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Identification
Name Metaxalone
Accession Number DB00660 (APRD00514)
Type small molecule
Groups approved
Description

Metaxalone (marketed by King Pharmaceuticals under the brand name Skelaxin®) is a muscle relaxant used to relax muscles and relieve pain caused by strains, sprains, and other musculoskeletal conditions. Its exact mechanism of action is not known, but it may be due to general central nervous system depression. It is considered to be a moderately strong muscle relaxant, with relatively low incidence of side effects. Skelaxin comes in an 800 mg scored tablet. It previously came in both 400 mg and 800 mg tablets. The 400 mg tablet has been discontinued. Possible side effects include nausea, vomiting, drowsiness and CNS side effects such as dizziness, headache, and irritability.
Structure Thumb
Download: MOL | SDF | SMILES | InChI
Display: 2D Structure | 3D Structure
Synonyms
  • Metassalone [Dcit]
  • Metaxalon
  • Metaxalona [INN-Spanish]
  • Metaxalonum [INN-Latin]
  • Metaxalonum [Latin]
  • Metazalone
  • Metazolone
  • Methaxalonum
  • Methoxolone
Synonyms
Metassalone [Dcit]
Metaxalon
Metaxalona [INN-Spanish]
Metaxalonum [INN-Latin]
Metaxalonum [Latin]
Metazalone
Metazolone
Methaxalonum
Methoxolone
Salts Not Available
Brand names
Name Company
Skelaxin
Zorane
Brand mixtures Not Available
Categories
  • Hypnotics and Sedatives
  • Analgesics
  • Muscle Relaxants, skeletal muscle
CAS number 1665-48-1
Weight Average: 221.2524
Monoisotopic: 221.105193351
Chemical Formula C12H15NO3
InChI Key InChIKey=IMWZZHHPURKASS-UHFFFAOYSA-N
InChI
InChI=1S/C12H15NO3/c1-8-3-9(2)5-10(4-8)15-7-11-6-13-12(14)16-11/h3-5,11H,6-7H2,1-2H3,(H,13,14)
Plain Text
IUPAC Name
5-(3,5-dimethylphenoxymethyl)-1,3-oxazolidin-2-one
SMILES
CC1=CC(OCC2CNC(=O)O2)=CC(C)=C1
Plain Text
Mass Spec Not Available
Taxonomy
Kingdom Organic
Classes
  • Carbamates and Derivatives
  • Phenols and Derivatives
  • Ethers
  • Anisoles
  • Phenyl Esters
Substructures
  • Oxazolidines
  • Carbamates and Derivatives
  • Phenols and Derivatives
  • Ethers
  • Benzene and Derivatives
  • Heterocyclic compounds
  • Aromatic compounds
  • Anisoles
  • Oxazolidinones
  • Phenyl Esters
Pharmacology
Indication For the treatment of painful peripheral musculoskeletal conditions and spasticity from upper motor neuron syndromes.
Pharmacodynamics Metaxalone is a skeletal muscle relaxant indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions. The mode of action of this drug has not been clearly identified, but may be related to its sedative properties. Metaxalone does not directly relax tense skeletal muscles in man.
Mechanism of action The mechanism of action of metaxalone in humans has not been established, but may be due to general central nervous system depression.
Absorption The absolute bioavailability of metaxalone from Skelaxin tablets is not known.
Volume of distribution
  • 800 L
Protein binding Not Available
Metabolism Probably hepatic.
Route of elimination Metaxalone is metabolized by the liver and excreted in the urine as unidentified metabolites.
Half life 9.2 (+/- 4.8) hours
Clearance
  • 68 +/- 50 L/h [Subjects received 1×400mg tablet under fasted conditions]
  • 66 +/- 51 L/h [Subjects received 2×400 mg tablets under fasted conditions]
Toxicity LD50=775mg/kg (Rat, oral); LD50=1690 mg/kg (Mouse, oral). When determining the LD50 in rats and mice, progressive sedation, hypnosis and finally respiratoryfailure were noted as the dosage increased. In dogs, no LD50 could be determined as the higher doses produced an emetic action in 15 to 30 minutes.
Affected organisms
  • Humans and other mammals
Pathways Not Available
Pharmacoeconomics
Manufacturers
  • Sandoz inc
  • King pharmaceuticals inc
  • Elan Corporation
Packagers
Dosage forms
Form Route Strength
Tablet Oral
Prices
Unit description Cost Unit
Metaxalone 800 mg tablet 3.88 USD tablet
Skelaxin 800 mg tablet 3.84 USD tablet
Skelaxin 400 mg tablet 0.84 USD tablet
Patents
Country Patent Number Approved Expires (estimated)
United States 7122566 2006-02-06 2026-02-06
United States 6407128 2001-12-03 2021-12-03
Properties
State solid
Melting point 122 oC
Experimental Properties
Property Value Source
logP 2.3 PhysProp
Predicted Properties
Property Value Source
water solubility 1.28e+00 g/l ALOGPS
logP 1.63 ALOGPS
logP 2.37 ChemAxon Molconvert
logS -2.2 ALOGPS
pKa 0 ChemAxon Molconvert
hydrogen acceptor count 2 ChemAxon Molconvert
hydrogen donor count 1 ChemAxon Molconvert
polar surface area 47.56 ChemAxon Molconvert
rotatable bond count 3 ChemAxon Molconvert
refractivity 59.32 ChemAxon Molconvert
polarizability 23.74 ChemAxon Molconvert
References
Synthesis Reference Not Available
General Reference
  1. See S, Ginzburg R: Choosing a skeletal muscle relaxant. Am Fam Physician. 2008 Aug 1;78(3):365-70. Pubmed
  2. Elenbaas JK: Centrally acting oral skeletal muscle relaxants. Am J Hosp Pharm. 1980 Oct;37(10):1313-23. Pubmed
External Links
Resource Link
KEGG Drug D00773 Link_out
KEGG Compound C07934 Link_out
PubChem Compound 15459 Link_out
PubChem Substance 46506253 Link_out
ChemSpider 14709 Link_out
PharmGKB PA450394 Link_out
RxList http://www.rxlist.com/cgi/generic/metax.htm Link_out
Drugs.com http://www.drugs.com/cdi/metaxalone.html Link_out
Wikipedia http://en.wikipedia.org/wiki/Metaxalone Link_out
ATC Codes Not Available
AHFS Codes Not Available
PDB Entries Not Available
FDA label show (124 KB)
MSDS Not Available
Interactions
Drug Interactions
Drug Interaction
Triprolidine The CNS depressants, Triprolidine and Metaxalone, may increase adverse/toxic effects due to additivity. Monitor for increased CNS depressant effects during concomitant therapy.
Food Interactions Not Available
Comments
Drug created on June 13, 2005 07:24 / Updated on February 14, 2012 11:43