What is metaxalone for?



Serotonin syndrome is a potentially life-threatening adverse drug reaction that results from therapeutic drug use, intentional self-poisoning, or inadvertent interactions between drugs . Diagnosis of SS is based on physical exam findings and known exposure to pro-serotonergic medications. The cases presented fulfill the Hunter criteria for diagnosis of SS , and also represent severe SS. The most remarkable physical finding in these cases was extreme rigidity of the lower extremities with sustained spontaneous clonus and flaccid upper extremities. This finding has been reported in SS, and is a helpful physical exam finding for the clinician in diagnosing SS, if present. Inducible, ocular, or spontaneous clonus is a critical element in the diagnosis of serotonin syndrome . A substantial number of drugs and drug combinations have been associated with SS.

Metaxalone is a commonly prescribed “muscle relaxant” without direct muscle relaxing properties and an unknown mechanism of action . Data on metaxalone adverse effects are rare. Death has been reported in overdose but these deaths primarily involved co-ingestants . Forrester reported a series of 142 cases of metaxalone adverse effects. Patients ingesting >2,400 mg (maximal daily dose) were more likely to have pronounced and prolonged symptoms, with three cases developing life-threatening symptoms. The most common adverse effect was lethargy, with other reported findings including: tachycardia, hypertension, muscle rigidity, seizure, mydriasis, diaphoresis, hyperthermia, and coma . Limitations of this study were the absence of reported metaxalone levels, the possibility of co-ingestions, and data limited to poison center charts. However, many of the reported clinical manifestations of metaxalone overdose by Forrester are also seen in SS and in the two cases presented here with confirmed supratherapeutic metaxalone levels. Igneri et al. recently reported a 52-year-old female on citalopram who developed SS after taking a second therapeutic dose of 800-mg metaxalone. Metaxalone levels were not reported in that case. The lack of existing literature associating metaxalone with SS may be related to its unknown mechanism of action, limited side effect profile, under-recognition of SS by healthcare providers, and the limited number of reported overdoses.

Metaxalone, which is 5-(3,5-dimethylphenoxymethyl)-2-oxazolidinone, was first synthesized by Lunsford et al. Oxazolidinone analogs were developed as potential antidepressants and antimicrobial agents. Toloxatone, which is 3-(3-methylphenyl)-5-hydroxymethyl-2-oxaxolidinone, is a reversible monoamine oxidase inhibitor (MAOI) structurally similar to metaxalone . Azoyan et al. reported 122 cases of toloxatone poisoning with severe cases manifesting muscular rigidity and hyperthermia when combined with tricyclic antidepressants, consistent with SS . Linezolid was the first oxazolidinone approved for treatment of gram-positive pathogens and is a reversible MAOI. Co-ingestion of linezolid and pro-serotonergic medications has been associated with the development of SS . Monoamine oxidase inhibitors alone in overdose have produced SS, but are typically associated with SS in combination with other pro-serotonergic medications . We hypothesize, based on its similar structure to known reversible MAO inhibitors, that metaxalone at supratherapeutic concentrations may act as a reversible MAOI like other oxazolidinone analogs. Therefore, metaxalone may be associated with SS alone in overdose (case 2) or in combination with other pro-serotonergic medications (case 1). Monoamine oxidase polymorphism may also be a factor in those developing SS at therapeutic doses versus in overdose or in combination with other pro-serotonergic medications.

Oxazolidinone compounds containing 2-oxazolidinone (box) in the structure. a Metaxalone, b toloxatone, and c linezolid

Tramadol is an agonist at μ-opioid receptors and has been implicated in precipitating SS by its ability to stimulate pre-synaptic release and reuptake inhibition of serotonin . Patients with mydriasis following tramadol overdose are more prone to seizures, and as SS may cause mydriasis; seizures resulting from tramadol overdose may be related to excessive serotonin . The tramadol overdose in case 1 surely contributed to the development of SS, in addition to metaxalone based on the proposed mechanism delineated above. The tramadol overdose in case 1 may have been the primary cause of the witnessed status epilepticus but seizures have also been reported with SS . Both cases demonstrated similar clinical findings with elevated plasma metaxalone levels and a proposed mechanism of action that could lead to increased synaptic serotonin and SS following metaxalone administration. A limitation in case 2 is the absence of GC/MS testing to exclude presence of other pro-serotonergic medications. However, the significantly higher metaxalone level strongly suggests a large ingestion. An empty bottle of metaxalone found at the scene and the patient’s denial of other co-ingestions lend further support to the case. We were unable to determine if metaxalone has other pro-serotonergic properties, such as increasing release or inhibiting reuptake of serotonin, in addition to possible monoamine oxidase inhibition. Further research is required to confirm our hypothesis.

