107. U.S. Department of Health and Human Services. Public Health Service. Agency for Halath Care Policy and Research. Acute low back problems in adults. Clinical Practice Guideline.1994; No. 14
108. U.S. Department of Health and Human Services. Public Health Service. Agency for Health Care Policy and Research. Acute low back problems in adults: Assessment and treatment. Clinical Practice Guideline. Quick Reference Guide for Clinicians.1994; No. 14
b. AHFS Drug Information 2006. McEvoy GK, ed. Metaxalone. Bethesda, MD: American Society of Health-System Pharmacists; 2006: 1391-2.
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