Metaxalone

Identification

Name
Metaxalone
Accession Number
DB00660
Description

Metaxalone is a moderate to strong muscle relaxant used in the symptomatic treatment of musculoskeletal pain caused by strains, sprains, and other musculoskeletal conditions. It is marketed by King Pharmaceuticals under the brand name Skelaxin®. Its main mechanism of action is thought to involve general central nervous system depression. Metaxalone is associated with few side effects and is available as a 800 mg scored tablet.

Type
Small Molecule
Groups
Approved
Structure
Thumb
Weight
Average: 221.2524
Monoisotopic: 221.105193351
Chemical Formula
C12H15NO3
Synonyms
  • Metassalone
  • Metaxalon
  • Metaxalona
  • Metaxalone
  • Metaxalonum
External IDs
  • AHR 438

Pharmacology

Indication

For the treatment of painful peripheral musculoskeletal conditions and spasticity from upper motor neuron syndromes.

Associated Conditions
Contraindications & Blackbox Warnings
Learn about our commercial Contraindications & Blackbox Warnings data.
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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]
Adverse Effects
Learn about our commercial Adverse Effects data.
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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. Some adverse events associated with the drug include nausea, vomiting, drowsiness and CNS side effects such as dizziness, headache, and irritability.

Affected organisms
  • Humans and other mammals
Pathways
Not Available
Pharmacogenomic Effects/ADRs
Not Available

Interactions

Drug Interactions
This information should not be interpreted without the help of a healthcare provider. If you believe you are experiencing an interaction, contact a healthcare provider immediately. The absence of an interaction does not necessarily mean no interactions exist.
DrugInteraction
AbacavirMetaxalone may decrease the excretion rate of Abacavir which could result in a higher serum level.
AcarboseAcarbose may decrease the excretion rate of Metaxalone which could result in a higher serum level.
AceclofenacAceclofenac may decrease the excretion rate of Metaxalone which could result in a higher serum level.
AcemetacinAcemetacin may decrease the excretion rate of Metaxalone which could result in a higher serum level.
AcetaminophenAcetaminophen may decrease the excretion rate of Metaxalone which could result in a higher serum level.
AcetazolamideThe risk or severity of adverse effects can be increased when Metaxalone is combined with Acetazolamide.
AcetophenazineThe risk or severity of adverse effects can be increased when Metaxalone is combined with Acetophenazine.
Acetylsalicylic acidAcetylsalicylic acid may decrease the excretion rate of Metaxalone which could result in a higher serum level.
AclidiniumMetaxalone may increase the central nervous system depressant (CNS depressant) activities of Aclidinium.
AcrivastineMetaxalone may decrease the excretion rate of Acrivastine which could result in a higher serum level.
Additional Data Available
  • Extended Description
    Extended Description

    Extended description of the mechanism of action and particular properties of each drug interaction.

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  • Severity
    Severity

    A severity rating for each drug interaction, from minor to major.

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  • Evidence Level
    Evidence Level

    A rating for the strength of the evidence supporting each drug interaction.

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  • Action
    Action

    An effect category for each drug interaction. Know how this interaction affects the subject drug.

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Food Interactions
  • Avoid excessive or chronic alcohol consumption. Alcohol may increase the CNS depressant effects of metaxalone.
  • Take with or without food. The absorption of metaxalone is increased when taken with food, which may increase CNS depression, especially in the elderly.

Products

Product Images
Brand Name Prescription Products
NameDosageStrengthRouteLabellerMarketing StartMarketing EndRegionImage
MetaxaloneTablet800 mg/1OralNorthwind Pharmaceuticals2014-04-01Not applicableUS flag
MetaxaloneTablet800 mg/1OralUnit Dose Services2007-11-012017-12-31US flag50436 302420180913 8702 12k6mne
MetaxaloneTablet800 mg/1Oralbryant ranch prepack2007-11-01Not applicableUS flag63629 276820180913 8702 1nevawj
MetaxaloneTablet800 mg/1OralPD-Rx Pharmaceuticals, Inc.2007-11-012020-04-01US flag64720 0321 10 nlmimage10 6108b0b5
MetaxaloneTablet800 mg/1OralREMEDYREPACK INC.2018-05-072020-05-19US flag
MetaxaloneTablet800 mg/1OralPreferred Pharmaceuticals, Inc.2014-02-142019-10-28US flag68788 989620180907 15195 g4j6vn
MetaxaloneTablet800 mg/1OralStat Rx USA2007-11-01Not applicableUS flag
MetaxaloneTablet800 mg/1OralCorePharma, LLC2007-11-012020-04-01US flag
MetaxaloneTablet800 mg/1OralH.J. Harkins Company2007-11-01Not applicableUS flag
MetaxaloneTablet800 mg/1OralCarilion Materials Management2007-11-01Not applicableUS flag68151 466820180907 15195 vi4v5l
Additional Data Available
  • Application Number
    Application Number