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Generic Name: metaxalone (me TAX a lone)
Brand Name: Skelaxin

Medically reviewed by Drugs.com on Sep 9, 2019 – Written by Cerner Multum

  • Overview
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What is metaxalone?

Metaxalone is a muscle relaxant. It works by blocking nerve impulses (or pain sensations) in the brain.

Metaxalone is used together with rest and physical therapy to treat skeletal muscle conditions such as pain or injury.

Metaxalone may also be used for purposes not listed in this medication guide.

Important Information

You should not use metaxalone if you have anemia (low red blood cells), or severe kidney or liver disease.

Before taking this medicine

You should not use metaxalone if you are allergic to it, or if you have:

  • anemia (low red blood cells);

  • severe kidney disease; or

  • severe liver disease.

To make sure metaxalone is safe for you, tell your doctor if you have liver or kidney disease.

It is not known whether metaxalone will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

It is not known whether metaxalone passes into breast milk or if it could harm a nursing baby. You should not breast-feed while using this medicine.

Metaxalone is not approved for use by anyone younger than 12 years old.

How should I take metaxalone?

Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

This medicine can cause unusual results with certain medical tests. Tell any doctor who treats you that you are using metaxalone.

Metaxalone is only part of a complete treatment program that may also include rest, physical therapy, or other pain relief measures. Follow your doctor’s instructions.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of metaxalone can be fatal.

What should I avoid while taking metaxalone?

Do not drink alcohol. Dangerous side effects or death can occur when alcohol is combined with metaxalone. Check your food and medicine labels to be sure these products do not contain alcohol.

metaxalone may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Dizziness or drowsiness may be more likely in older adults.

Metaxalone side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using metaxalone and call your doctor at once if you have:

  • weak or shallow breathing;

  • a light-headed feeling, like you might pass out;

  • pale or yellowed skin, dark colored urine, fever, confusion or weakness; or

  • upper stomach pain, loss of appetite, jaundice (yellowing of the skin or eyes).

Common side effects may include:

  • dizziness, drowsiness;

  • nausea, vomiting, upset stomach;

  • headache; or

  • feeling nervous or irritable;

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Metaxalone dosing information

Usual Adult Dose for Muscle Spasm:

800 mg orally 3 to 4 times a day

Usual Pediatric Dose for Muscle Spasm:

12 years or older:
800 mg orally 3 to 4 times a day

What other drugs will affect metaxalone?

Taking metaxolone with other drugs that make you sleepy or slow your breathing can cause dangerous or life-threatening side effects. Ask your doctor before taking a sleeping pill, narcotic pain medicine, prescription cough medicine, a muscle relaxer, or medicine for anxiety, depression, or seizures.

Other drugs may interact with metaxalone, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2018 Cerner Multum, Inc. Version: 6.02.

Medical Disclaimer

More about metaxalone

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  • Drug class: skeletal muscle relaxants

Consumer resources

  • Metaxalone
  • Metaxalone (Advanced Reading)

Other brands: Skelaxin, Metaxall

Professional resources

  • Metaxalone (AHFS Monograph)
  • … +2 more

Related treatment guides

  • Muscle Spasm
  • Fibromyalgia



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.

Metaxalone has no direct action on the contractile mechanism of striated muscle, the motor end plate, or the nerve fiber.


The pharmacokinetics of metaxalone have been evaluated in healthy adult volunteers after single dose administration of SKELAXIN under fasted and fed conditions at doses ranging from 400 mg to 800 mg.


