- Accession Number
- DB00423 (APRD01102)
- Small Molecule
- Approved, Vet approved
Methocarbamol tablets and intramuscular injections are prescription medicines indicated in the United States as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions.Label,9 In Canada, methocarbamol can be sold as an over the counter oral medicine at a lower dose that may be combined with acetaminophen or ibuprofen.10 A combination product with acetylsalicylic acid and codeine is available in Canada by prescription.10
Methocarbamol was FDA approved on 16 July 1957.8
- (RS)-2-hydroxy-3-(2-methoxyphenoxy)propyl carbamate
- Product Images
- Prescription Products
Name Dosage Strength Route Labeller Marketing Start Marketing End Methocarbamol Tablet 750 mg/1 Oral Lannett Company, Inc. 2007-06-19 Not applicable Methocarbamol Tablet 500 mg/1 Oral Lannett Company, Inc. 2007-06-19 Not applicable Methocarbamol Tablet 750 mg/1 Oral Vintage Pharmaceuticals, LLC 2007-09-13 2007-09-13 Methocarbamol Tablet 500 mg/1 Oral Vintage Pharmaceuticals, LLC 2007-09-13 2007-09-13 Methocarbamol Inj 100mg/ml Liquid Intramuscular; Intravenous Univet Pharmaceuticals Ltd. 1988-12-31 Not applicable Methocarbamol Omega Liquid Intramuscular; Intravenous Omega Laboratories Ltd 2003-07-28 Not applicable Robaximol Inj 100mg/ml Liquid Intramuscular; Intravenous Montreal Veterinary Products Inc. 1989-12-31 Not applicable Robaxin Injection, solution 100 mg/1mL Intramuscular; Intravenous Baxter Laboratories 2003-12-22 2014-04-30 Robaxin Tablet, film coated 750 mg/1 Oral Ucb Inc 2003-01-20 2014-10-31 Robaxin Tablet, film coated 500 mg/1 Oral Ucb Inc 2003-01-15 2013-01-17
- Generic Prescription Products
- Over the Counter Products
Name Dosage Strength Route Labeller Marketing Start Marketing End Robaxin Tablet Oral Glaxosmithkline Inc 1958-12-31 Not applicable Robaxin 750 Tablet Oral Glaxosmithkline Inc 1993-12-31 Not applicable
- Mixture Products
Name Ingredients Dosage Route Labeller Marketing Start Marketing End A.S.A. With Methocarbamol Night-time Extra Strength Methocarbamol (400 mg) + Acetylsalicylic acid (500 mg) Tablet Oral Cellchem Pharmaceuticals Inc. Not applicable Not applicable Acetaminophen 325mg + Methocarbamol 400mg Caplets Methocarbamol (400 mg) + Acetaminophen (325 mg) Tablet Oral Marcan Pharmaceuticals Inc Not applicable Not applicable Acetaminophen 500mg + Methocarbamol 400mg Extra Strength Caplets Methocarbamol (400 mg) + Acetaminophen (500 mg) Tablet Oral Marcan Pharmaceuticals Inc Not applicable Not applicable Advil Back Pain Methocarbamol (500 mg) + Ibuprofen (200 mg) Tablet Oral Pfizer Consumer Healthcare A Division Of Pfizer Canada Ulc Not applicable Not applicable Analgesic and Muscle Relaxant Methocarbamol (500 mg) + Ibuprofen (400 mg) Tablet Oral Pharmascience Inc 2012-03-20 Not applicable Analgesic and Muscle Relaxant Caplets Methocarbamol (500 mg) + Ibuprofen (200 mg) Tablet Oral TEVA Canada Limited 2009-11-18 Not applicable Aspirin Backache Methocarbamol (400 mg) + Acetylsalicylic acid (325 mg) Tablet Oral Bayer Not applicable Not applicable Aspirin Night-time Methocarbamol (400 mg) + Acetylsalicylic acid (500 mg) Tablet Oral Bayer Inc Consumer Care 2006-05-24 2010-08-05 Axacet-C1/8 Methocarbamol (400 mg) + Acetaminophen (325 mg) + Codeine phosphate (8 mg) Tablet Oral Technilab Pharma Inc. Not applicable Not applicable Axisal-C1/8 Methocarbamol (400 mg) + Acetylsalicylic acid (325 mg) + Codeine phosphate (8 mg) Tablet Oral Technilab Pharma Inc. Not applicable Not applicable