    A unique ID assigned by the FDA when a product is submitted for approval by the labeller.

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  • Product Code
    Product Code

    A governmentally-recognized ID which uniquely identifies the product within its regulatory market.

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Generic Prescription Products
NameDosageStrengthRouteLabellerMarketing StartMarketing EndRegionImage
MetaxallTablet800 mg/1OralSircle Laboratories, Llc2015-09-252019-08-14US flag
MetaxaloneTablet800 mg/1OralCalifornia Pharmaceuticals, Llc2017-08-04Not applicableUS flag
MetaxaloneTablet800 mg/1OralPreferred Pharmaceuticals Inc.2017-10-11Not applicableUS flag
MetaxaloneTablet800 mg/1OralPD-Rx Pharmaceuticals, Inc.2017-08-31Not applicableUS flag
MetaxaloneTablet800 mg/1OralA-S Medication Solutions2013-05-312019-01-31US flag50090 118220180913 8702 16e7j70
MetaxaloneTablet800 mg/1OralSt. Mary's Medical Park Pharmacy2020-03-31Not applicableUS flag
MetaxaloneTablet800 mg/1OralAmneal Pharmaceuticals LLC2013-05-31Not applicableUS flag
MetaxaloneTablet800 mg/1OralDoc Rx2019-04-01Not applicableUS flag
MetaxaloneTablet800 mg/1OralSt. Mary's Medical Park Pharmacy2017-12-15Not applicableUS flag
MetaxaloneTablet800 mg/1OralNorthwind Pharmaceuticals2014-02-12Not applicableUS flag
Additional Data Available
  • Application Number
    Application Number

    A unique ID assigned by the FDA when a product is submitted for approval by the labeller.

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  • Product Code
    Product Code

    A governmentally-recognized ID which uniquely identifies the product within its regulatory market.

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Mixture Products
NameIngredientsDosageRouteLabellerMarketing StartMarketing EndRegionImage
Lorvatus PharmaPakMetaxalone (800 mg/1) + Diclofenac sodium (16.05 mg/1mL) + Isopropyl alcohol (0.7 mL/1mL)KitOral; TopicalSircle Laboratories, Llc2015-12-012017-12-31US flag

Categories

Drug Categories
Chemical TaxonomyProvided by Classyfire
Description
This compound belongs to the class of organic compounds known as phenol ethers. These are aromatic compounds containing an ether group substituted with a benzene ring.
Kingdom
Organic compounds
Super Class
Benzenoids
Class
Phenol ethers
Sub Class
Not Available
Direct Parent
Phenol ethers
Alternative Parents
m-Xylenes / Phenoxy compounds / Alkyl aryl ethers / Oxazolines / Propargyl-type 1,3-dipolar organic compounds / Oxacyclic compounds / Azacyclic compounds / Organopnictogen compounds / Organonitrogen compounds / Hydrocarbon derivatives
Substituents
Alkyl aryl ether / Aromatic heteromonocyclic compound / Azacycle / Ether / Hydrocarbon derivative / M-xylene / Monocyclic benzene moiety / Organic 1,3-dipolar compound / Organic nitrogen compound / Organic oxygen compound
Molecular Framework
Aromatic heteromonocyclic compounds
External Descriptors
aromatic ether (CHEBI:6797)

Chemical Identifiers

UNII
1NMA9J598Y
CAS number
1665-48-1
InChI Key
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)
IUPAC Name
5-(3,5-dimethylphenoxymethyl)-1,3-oxazolidin-2-one
SMILES
CC1=CC(OCC2CNC(=O)O2)=CC(C)=C1

References

Synthesis Reference

Spiridon Spireas, "Bioavailable compositions of metaxalone and processes for producing the same." U.S. Patent US20050276844, issued December 15, 2005.

