Methocarbamol: Difference between revisions

{{Short description|Medication for musculoskeletal pain}}

{{Use dmy dates|date=October 2022}}

{{cs1 config|name-list-style=vanc|display-authors=6}}

{{Infobox drug

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| verifiedrevid = 457287029

| image = Methocarbamol.svg

| width =

| alt =

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<!-- Clinical data -->

| pronounce =

| tradename = Robaxin, Marbaxin, others

| DailyMedID = Methocarbamol

| pregnancy_AUえーゆー = B2

| pregnancy_AUえーゆー_comment =

| pregnancy_category =

| routes_of_administration = [[By mouth]], [[intravenous]]

| class =

| ATCvet =

| ATC_prefix = M03

| ATC_suffix = BA03

| ATC_supplemental = {{ATC|M03|BA53}} {{ATC|M03|BA73}}

<!-- Legal status -->

| legal_AUえーゆー = <!-- S2, S3, S4, S5, S6, S7, S8, S9 or Unscheduled-->

| legal_AUえーゆー_comment =

| legal_BR = <!-- OTC, A1, A2, A3, B1, B2, C1, C2, C3, C4, C5, D1, D2, E, F-->

| legal_BR_comment =

| legal_CA = OTC

| legal_CA_comment =

| legal_DE = <!-- Anlage I, II, III or Unscheduled-->

| legal_DE_comment =

| legal_NZ = <!-- Class A, B, C -->

| legal_NZ_comment =

| legal_UK = POM

| legal_UK_comment = <ref>{{cite web | title=Robaxin-750 - Summary of Product Characteristics (SmPC) | website=(emc) | date=8 August 2017 | url=https://www.medicines.org.uk/emc/medicine/22599/SPC/Robaxin-750 | access-date=19 April 2020}}</ref>

| legal_US_comment =

| legal_UN = <!-- N I, II, III, IV / P I, II, III, IV-->

| legal_UN_comment =

| legal_status = <!-- For countries not listed above -->

<!-- Pharmacokinetic data -->

| bioavailability =

| protein_bound =

| metabolism = Liver

| metabolites =

| onset =

| elimination_half-life = 1.14–1.24 hours<ref name = "halflife">{{cite journal | vauthors = Sica DA, Comstock TJ, Davis J, Manning L, Powell R, Melikian A, Wright G | title = Pharmacokinetics and protein binding of methocarbamol in renal insufficiency and normals | journal = European Journal of Clinical Pharmacology | volume = 39 | issue = 2 | pages = 193–194 | year = 1990 | pmid = 2253675 | doi = 10.1007/BF00280060 | s2cid = 626920 }}</ref>

| duration_of_action =

| excretion =

<!-- Identifiers -->

| CAS_supplemental =

| IUPHAR_ligand = 6829

| KEGG_Ref = {{keggcite|correct|kegg}}

| ChEBI_Ref = {{ebicite|changed|EBI}}

| ChEBI = 6832

| ChEMBL = 1201117

| NIAID_ChemDB =

| PDB_ligand =

| synonyms =

<!-- Chemical and physical data -->

| IUPAC_name = (''RS'')-2-hydroxy-3-(2-methoxyphenoxy)propyl carbamate

| C = 11| H = 15| N = 1| O = 5

| SMILES = O=C(OCC(O)COc1ccccc1OC)N

| Jmol =

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<!-- Definition and medical uses -->