- International/Other Brands
- Bolaxin (Ying Yuan) / Carbaflex (Paill) / Delaxin / DoloVisan (Dr.Kade Pharmaceutische Fabrik) / Fubaxin (Grape King) / Lumirelax (Juvise) / Metocarbamol (AZ Pharma) / Mioflex (Labinco) / Miorel (Cheminter) / Musxan (Pharmasant) / Ortoton (Recordati) / Rebamol (Winston) / Robaxin-750 (Pfizer) / Robinax (Khandelwal) / Sinaxar (Armofar) / Taspan (Honten)
- Acids, Acyclic
- Benzene Derivatives
- Carbamic Acid Esters
- Central Nervous System Agents
- Central Nervous System Depressants
- Centrally-mediated Muscle Relaxation
- Methyl Ethers
- Muscle Relaxants
- Muscle Relaxants, Centrally Acting Agents
- Musculo-Skeletal System
- Peripheral Nervous System Agents
- Phenyl Ethers
- CAS number
- Average: 241.2405
- Chemical Formula
- InChI Key
- IUPAC Name
- 2-hydroxy-3-(2-methoxyphenoxy)propyl carbamate
Methocarbamol tablets and intramuscular injections are indicated in the United States as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions.Label,9 Oral methocarbamol in America may be given up to 1500mg 4 times daily for 2-3 days.3
In Canada, methocarbamol containing oral formulations are sold over the counter for pain associated with muscle spasm.10 However, if these combination formulations include codeine, they are prescription only.10
- Associated Conditions
Methacarbamol is a skeletal muscle relaxant with an unknown mechanism of action.5 Methacarbamol has been shown to block spinal polysynaptic reflexes, decrease nerve transmission in spinal and supraspinal polysynaptic pathways, and prolong the refractory period of muscle cells.5,4 Methocarbamol does not act as a local anesthetic upon injection.4 In animal studies, methocarbamol also prevents convulsions after electric shock.5
- Mechanism of action
The mechanism of action of methocarbamol is thought to be dependant on its central nervous system depressant activity.3 This action may be mediated through blocking spinal polysynaptic reflexes, decreasing nerve transmission in spinal and supraspinal polysynaptic pathways, and prolonging the refractory period of muscle cells.5,4 Methocarbamol has been found to have no effect on contraction of muscle fibres, motor end plates, or nerve fibres.9
Target Actions Organism NCarbonic anhydrase 1inhibitor Humans
The time to maximum concentration is 1.1 hours for both healthy patients and those on hemodialysis.1 The maximum plasma concentration is 21.3mg/L for healthy patients and 28.7mg/L in hemodialysis patients.1 The area under the curve for healthy patients is 52.5mg/L*hr and 87.1mg/L*hr in hemodialysis patients.1 AUC% based on terminal elimination half life is 2% for healthy patients and 4% for hemodialysis patients.1
Older studies report maximum plasma concentrations in 0.5 hours.2
- Volume of distribution
Volume of distribution data in humans is scarce. In horses, the volume of distribution is 515-942mL/kg at steady state or 724-1130mL/kg.5
- Protein binding
Methocarbamol is 46-50% protein bound in healthy patients and 47.3-48.9% protein bound in hemodialysis patients.1
Methocarbamol is metabolized in the liver by demethylation to 3-(2-hydroxyphenoxy)-1,2-propanediol-1-carbamate or hydroxylation to 3-(4-hydroxy-2-methoxyphenoxy)-1,2-propanediol-1-carbamate.2 Methocarbamol and its metabolites are conjugated through glucuronidation or sulfation.2
- Route of elimination