Peak plasma concentrations of metaxalone occur approximately 3 hours after a 400 mg oral dose under fasted conditions. Thereafter, metaxalone concentrations decline log-linearly with a terminal half-life of 9.0 ± 4.8 hours. Doubling the dose of SKELAXIN from 400 mg to 800 mg results in a roughly proportional increase in metaxalone exposure as indicated by peak plasma concentrations (Cmax) and area under the curve (AUC). Dose proportionality at doses above 800 mg has not been studied. The absolute bioavailability of metaxalone is not known.

The single-dose pharmacokinetic parameters of metaxalone in two groups of healthy volunteers are shown in Table 1.

Table 1: Mean (%CV) Metaxalone Pharmacokinetic Parameters

Food Effects

A randomized, two-way, crossover study was conducted in 42 healthy volunteers (31 males, 11 females) administered one 400 mg SKELAXIN tablet under fasted conditions and following a standard high-fat breakfast. Subjects ranged in age from 18 to 48 years (mean age = 23.5 ± 5.7 years). Compared to fasted conditions, the presence of a high fat meal at the time of drug administration increased C by 177.5% and increased AUC (AUC0-t, AUC∞) by 123.5% and 115.4%, respectively. Time-to-peak concentration (Tmax) was also delayed (4.3 h versus 3.3 h) and terminal half-life was decreased (2.4 h versus 9.0 h) under fed conditions compared to fasted.

In a second food effect study of similar design, two 400 mg SKELAXIN tablets (800 mg) were administered to healthy volunteers (N=59, 37 males, 22 females), ranging in age from 18-50 years (mean age = 25.6± 8.7 years). Compared to fasted conditions, the presence of a high fat meal at the time of drug administration increased C by 193.6% and increased AUC (AUC0-t , AUC∞) by 146.4% and 142.2%, respectively. Time-to-peak concentration (Tmax) was also delayed (4.9 h versus 3.0 h) and terminal half-life was decreased (4.2 h versus 8.0 h) under fed conditions compared to fasted conditions. Similar food effect results were observed in the above study when one SKELAXIN 800 mg tablet was administered in place of two SKELAXIN 400 mg tablets. The increase in metaxalone exposure coinciding with a reduction in half-life may be attributed to more complete absorption of metaxalone in the presence of a high fat meal (Figure 1).

Figure 1: Mean (SD) Concentrations of Metaxalone following an 800mg Dose under Fasted and Fed Conditions

Distribution, Metabolism, And Excretion

Although plasma protein binding and absolute bioavailability of metaxalone are not known, the apparent volume of distribution (V/F ~ 800 L) and lipophilicity (log P = 2.42) of metaxalone suggest that the drug is extensively distributed in the tissues. Metaxalone is metabolized by the liver and excreted in the urine as unidentified metabolites. Hepatic Cytochrome P450 enzymes play a role in the metabolism of metaxalone. Specifically, CYP1A2, CYP2D6, CYP2E1, and CYP3A4 and, to a lesser extent, CYP2C8, CYP2C9, and CYP2C19 appear to metabolize metaxalone.

Metaxalone does not significantly inhibit major CYP enzymes such as CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4. Metaxalone does not significantly induce major CYP enzymes such as CYP1A2, CYP2B6, and CYP3A4 in vitro.

Pharmacokinetics In Special Populations


The effects of age on the pharmacokinetics of metaxalone were determined following single administration of two 400 mg tablets (800 mg) under fasted and fed conditions. The results were analyzed separately, as well as in combination with the results from three other studies. Using the combined data, the results indicate that the pharmacokinetics of metaxalone are significantly more affected by age under fasted conditions than under fed conditions, with bioavailability under fasted conditions increasing with age.

The bioavailability of metaxalone under fasted and fed conditions in three groups of healthy volunteers of varying age is shown in Table 2.