US20050276844
General References
  1. See S, Ginzburg R: Choosing a skeletal muscle relaxant. Am Fam Physician. 2008 Aug 1;78(3):365-70. [PubMed:18711953]
  2. Elenbaas JK: Centrally acting oral skeletal muscle relaxants. Am J Hosp Pharm. 1980 Oct;37(10):1313-23. [PubMed:6999895]
Human Metabolome Database
HMDB0014798
KEGG Drug
D00773
KEGG Compound
C07934
PubChem Compound
15459
PubChem Substance
46506253
ChemSpider
14709
RxNav
59078
ChEBI
6797
ChEMBL
CHEMBL1079604
PharmGKB
PA164747189
RxList
RxList Drug Page
Drugs.com
Drugs.com Drug Page
Wikipedia
Metaxalone
FDA label
Download (124 KB)

Clinical Trials

Clinical Trials
PhaseStatusPurposeConditionsCount
4CompletedTreatmentBack Pain Lower Back1
Not AvailableCompletedTreatmentOsteoarthritis of the Knee1

Pharmacoeconomics

Manufacturers
  • Sandoz inc
  • King pharmaceuticals inc
  • Elan Corporation
Packagers
  • Amerisource Health Services Corp.
  • Apotheca Inc.
  • A-S Medication Solutions LLC
  • Blenheim Pharmacal
  • Cardinal Health
  • D.M. Graham Laboratories Inc.
  • Direct Dispensing Inc.
  • Dispensing Solutions
  • Diversified Healthcare Services Inc.
  • Eon Labs
  • H.J. Harkins Co. Inc.
  • Innoviant Pharmacy Inc.
  • Keltman Pharmaceuticals Inc.
  • King Pharmaceuticals Inc.
  • Lake Erie Medical and Surgical Supply
  • Liberty Pharmaceuticals
  • Mckesson Corp.
  • Nucare Pharmaceuticals Inc.
  • Par Pharmaceuticals
  • PCA LLC
  • PD-Rx Pharmaceuticals Inc.
  • Pharmedix
  • Physicians Total Care Inc.
  • Preferred Pharmaceuticals Inc.
  • Prescript Pharmaceuticals
  • Rebel Distributors Corp.
  • Redpharm Drug
  • Resource Optimization and Innovation LLC
  • Southwood Pharmaceuticals
  • St Mary's Medical Park Pharmacy
  • Stat Rx Usa
  • West-Ward Pharmaceuticals
Dosage Forms
FormRouteStrength
KitOral; Topical
TabletOral640 mg/1
TabletOral800 mg/1
TabletOral400 mg/1
Prices
Unit descriptionCostUnit
Metaxalone 800 mg tablet3.88USD tablet
Skelaxin 800 mg tablet3.84USD tablet
Skelaxin 400 mg tablet0.84USD tablet
DrugBank does not sell nor buy drugs. Pricing information is supplied for informational purposes only.
Patents
Patent NumberPediatric ExtensionApprovedExpires (estimated)Region
US6407128No2002-06-182021-12-03US flag
US7122566No2006-10-172026-02-06US flag
US7714006No2010-05-112021-12-03US flag
Additional Data Available
  • Filed On
    Filed On

    The date on which a patent was filed with the relevant government.