In humans the majority of the dose is eliminated in the urine.2 In dogs, 88.85% of the dose is eliminated in urine and 2.14% in the feces.2 In rats, 84.5-92.5% of the dose is eliminated in the urine and 0-13.3% is eliminated in the feces.2
- Half life
Overdose of methocarbamol may be associated with alcohol and other central nervous system depressants.Label Patients may experience nausea, drowsiness, blurred vision, hypotension, seizures, and coma.Label Treatment of overdose is generally through airway maintenance, monitoring urinary output, vital signs, and giving fluid intravenously if necessary.Label
The oral LD50 in rats is 3576.2mg/kg.10
The FDA has classified methocarbamol as pregnancy category C.Label Animal and human studies have not been performed to determine the risks to a fetus, however fetal and congenital abnormalities have been reported.Label Methocarbamol is excreted in the milk of dogs, however it is unknown if this is also the case for humans.Label Caution should be exercised when taking methocarbamol while breastfeeding.Label
Studies to assess the carcinogenicity, mutagenicity, or effects on fertility of methocarbamol have not been performed.Label
- Affected organisms
- Humans and other mammals
- Not Available
- Pharmacogenomic Effects/ADRs
- Not Available
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
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
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
- 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 2,5-Dimethoxy-4-ethylthioamphetamine The risk or severity of adverse effects can be increased when Methocarbamol is combined with 2,5-Dimethoxy-4-ethylthioamphetamine. 4-Bromo-2,5-dimethoxyamphetamine The risk or severity of adverse effects can be increased when Methocarbamol is combined with 4-Bromo-2,5-dimethoxyamphetamine. 4-Methoxyamphetamine The risk or severity of adverse effects can be increased when Methocarbamol is combined with 4-Methoxyamphetamine. 5-methoxy-N,N-dimethyltryptamine The risk or severity of adverse effects can be increased when Methocarbamol is combined with 5-methoxy-N,N-dimethyltryptamine. 7-Nitroindazole The risk or severity of adverse effects can be increased when Methocarbamol is combined with 7-Nitroindazole. 7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline The risk or severity of adverse effects can be increased when Methocarbamol is combined with 7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline. Acepromazine The risk or severity of adverse effects can be increased when Methocarbamol is combined with Acepromazine. Aceprometazine The risk or severity of adverse effects can be increased when Methocarbamol is combined with Aceprometazine. Acetazolamide The risk or severity of adverse effects can be increased when Methocarbamol is combined with Acetazolamide. Acetophenazine The risk or severity of adverse effects can be increased when Methocarbamol is combined with Acetophenazine.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 alcohol.
- Take with or without food. The absorption is unaffected by food.
- General References
- Sica DA, Comstock TJ, Davis J, Manning L, Powell R, Melikian A, Wright G: Pharmacokinetics and protein binding of methocarbamol in renal insufficiency and normals. Eur J Clin Pharmacol. 1990;39(2):193-4. [PubMed:2253675]
- Bruce RB, Turnbull LB, Newman JH: Metabolism of methocarbamol in the rat, dog, and human. J Pharm Sci. 1971 Jan;60(1):104-6. [PubMed:5548215]