Table 2: Mean (%CV) Pharmacokinetic Parameters Following Single Administration of Two 400 mg SKELAXIN Tablets (800 mg) under Fasted and Fed Conditions


The effect of gender on the pharmacokinetics of metaxalone was assessed in an open label study, in which 48 healthy adult volunteers (24 males, 24 females) were administered two SKELAXIN 400 mg tablets (800 mg) under fasted conditions. The bioavailability of metaxalone was significantly higher in females compared to males as evidenced by Cmax (2115 ng/mL versus 1335 ng/mL) and AUC∞ (17884 ng·h/mL versus 10328 ng·h/mL). The mean half-life was 11.1 hours in females and 7.6 hours in males. The apparent volume of distribution of metaxalone was approximately 22% higher in males than in females, but not significantly different when adjusted for body weight. Similar findings were also seen when the previously described combined dataset was used in the analysis.

Hepatic/Renal Insufficiency

The impact of hepatic and renal disease on the pharmacokinetics of metaxalone has not been determined. In the absence of such information, SKELAXIN should be used with caution in patients with hepatic and/or renal impairment.


Are you a new drug developer? Contact us to learn more about our customized products and solutions. Stay in the know! As part of our commitment to providing the most up-to-date drug information, we will be releasing #DrugBankUpdates with our newly added curated drug pages. #DrugBankUpdates Name Metaxalone Accession Number DB00660 (APRD00514) Type Small Molecule Groups Approved 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.

Structure 3D Download Similar Structures

Structure for Metaxalone (DB00660)

× Close Synonyms

  • Metassalone
  • Metaxalon
  • Metaxalona
  • Metaxalone
  • Metaxalonum

External IDs AHR 438 Product Images Prescription Products

Name Dosage Strength Route Labeller Marketing Start Marketing End
Unlock Additional Data
Metaxalone Tablet 800 mg/1 Oral St. Marys Medical Park Pharmacy 2011-01-30 2018-11-30 US
Metaxalone Tablet 800 mg/1 Oral Unit Dose Services 2007-11-01 Not applicable US
Metaxalone Tablet 800 mg/1 Oral Stat Rx USA 2007-11-01 Not applicable US
Metaxalone Tablet 800 mg/1 Oral REMEDYREPACK INC. 2018-05-07 Not applicable US
Metaxalone Tablet 800 mg/1 Oral bryant ranch prepack 2007-11-01 2018-05-29 US
Metaxalone Tablet 640 mg/1 Oral Core Pharma, Llc 2015-09-30 2015-09-30 US
Metaxalone Tablet 800 mg/1 Oral Direct Rx 2014-01-01 Not applicable US
Metaxalone Tablet 800 mg/1 Oral Dispensing Solutions, Inc. 2007-11-01 Not applicable US
Metaxalone Tablet 800 mg/1 Oral Amneal Pharmaceuticals of New York Llc 2007-11-01 Not applicable US
Metaxalone Tablet 800 mg/1 Oral Northwind Pharmaceuticals 2014-04-01 Not applicable US

Additional Data Available

  • Application Number Application Number

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

    Learn more

  • Product Code Product Code

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

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Generic Prescription Products

Name Dosage Strength Route Labeller Marketing Start Marketing End
Unlock Additional Data
Metaxall Tablet 800 mg/1 Oral Sircle Laboratories, Llc 2015-09-25 Not applicable US
Metaxalone Tablet 800 mg/1 Oral St. Mary’s Medical Park Pharmacy 2017-12-15 Not applicable US
Metaxalone Tablet 800 mg/1 Oral Major Pharmaceuticals 2017-08-31 Not applicable US
Metaxalone Tablet 800 mg/1 Oral Rebel Distributors 2010-03-31 Not applicable US
Metaxalone Tablet 800 mg/1 Oral A-S Medication Solutions 2013-05-31 Not applicable US
Metaxalone Tablet 800 mg/1 Oral REMEDYREPACK INC. 2019-08-21 Not applicable US
Metaxalone Tablet 800 mg/1 Oral RedPharm Drug, Inc. 2013-05-31 Not applicable US
Metaxalone Tablet 800 mg/1 Oral Clinical Solutions Wholsesale 2013-05-31 2017-06-22 US
Metaxalone Tablet 800 mg/1 Oral REMEDYREPACK INC. 2017-11-02 Not applicable US
Metaxalone Tablet 800 mg/1 Oral bryant ranch prepack 2016-11-22 Not applicable US

Additional Data Available

  • Application Number Application Number

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

    Learn more

  • Product Code Product Code

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

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Mixture Products

Name Ingredients Dosage Route Labeller Marketing Start Marketing End
Lorvatus PharmaPak Metaxalone (800 mg/1) + Diclofenac sodium (16.05 mg/1mL) + Isopropyl alcohol (0.7 mL/1mL) Kit Topical Sircle Laboratories, Llc 2015-12-01 2017-12-31 US

Categories UNII 1NMA9J598Y CAS number 1665-48-1 Weight Average: 221.2524
Monoisotopic: 221.105193351 Chemical Formula C12H15NO3 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



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

Associated Conditions

  • Pain


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.