'''Methocarbamol''', sold under the brand name '''Robaxin''' among others, is a medication used for short-term [[musculoskeletal]] pain.<ref name=AHFS2019/><ref name=BNF76>{{cite book|title=British national formulary : BNF 76|date=2018|publisher=Pharmaceutical Press|isbn=9780857113382|page=1093|edition=76}}</ref> It may be used together with rest, physical therapy, and [[pain medication]].<ref name=AHFS2019/><ref name="Robaxin tablet FDA label">{{cite web | title=Robaxin- methocarbamol tablet, film coated | website=DailyMed | date=18 July 2019 | url=https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0db1e8dd-b4fa-491b-a529-0fb939710759 | access-date=19 April 2020}}</ref><ref name="Robaxin injection FDA label">{{cite web | title=Robaxin- methocarbamol injection | website=DailyMed | date=10 December 2018 | url=https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=090a3d3d-92c3-4c30-a648-436461f81702 | access-date=19 April 2020}}</ref> It is less preferred in [[low back pain]].<ref name=AHFS2019/> It has limited use for [[rheumatoid arthritis]] and [[cerebral palsy]].<ref name=AHFS2019/><ref name=Ric2012>{{cite journal | vauthors = Richards BL, Whittle SL, Buchbinder R | title = Muscle relaxants for pain management in rheumatoid arthritis | journal = The Cochrane Database of Systematic Reviews | volume = 1 | pages = CD008922 | date = January 2012 | pmid = 22258993 | doi = 10.1002/14651858.CD008922.pub2 | s2cid = 73769165 }}</ref> Effects generally begin within half an hour.<ref name=AHFS2019/> It is taken by mouth or [[intravenous|injection into a vein]].<ref name=AHFS2019/>

<!-- Side effects and mechanism -->

Common side effect include headaches, sleepiness, and dizziness.<ref name=AHFS2019/><ref name=Liver2017>{{cite book |chapter=Methocarbamol|date=30 January 2017|chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK548286/|title=LiverTox: Clinical and Research Information on Drug-Induced Liver Injury|publisher=National Institute of Diabetes and Digestive and Kidney Diseases|pmid=31643609 }}</ref> Serious side effects may include [[anaphylaxis]], liver problems, confusion, and [[seizure]]s.<ref name=BNF76/> Use is not recommended in [[pregnancy]] and [[breastfeeding]].<ref name=AHFS2019/><ref name=BNF76/> Because of risk of injury, skeletal muscle relaxants should generally be avoided in geriatric patients.<ref name=AHFS2019/> Methocarbamol is a centrally acting [[muscle relaxant]].<ref name=AHFS2019/> How it works is unclear, but it does not appear to affect muscles directly.<ref name=AHFS2019/>

<!-- History and culture -->

Methocarbamol was developed in 1956 in the laboratories of [[Wyeth|A. H. Robins]] (later acquired by [[Pfizer]]). Studies were directed towards the development of [[1,3-Propanediol|propanediol]] derivatives which possessed muscle relaxant properties superior to those of [[mephenesin]], which had low potency and a short duration of action.<ref>''Analytical Profiles of Drug Substances and Excipients, pp. 373''</ref> It was approved for medical use in the United States in 1957.<ref name=AHFS2019>{{cite web |title=Methocarbamol Monograph for Professionals |url=https://www.drugs.com/monograph/methocarbamol.html |website=Drugs.com |publisher=American Society of Health-System Pharmacists }}</ref> It is available as a [[generic medication]].<ref name=AHFS2019/><ref name=BNF76/> It is relatively inexpensive as of 2016.<ref name=Ox2016/> In 2021, it was the 123rd most commonly prescribed medication in the United States, with more than 4{{nbsp}}million prescriptions.<ref>{{cite web | title=The Top 300 of 2021 | url=https://clincalc.com/DrugStats/Top300Drugs.aspx | website=ClinCalc | access-date=14 January 2024 | archive-date=15 January 2024 | archive-url=https://web.archive.org/web/20240115223848/https://clincalc.com/DrugStats/Top300Drugs.aspx | url-status=live }}</ref><ref>{{cite web | title = Methocarbamol - Drug Usage Statistics | website = ClinCalc | url = https://clincalc.com/DrugStats/Drugs/Methocarbamol | access-date = 14 January 2024}}</ref>

== Medical use ==

Methocarbamol is a muscle relaxant used to treat acute, painful musculoskeletal spasms in a variety of musculoskeletal conditions.<ref name=":3">{{cite journal | vauthors = Chou R, Peterson K, Helfand M | title = Comparative efficacy and safety of skeletal muscle relaxants for spasticity and musculoskeletal conditions: a systematic review | journal = Journal of Pain and Symptom Management | volume = 28 | issue = 2 | pages = 140–175 | date = August 2004 | pmid = 15276195 | doi = 10.1016/j.jpainsymman.2004.05.002 | doi-access = free }}</ref> However, there is limited and inconsistent published research on the medication's efficacy and safety in treating musculoskeletal conditions, primarily neck and back pain.<ref name=":3" />