- Witenko C, Moorman-Li R, Motycka C, Duane K, Hincapie-Castillo J, Leonard P, Valaer C: Considerations for the appropriate use of skeletal muscle relaxants for the management of acute low back pain. P T. 2014 Jun;39(6):427-35. [PubMed:25050056]
- Crankshaw DP, Raper C: Mephenesin, methocarbamol, chlordiazepoxide and diazepam: actions on spinal reflexes and ventral root potentials. Br J Pharmacol. 1970 Jan;38(1):148-56. doi: 10.1111/j.1476-5381.1970.tb10343.x. [PubMed:5413283]
- Muir WW 3rd, Sams RA, Ashcraft S: The pharmacology and pharmacokinetics of high-dose methocarbamol in horses. Equine Vet J Suppl. 1992 Feb;(11):41-4. [PubMed:9109959]
- Authors unspecified: Methocarbamol-A New Lissive Agent. Can Med Assoc J. 1958 Dec 15;79(12):1008-9. [PubMed:20325834]
- O'DOHERTY DS, SHIELDS CD: Methocarbamol; new agent in treatment of neurological and neuromuscular diseases. J Am Med Assoc. 1958 May 10;167(2):160-3. [PubMed:13538683]
- FDA Approved Drug Products: Robaxin [Link]
- FDA Approved Drug Products: Robaxin Intramuscular Injection [Link]
- Pfizer Canada: Robax [Link]
- External Links
- ATC Codes
- M03BA73 — Methocarbamol, combinations with psycholeptics
- M03BA — Carbamic acid esters
- M03B — MUSCLE RELAXANTS, CENTRALLY ACTING AGENTS
- M03 — MUSCLE RELAXANTS
- M — MUSCULO-SKELETAL SYSTEM
- M03BA — Carbamic acid esters
- M03B — MUSCLE RELAXANTS, CENTRALLY ACTING AGENTS
- M03 — MUSCLE RELAXANTS
- M — MUSCULO-SKELETAL SYSTEM
- AHFS Codes
- 12:20.04 — Centrally Acting Skeletal Muscle Relaxants
- FDA label
- Download (121 KB)
- Download (78.8 KB)
- Clinical Trials
Phase Status Purpose Conditions Count 3 Completed Treatment Pain 1 3 Recruiting Treatment Liver Cirrhosis 1 4 Completed Treatment Back Pain Lower Back 1 4 Completed Treatment Rib Fractures / Wounds and Injuries 1
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- Dosage forms
Form Route Strength Kit Oral 500 mg/1 Injection Intramuscular; Intravenous 100 mg/1mL Injection Parenteral 100 mg/1mL Injection, solution Intramuscular; Intravenous 1000 mg/10mL Tablet Oral 500 mg/1 Tablet Oral 750 mg/1 Tablet, coated Oral 500 mg/1 Tablet, coated Oral 750 mg/1 Tablet Oral Injection, solution Intramuscular; Intravenous 100 mg/1mL Tablet Oral Tablet, film coated Oral 500 mg/1 Tablet, film coated Oral 750 mg/1 Liquid Intramuscular; Intravenous
Unit description Cost Unit Robaxin-750 750 mg tablet 2.48USD tablet Robaxin 100 mg/ml vial 2.2USD ml Robaxin-750 tablet 1.99USD tablet Robaxin 500 mg tablet 1.68USD tablet Methocarbamol powder 0.95USD g Methocarbamol 750 mg tablet 0.49USD tablet Methocarbamol 500 mg tablet 0.38USD tabletDrugBank does not sell nor buy drugs. Pricing information is supplied for informational purposes only.
- Not Available
- Experimental Properties
Property Value Source melting point (°C) 92 MSDS water solubility 2.5g/100mL MSDS logP 0.61 CHEM INSPECT TEST INST (1992)
- Predicted Properties
