- Accession Number
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.
- Small Molecule
- Average: 221.2524
- Chemical Formula
- External IDs
- AHR 438
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.Learn More
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.
The absolute bioavailability of metaxalone from Skelaxin tablets is not known.
- Volume of distribution
- 800 L
- Protein binding
- Not Available
- Route of elimination
Metaxalone is metabolized by the liver and excreted in the urine as unidentified metabolites.
9.2 (+/- 4.8) hours
- 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.Learn More
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
- Not Available
- Pharmacogenomic Effects/ADRs
- Not Available
- 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.
Drug Interaction Abacavir Metaxalone may decrease the excretion rate of Abacavir which could result in a higher serum level. Acarbose Acarbose may decrease the excretion rate of Metaxalone which could result in a higher serum level. Aceclofenac Aceclofenac may decrease the excretion rate of Metaxalone which could result in a higher serum level. Acemetacin Acemetacin may decrease the excretion rate of Metaxalone which could result in a higher serum level. Acetaminophen Acetaminophen may decrease the excretion rate of Metaxalone which could result in a higher serum level. Acetazolamide The risk or severity of adverse effects can be increased when Metaxalone is combined with Acetazolamide. Acetophenazine The risk or severity of adverse effects can be increased when Metaxalone is combined with Acetophenazine. Acetylsalicylic acid Acetylsalicylic acid may decrease the excretion rate of Metaxalone which could result in a higher serum level. Aclidinium Metaxalone may increase the central nervous system depressant (CNS depressant) activities of Aclidinium. Acrivastine Metaxalone may decrease the excretion rate of Acrivastine which could result in a higher serum level.Additional Data Available
- Extended DescriptionExtended Description
Extended description of the mechanism of action and particular properties of each drug interaction.Learn more
A severity rating for each drug interaction, from minor to major.Learn more
- Evidence LevelEvidence Level
A rating for the strength of the evidence supporting each drug interaction.Learn more
An effect category for each drug interaction. Know how this interaction affects the subject drug.Learn more
- 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.
- Product Images
- Brand Name Prescription Products
- Generic Prescription Products
- Mixture Products
Name Ingredients Dosage Route Labeller Marketing Start Marketing End Region Image Lorvatus PharmaPak Metaxalone (800 mg/1) + Diclofenac sodium (16.05 mg/1mL) + Isopropyl alcohol (0.7 mL/1mL) Kit Oral; Topical Sircle Laboratories, Llc 2015-12-01 2017-12-31
- Drug Categories
- Chemical TaxonomyProvided by Classyfire
- 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.
- Organic compounds
- Super 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
- 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)
- CAS number
- InChI Key
- IUPAC Name
- 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
- FDA label
- Download (124 KB)
- Clinical Trials
Phase Status Purpose Conditions Count 4 Completed Treatment Back Pain Lower Back 1 Not Available Completed Treatment Osteoarthritis of the Knee 1
- Sandoz inc
- King pharmaceuticals inc
- Elan Corporation
- 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.
- 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
Form Route Strength Kit Oral; Topical Tablet Oral 640 mg/1 Tablet Oral 800 mg/1 Tablet Oral 400 mg/1
Unit description Cost Unit Metaxalone 800 mg tablet 3.88USD tablet Skelaxin 800 mg tablet 3.84USD tablet Skelaxin 400 mg tablet 0.84USD tabletDrugBank does not sell nor buy drugs. Pricing information is supplied for informational purposes only.
Patent Number Pediatric Extension Approved Expires (estimated) Region US6407128 No 2002-06-18 2021-12-03 US7122566 No 2006-10-17 2026-02-06 US7714006 No 2010-05-11 2021-12-03Additional Data Available
- Filed OnFiled On
The date on which a patent was filed with the relevant government.Learn more
- Experimental Properties
Property Value Source melting point (°C) 122 °C PhysProp logP 2.3 Not Available
- Predicted Properties
Property Value Source Water Solubility 1.28 mg/mL ALOGPS logP 1.63 ALOGPS logP 2.37 ChemAxon logS -2.2 ALOGPS pKa (Strongest Acidic) 13.14 ChemAxon pKa (Strongest Basic) -4.9 ChemAxon Physiological Charge 0 ChemAxon Hydrogen Acceptor Count 2 ChemAxon Hydrogen Donor Count 1 ChemAxon Polar Surface Area 47.56 Å2 ChemAxon Rotatable Bond Count 3 ChemAxon Refractivity 59.32 m3·mol-1 ChemAxon Polarizability 23.74 Å3 ChemAxon Number of Rings 2 ChemAxon Bioavailability 1 ChemAxon Rule of Five Yes ChemAxon Ghose Filter Yes ChemAxon Veber's Rule No ChemAxon MDDR-like Rule No ChemAxon
- Predicted ADMET Features
Property Value Probability Human Intestinal Absorption + 1.0 Blood Brain Barrier + 0.9747 Caco-2 permeable + 0.5076 P-glycoprotein substrate Non-substrate 0.7072 P-glycoprotein inhibitor I Non-inhibitor 0.8309 P-glycoprotein inhibitor II Non-inhibitor 0.906 Renal organic cation transporter Non-inhibitor 0.8464 CYP450 2C9 substrate Non-substrate 0.8154 CYP450 2D6 substrate Non-substrate 0.7182 CYP450 3A4 substrate Non-substrate 0.5649 CYP450 1A2 substrate Inhibitor 0.6863 CYP450 2C9 inhibitor Non-inhibitor 0.7448 CYP450 2D6 inhibitor Non-inhibitor 0.7733 CYP450 2C19 inhibitor Non-inhibitor 0.6471 CYP450 3A4 inhibitor Non-inhibitor 0.911 CYP450 inhibitory promiscuity High CYP Inhibitory Promiscuity 0.797 Ames test Non AMES toxic 0.6074 Carcinogenicity Non-carcinogens 0.9312 Biodegradation Not ready biodegradable 0.9544 Rat acute toxicity 2.4250 LD50, mol/kg Not applicable hERG inhibition (predictor I) Weak inhibitor 0.9319 hERG inhibition (predictor II) Non-inhibitor 0.913
- Mass Spec (NIST)
- Not Available
Drug created on June 13, 2005 07:24 / Updated on June 12, 2020 10:51