Methocarbamol injection may have a beneficial effect in the control of the neuromuscular spasms of [[tetanus]].<ref name="Robaxin injection FDA label" /> It does not, however, replace the current treatment regimen.<ref name="Robaxin injection FDA label" />

It is not useful in chronic neurological disorders, such as [[cerebral palsy]] or other [[dyskinesia]]s.<ref name="AHFS2019" />

Currently, there is some suggestion that muscle relaxants may improve the symptoms of [[rheumatoid arthritis]]; however, there is insufficient data to prove its effectiveness as well as answer concerns regarding optimal dosing, choice of muscle relaxant, adverse effects, and functional status.<ref name=Ric2012/>

=== Comparison to similar agents ===

The clinical effectiveness of methocarbamol compared to other muscle relaxants is not well-known.<ref name=":3" /> One trial of methocarbamol versus [[cyclobenzaprine]], a well-studied muscle relaxant, in those with localized muscle spasm found there was no significant differences in their effects on improved muscle spasm, limitation of motion, or limitation of daily activities.<ref name=":3" />

== Contraindications ==

Contraindications for methocarbamol include:

* Hypersensitivity to methocarbamol or to any of the injection components.<ref name="Robaxin injection FDA label" />

* For the injectable form, suspected kidney failure or renal pathology, due to large content of [[Polyethylene glycol|polyethylene glycol 300]] that can increase pre-existing [[acidosis]] and [[Uremia|urea retention]].<ref name="Robaxin injection FDA label" />

==Side effects==

Methocarbamol is a centrally acting skeletal muscle relaxant that has significant potential adverse effects, especially on the central nervous system.<ref name="AHFS2019" />

Potential side effects of methocarbamol include:

* Most commonly drowsiness, blurred vision, headache, nausea, and skin rash.<ref name=Liver2017 />

* Possible clumsiness ([[ataxia]]), upset stomach, flushing, mood changes, trouble urinating, itchiness, and fever.<ref name=":9">{{cite web|url=https://medlineplus.gov/druginfo/meds/a682579.html|title=Methocarbamol |website=MedlinePlus |access-date=18 April 2020}}</ref><ref name=":10" />

* Both [[tachycardia]] (fast heart rate) and [[bradycardia]] (slow heart rate) have been reported.<ref name=":10">{{cite web|url=https://www.drugs.com/sfx/methocarbamol-side-effects.html|title=Methocarbamol Side Effects: Common, Severe, Long Term|website=Drugs.com|access-date=18 April 2020}}</ref>

* Hypersensitivity reactions and [[Anaphylaxis|anaphylatic]] reactions are also reported.<ref name="Robaxin tablet FDA label" /><ref name="Robaxin injection FDA label" />

* May cause respiratory depression when combined with [[benzodiazepine]]s, [[barbiturate]]s, [[codeine]], or other muscle relaxants.<ref name=":11">{{cite journal | vauthors = See S, Ginzburg R | title = Choosing a skeletal muscle relaxant | journal = American Family Physician | volume = 78 | issue = 3 | pages = 365–370 | date = August 2008 | pmid = 18711953 }}</ref>

* May cause urine to turn black, blue or green.<ref name=":9" />

While the product label states that methocarbamol can cause [[jaundice]], there is minimal evidence to suggest that methocarbamol causes liver damage.<ref name=Liver2017 /> During clinical trials of methocarbamol, there were no laboratory measurements of liver damage indicators, such as serum [[transaminase]] ([[Aspartate transaminase|AST]]/[[Alanine transaminase|ALT]]) levels, to confirm [[hepatotoxicity]].<ref name=Liver2017 /> Although unlikely, it is impossible to rule out that methocarbamol may cause mild liver injury with use.<ref name=Liver2017 />