Property Value Source Water Solubility 4.21 mg/mL ALOGPS logP 0.63 ALOGPS logP 0.45 ChemAxon logS -1.8 ALOGPS pKa (Strongest Acidic) 13.6 ChemAxon pKa (Strongest Basic) -3.4 ChemAxon Physiological Charge 0 ChemAxon Hydrogen Acceptor Count 4 ChemAxon Hydrogen Donor Count 2 ChemAxon Polar Surface Area 91.01 Å2 ChemAxon Rotatable Bond Count 7 ChemAxon Refractivity 59.07 m3·mol-1 ChemAxon Polarizability 24.28 Å3 ChemAxon Number of Rings 1 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 + 0.9638 Blood Brain Barrier + 0.5747 Caco-2 permeable - 0.6689 P-glycoprotein substrate Non-substrate 0.6452 P-glycoprotein inhibitor I Non-inhibitor 0.9411 P-glycoprotein inhibitor II Non-inhibitor 0.8887 Renal organic cation transporter Non-inhibitor 0.9105 CYP450 2C9 substrate Non-substrate 0.8431 CYP450 2D6 substrate Non-substrate 0.7658 CYP450 3A4 substrate Non-substrate 0.606 CYP450 1A2 substrate Inhibitor 0.9107 CYP450 2C9 inhibitor Non-inhibitor 0.9302 CYP450 2D6 inhibitor Non-inhibitor 0.9231 CYP450 2C19 inhibitor Non-inhibitor 0.9066 CYP450 3A4 inhibitor Non-inhibitor 0.9338 CYP450 inhibitory promiscuity Low CYP Inhibitory Promiscuity 0.9542 Ames test Non AMES toxic 0.5776 Carcinogenicity Non-carcinogens 0.9406 Biodegradation Not ready biodegradable 0.8358 Rat acute toxicity 2.2930 LD50, mol/kg Not applicable hERG inhibition (predictor I) Weak inhibitor 0.984 hERG inhibition (predictor II) Non-inhibitor 0.9411
- Mass Spec (NIST)
- Not Available
Spectrum Spectrum Type Splash Key Predicted GC-MS Spectrum - GC-MS Predicted GC-MS Not Available Predicted MS/MS Spectrum - 10V, Positive (Annotated) Predicted LC-MS/MS Not Available Predicted MS/MS Spectrum - 20V, Positive (Annotated) Predicted LC-MS/MS Not Available Predicted MS/MS Spectrum - 40V, Positive (Annotated) Predicted LC-MS/MS Not Available Predicted MS/MS Spectrum - 10V, Negative (Annotated) Predicted LC-MS/MS Not Available Predicted MS/MS Spectrum - 20V, Negative (Annotated) Predicted LC-MS/MS Not Available Predicted MS/MS Spectrum - 40V, Negative (Annotated) Predicted LC-MS/MS Not Available LC-MS/MS Spectrum - LC-ESI-qTof , Positive LC-MS/MS Not Available LC-MS/MS Spectrum - LC-ESI-qTof , Positive LC-MS/MS Not Available MS/MS Spectrum - , positive LC-MS/MS splash10-02t9-0900000000-97aeacf66e8410c23139 MS/MS Spectrum - , positive LC-MS/MS splash10-02t9-2900000000-df41a784aa756b8e064d
- This compound belongs to the class of organic compounds known as anisoles. These are organic compounds containing a methoxybenzene or a derivative thereof.
- Organic compounds
- Super Class
- Phenol ethers
- Sub Class
- Direct Parent
- Alternative Parents
- Phenoxy compounds / Methoxybenzenes / Alkyl aryl ethers / Carbamate esters / Secondary alcohols / Organic carbonic acids and derivatives / Organopnictogen compounds / Organonitrogen compounds / Organic oxides / Hydrocarbon derivativesCarbonyl compounds show 1 more
- Phenoxy compound / Anisole / Methoxybenzene / Alkyl aryl ether / Monocyclic benzene moiety / Carbamic acid ester / Carbonic acid derivative / Secondary alcohol / Ether / AlcoholOrganooxygen compound / Organonitrogen compound / Hydrocarbon derivative / Organic oxide / Carbonyl group / Organopnictogen compound / Organic oxygen compound / Organic nitrogen compound / Aromatic homomonocyclic compound show 9 more
- Molecular Framework
- Aromatic homomonocyclic compounds
- External Descriptors
- carbamate ester, aromatic ether, secondary alcohol (CHEBI:77498)
- Pharmacological action
- General Function
- Zinc ion binding
- Specific Function
- Reversible hydration of carbon dioxide. Can hydrates cyanamide to urea.
- Gene Name
- Uniprot ID
- Uniprot Name
- Carbonic anhydrase 1
- Molecular Weight
- 28870.0 Da
- Parr JS, Khalifah RG: Inhibition of carbonic anhydrases I and II by N-unsubstituted carbamate esters. J Biol Chem. 1992 Dec 15;267(35):25044-50. [PubMed:1460006]
Drug created on June 13, 2005 07:24 / Updated on July 03, 2020 22:11