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Properties

State
Solid
Experimental Properties
PropertyValueSource
melting point (°C)122 °CPhysProp
logP2.3Not Available
Predicted Properties
PropertyValueSource
Water Solubility1.28 mg/mLALOGPS
logP1.63ALOGPS
logP2.37ChemAxon
logS-2.2ALOGPS
pKa (Strongest Acidic)13.14ChemAxon
pKa (Strongest Basic)-4.9ChemAxon
Physiological Charge0ChemAxon
Hydrogen Acceptor Count2ChemAxon
Hydrogen Donor Count1ChemAxon
Polar Surface Area47.56 Å2ChemAxon
Rotatable Bond Count3ChemAxon
Refractivity59.32 m3·mol-1ChemAxon
Polarizability23.74 Å3ChemAxon
Number of Rings2ChemAxon
Bioavailability1ChemAxon
Rule of FiveYesChemAxon
Ghose FilterYesChemAxon
Veber's RuleNoChemAxon
MDDR-like RuleNoChemAxon
Predicted ADMET Features
PropertyValueProbability
Human Intestinal Absorption+1.0
Blood Brain Barrier+0.9747
Caco-2 permeable+0.5076
P-glycoprotein substrateNon-substrate0.7072
P-glycoprotein inhibitor INon-inhibitor0.8309
P-glycoprotein inhibitor IINon-inhibitor0.906
Renal organic cation transporterNon-inhibitor0.8464
CYP450 2C9 substrateNon-substrate0.8154
CYP450 2D6 substrateNon-substrate0.7182
CYP450 3A4 substrateNon-substrate0.5649
CYP450 1A2 substrateInhibitor0.6863
CYP450 2C9 inhibitorNon-inhibitor0.7448
CYP450 2D6 inhibitorNon-inhibitor0.7733
CYP450 2C19 inhibitorNon-inhibitor0.6471
CYP450 3A4 inhibitorNon-inhibitor0.911
CYP450 inhibitory promiscuityHigh CYP Inhibitory Promiscuity0.797
Ames testNon AMES toxic0.6074
CarcinogenicityNon-carcinogens0.9312
BiodegradationNot ready biodegradable0.9544
Rat acute toxicity2.4250 LD50, mol/kg Not applicable
hERG inhibition (predictor I)Weak inhibitor0.9319
hERG inhibition (predictor II)Non-inhibitor0.913
ADMET data is predicted using admetSAR, a free tool for evaluating chemical ADMET properties. (23092397)

Spectra

Mass Spec (NIST)
Not Available
Spectra
SpectrumSpectrum TypeSplash Key
Predicted GC-MS Spectrum - GC-MSPredicted GC-MSNot Available
Predicted MS/MS Spectrum - 10V, Positive (Annotated)Predicted LC-MS/MSNot Available
Predicted MS/MS Spectrum - 20V, Positive (Annotated)Predicted LC-MS/MSNot Available
Predicted MS/MS Spectrum - 40V, Positive (Annotated)Predicted LC-MS/MSNot Available
Predicted MS/MS Spectrum - 10V, Negative (Annotated)Predicted LC-MS/MSNot Available
Predicted MS/MS Spectrum - 20V, Negative (Annotated)Predicted LC-MS/MSNot Available
Predicted MS/MS Spectrum - 40V, Negative (Annotated)Predicted LC-MS/MSNot Available
LC-MS/MS Spectrum - LC-ESI-QFT , negativeLC-MS/MSsplash10-00di-0490000000-964e6b5348bafc1182d9
LC-MS/MS Spectrum - LC-ESI-QFT , negativeLC-MS/MSsplash10-0089-0980000000-2b6e14f3b5e5c19c4e5c
LC-MS/MS Spectrum - LC-ESI-QFT , negativeLC-MS/MSsplash10-001i-0910000000-c8b21539b07eb2e7d34e
LC-MS/MS Spectrum - LC-ESI-QFT , negativeLC-MS/MSsplash10-001i-0900000000-0f09eb181838526daa7c
LC-MS/MS Spectrum - LC-ESI-QFT , negativeLC-MS/MSsplash10-001i-0900000000-018693fc5b6345ee25c5
LC-MS/MS Spectrum - LC-ESI-QFT , negativeLC-MS/MSsplash10-001i-0900000000-921f9f6e188e7466aa4d
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-08fr-4900000000-222616eabf1bcdd48049
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-08fr-6900000000-06981ad91bcbeda7d385
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-0a4i-6900000000-77e22c24cb4c6bbc81a1
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-0a4i-8900000000-54c62bf2b5c1b70898bb
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-0a4i-9700000000-82878fa5fbb78b27ef0b
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-0a4i-9500000000-66f674cba4e44834a425

Drug created on June 13, 2005 07:24 / Updated on June 12, 2020 10:51

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