=== Elderly ===

Skeletal muscle relaxants are associated with an increased risk of injury among older adults.<ref name=":6">{{cite journal | vauthors = Spence MM, Shin PJ, Lee EA, Gibbs NE | title = Risk of injury associated with skeletal muscle relaxant use in older adults | journal = The Annals of Pharmacotherapy | volume = 47 | issue = 7–8 | pages = 993–998 | date = July 2013 | pmid = 23821610 | doi = 10.1345/aph.1R735 | s2cid = 9037478 }}</ref> Methocarbamol appeared to be less sedating than other muscle relaxants, most notably [[cyclobenzaprine]], but had similar increased risk of injury.<ref name=":11" /><ref name=":6" /> Methocarbamol is cited along with "most muscle relaxants" in the 2012 [[Beers criteria|Beers Criteria]] as being "poorly tolerated by older adults, because of anticholinergic adverse effects, sedation, increased risk of fractures," noting that "effectiveness dosages tolerated by older adults is questionable."<ref>{{cite web|url=https://dcri.org/beers-criteria-medication-list/|title=Beers Criteria Medication List|website=DCRI|access-date=18 October 2020|archive-date=7 November 2020|archive-url=https://web.archive.org/web/20201107180832/https://dcri.org/beers-criteria-medication-list/|url-status=dead}}</ref>

=== Pregnancy ===

Methocarbamol is labeled by the FDA as a [[pregnancy category]] C medication.<ref name="Robaxin injection FDA label" /> The [[Teratology|teratogenic]] effects of the medication are not known and should be given to pregnant women only when clearly indicated.<ref name="Robaxin injection FDA label" />

=== Overdose ===

There is limited information available on the acute toxicity of methocarbamol.<ref name="Robaxin tablet FDA label" /><ref name="Robaxin injection FDA label" /> Overdose is observed frequently in conjunction with CNS depressants such as [[Alcohol (drug)|alcohol]] or [[benzodiazepine]]s and will have symptoms of nausea, drowsiness, blurred vision, [[hypotension]], seizures, and coma.<ref name="Robaxin injection FDA label" /> There are reported deaths with an overdose of methocarbamol alone or in the presence of other CNS depressants.<ref name="Robaxin tablet FDA label" /><ref name="Robaxin injection FDA label" />

===Abuse===

Unlike other carbamates such as [[meprobamate]] and its prodrug [[carisoprodol]], methocarbamol has greatly reduced abuse potential.<ref name="PubMed" /> Studies comparing it to the benzodiazepine [[lorazepam]] and the antihistamine [[diphenhydramine]], along with placebo, find that methocarbamol produces increased "liking" responses and some sedative-like effects; however, at higher doses [[dysphoria]] is reported.<ref name="PubMed" /> It is considered to have an abuse profile similar to, but weaker than, [[lorazepam]].<ref name = "PubMed">{{cite journal | vauthors = Preston KL, Wolf B, Guarino JJ, Griffiths RR | title = Subjective and behavioral effects of diphenhydramine, lorazepam and methocarbamol: evaluation of abuse liability | journal = The Journal of Pharmacology and Experimental Therapeutics | volume = 262 | issue = 2 | pages = 707–720 | date = August 1992 | pmid = 1501118 }}</ref>

== Interactions ==

Methocarbamol may inhibit the effects of [[Pyridostigmine|pyridostigmine bromide]].<ref name="Robaxin tablet FDA label" /><ref name="Robaxin injection FDA label" /> Therefore, methocarbamol should be used with caution in those with [[myasthenia gravis]] taking [[Cholinesterase inhibitor|anticholinesterase]] medications.<ref name="Robaxin injection FDA label" />

Methocarbamol may disrupt certain screening tests as it can cause color interference in laboratory tests for [[5-Hydroxyindoleacetic acid|5-hydroxy-indoleacetic acid (5-HIAA)]] and in urinary testing for [[Vanillylmandelic acid|vanillylmandelic acid (VMA)]] using the Gitlow method.<ref name="Robaxin injection FDA label" />

==Pharmacology==

=== Mechanism of action ===

The mechanism of action of methocarbamol has not currently been established.<ref name="AHFS2019" /> Its effect is thought to be localized to the central nervous system rather than a direct effect on skeletal muscles.<ref name="AHFS2019" /> It has no effect on the motor end plate or the peripheral nerve fiber.<ref name="Robaxin injection FDA label" /> The efficacy of the medication is likely related to its sedative effect.<ref name="AHFS2019" /> Alternatively, methocarbamol may act via inhibition of acetylcholinesterase, similarly to [[carbamate]].<ref>{{cite web| work = PubChem |title= Methocarbamol|url=https://pubchem.ncbi.nlm.nih.gov/compound/4107|access-date=6 July 2020| publisher = U.S. National Library of Medicine }}</ref>