Unlock Additional Data Additional Data Available Adverse Effects

Comprehensive structured data on known drug adverse effects with statistical prevalence. MedDRA and ICD10 ids are provided for adverse effect conditions and symptoms.

Learn more Additional Data Available Contraindications

Structured data covering drug contraindications. Each contraindication describes a scenario in which the drug is not to be used. Includes restrictions on co-administration, contraindicated populations, and more.

Learn more Additional Data Available Blackbox Warnings

Structured data representing warnings from the black box section of drug labels. These warnings cover important and dangerous risks, contraindications, or adverse effects.

Learn more 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 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


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.

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Drug Interaction
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2,5-Dimethoxy-4-ethylamphetamine The risk or severity of serotonin syndrome can be increased when Metaxalone is combined with 2,5-Dimethoxy-4-ethylamphetamine.
2,5-Dimethoxy-4-ethylthioamphetamine The risk or severity of adverse effects can be increased when Metaxalone is combined with 2,5-Dimethoxy-4-ethylthioamphetamine.
4-Bromo-2,5-dimethoxyamphetamine The risk or severity of adverse effects can be increased when Metaxalone is combined with 4-Bromo-2,5-dimethoxyamphetamine.
4-Methoxyamphetamine The risk or severity of adverse effects can be increased when Metaxalone is combined with 4-Methoxyamphetamine.
5-methoxy-N,N-dimethyltryptamine The risk or severity of adverse effects can be increased when Metaxalone is combined with 5-methoxy-N,N-dimethyltryptamine.
7-Nitroindazole The risk or severity of adverse effects can be increased when Metaxalone is combined with 7-Nitroindazole.
7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline The risk or severity of adverse effects can be increased when Metaxalone is combined with 7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline.
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.

Additional Data Available

  • Extended Description Extended Description

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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

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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 Not Available 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 External Links Human Metabolome Database HMDB0014798 KEGG Drug D00773 KEGG Compound C07934 PubChem Compound 15459 PubChem Substance 46506253 ChemSpider 14709 ChEBI 6797 ChEMBL CHEMBL1079604 PharmGKB PA164747189 RxList RxList Drug Page Drugs.com Drugs.com Drug Page Wikipedia Metaxalone FDA label (124 KB)

Clinical Trials

Clinical Trials

Phase Status Purpose Conditions Count
4 Completed Treatment Back Pain Lower Back 1
Not Available Completed Treatment Knee Osteoarthritis (Knee OA) 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
  • 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

Form Route Strength
Kit 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 tablet

DrugBank does not sell nor buy drugs. Pricing information is supplied for informational purposes only. Patents

Patent Number Pediatric Extension Approved Expires (estimated)
Unlock Additional Data
US6407128 No 2002-06-18 2021-12-03 US
US7122566 No 2006-10-17 2026-02-06 US
US7714006 No 2010-05-11 2021-12-03 US

Additional Data Available

  • Filed On Filed On

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

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State Solid 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

ADMET data is predicted using admetSAR, a free tool for evaluating chemical ADMET properties. (23092397)


Mass Spec (NIST) Not Available Spectra


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 Phenoxy compound / M-xylene / Xylene / Phenol ether / Alkyl aryl ether / Monocyclic benzene moiety / Oxazoline / Ether / Propargyl-type 1,3-dipolar organic compound / Organic 1,3-dipolar compound Molecular Framework Aromatic heteromonocyclic compounds External Descriptors aromatic ether (CHEBI:6797) ×Unlock Data

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Drug created on June 13, 2005 07:24 / Updated on February 02, 2020 00:17

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