=== Pharmacokinetics ===

In healthy individuals, the plasma clearance of methocarbamol ranges between 0.20 and 0.80 L/h/kg.<ref name="Robaxin injection FDA label" /> The mean plasma elimination half-life ranges between 1 and 2 hours, and the plasma protein binding ranges between 46% and 50%.<ref name="Robaxin injection FDA label" /> The elimination half-life was longer in the elderly, those with [[kidney]] problems, and those with [[liver]] problems.<ref name="Robaxin injection FDA label" />

=== Metabolism ===

Methocarbamol is the [[carbamate]] derivative of [[guaifenesin]], but does not produce guaifenesin as a [[metabolite]], because the carbamate bond is not hydrolyzed metabolically;<ref name="Liver2017" /><ref name="Robaxin injection FDA label" /> its metabolism is by Phase I ring hydroxylation and ''O''-demethylation, followed by Phase II conjugation.<ref name="Robaxin injection FDA label" /> All the major metabolites are unhydrolyzed carbamates.<ref>Methocarbamol. In: ''DRUGDEX System'' [intranet database]. Greenwood Village, Colorado: Thomson Healthcare; c1974–2009 [cited 2009 Feb 10].</ref><ref name="metabolismBruce1971">{{cite journal | vauthors = Bruce RB, Turnbull LB, Newman JH | title = Metabolism of methocarbamol in the rat, dog, and human | journal = Journal of Pharmaceutical Sciences | volume = 60 | issue = 1 | pages = 104–106 | date = January 1971 | pmid = 5548215 | doi = 10.1002/jps.2600600120 }}</ref> Small amounts of unchanged methocarbamol are also excreted in the urine.<ref name="Robaxin tablet FDA label" /><ref name="Robaxin injection FDA label" />

==Society and culture==

Methocarbamol was approved as a muscle relaxant for acute, painful musculoskeletal conditions in the United States in 1957.<ref name=Liver2017 /> Muscle relaxants are widely used to treat low back pain, one of the most frequent health problems in industrialized countries. Currently, there are more than 3 million prescriptions filled yearly.<ref name=Liver2017 /> Methocarbamol and [[orphenadrine]] are each used in more than 250,000 U.S. emergency department visits for lower back pain each year.<ref>{{cite journal | vauthors = Friedman BW, Cisewski D, Irizarry E, Davitt M, Solorzano C, Nassery A, Pearlman S, White D, Gallagher EJ | title = A Randomized, Double-Blind, Placebo-Controlled Trial of Naproxen With or Without Orphenadrine or Methocarbamol for Acute Low Back Pain | journal = Annals of Emergency Medicine | volume = 71 | issue = 3 | pages = 348–356.e5 | date = March 2018 | pmid = 29089169 | pmc = 5820149 | doi = 10.1016/j.annemergmed.2017.09.031 }}</ref> In the United States, low back pain is the fifth most common reason for all physician visits and the second most common symptomatic reason.<ref>{{cite journal | vauthors = Chou R, Huffman LH | title = Medications for acute and chronic low back pain: a review of the evidence for an American Pain Society/American College of Physicians clinical practice guideline | journal = Annals of Internal Medicine | volume = 147 | issue = 7 | pages = 505–514 | date = October 2007 | pmid = 17909211 | doi = 10.7326/0003-4819-147-7-200710020-00008 | s2cid = 32719708 }}</ref> In 80% of primary care visits for low back pain, at least one medication was prescribed at the initial office visit and more than one third were prescribed two or more medications.<ref>{{cite journal | vauthors = Cherkin DC, Wheeler KJ, Barlow W, Deyo RA | title = Medication use for low back pain in primary care | journal = Spine | volume = 23 | issue = 5 | pages = 607–614 | date = March 1998 | pmid = 9530793 | doi = 10.1097/00007632-199803010-00015 | s2cid = 23664539 }}</ref> The most commonly prescribed drugs for low back pain included skeletal muscle relaxants.<ref>{{cite journal | vauthors = Luo X, Pietrobon R, Curtis LH, Hey LA | title = Prescription of nonsteroidal anti-inflammatory drugs and muscle relaxants for back pain in the United States | journal = Spine | volume = 29 | issue = 23 | pages = E531–E537 | date = December 2004 | pmid = 15564901 | doi = 10.1097/01.brs.0000146453.76528.7c | s2cid = 72742439 }}</ref> [[Cyclobenzaprine]] and methocarbamol are on the U.S. [[Medicare (United States)|Medicare]] formulary, which may account for the higher use of these products.<ref name=":6" />

===Economics===

The generic formulation of the medication is relatively inexpensive, costing less than the alternative [[metaxalone]] in 2016.<ref name=Rob2013>{{cite book | vauthors = Robbins LD |title=Management of Headache and Headache Medications |date=2013 |publisher=Springer Science & Business Media |isbn=978-1-4612-2124-1 |page=PT147 |url=https://books.google.com/books?id=Bmh3BQAAQBAJ&dq=Methocarbamol+inexpensive&pg=PT147 }}</ref><ref name=Ox2016>{{cite book | vauthors = Fine PG |title=The Hospice Companion: Best Practices for Interdisciplinary Care of Advanced Illness |date=2016 |publisher=Oxford University Press |isbn=978-0-19-045692-4 |page=PT146 |url=https://books.google.com/books?id=I7NjDQAAQBAJ&dq=Methocarbamol+cost&pg=PT146 }}</ref>

===Marketing===

[[File:Methocarbamol 750 MG Oral Tablet.jpg|thumb|Generic methocarbamol 750mg tablet.]]

Methocarbamol without other ingredients is sold under the brand name Robaxin in the U.K., U.S., Canada<ref>{{cite web|title=ROBAXIN product appearance in Canada|url=https://ctchealth.ca/product/robaxin-500mg/|access-date=13 December 2021|website=ctchealth.ca|date=13 July 2021 }}</ref> and South Africa; it is marketed as Lumirelax in France, Ortoton in Germany and many other names worldwide.<ref>{{cite web|title=Methocarbamol|url=https://www.drugs.com/international/methocarbamol.html|website=Drugs.com|access-date=12 May 2018}}</ref> In combination with other active ingredients it is sold under other names: with [[acetaminophen]] (paracetamol), under trade names Robaxacet and Tylenol Body Pain Night; with [[ibuprofen]] as Robax Platinum; with [[acetylsalicylic acid]] as Robaxisal in the U.S. and Canada.<ref name="ESI">{{cite web | title = New Drugs and Indications Reviewed at the May 2003 DEC Meeting | publisher = [[Express Scripts Incorporated|ESI Canada]] | url = http://www.esi-canada.com/aboutus/news/health_newsflashes/volume5_issue9_newdrugsmay2003.pdf | access-date = 14 November 2008 | url-status = dead | archive-url = https://web.archive.org/web/20110710201457/http://www.esi-canada.com/aboutus/news/health_newsflashes/volume5_issue9_newdrugsmay2003.pdf | archive-date = 10 July 2011 }}</ref><ref name="Tylenol">{{cite web | title = Tylenol Body Pain Night Overview and Dosage | publisher = [[Johnson & Johnson|Tylenol Canada]] | url = http://www.tylenol.ca/adult-pain-relief/tylenol-body-pain-night | format = website | access-date = 23 April 2012 | url-status = dead | archive-url = https://web.archive.org/web/20120331074351/http://www.tylenol.ca/adult-pain-relief/tylenol-body-pain-night | archive-date = 31 March 2012 }}</ref> However, in Spain the tradename Robaxisal is used for the paracetamol combination instead of Robaxacet.{{citation needed|date=April 2020}} These combinations are also available from independent manufacturers under generic names.{{citation needed|date=April 2020}}

== Research ==

Although [[opioid]]s are typically first line treatments in severe pain, several trials suggest that methocarbamol may improve recovery and decrease hospital length of stay in those with muscles spasms associated with [[rib fracture]]s.<ref>{{cite journal | vauthors = Patanwala AE, Aljuhani O, Kopp BJ, Erstad BL | title = Methocarbamol use is associated with decreased hospital length of stay in trauma patients with closed rib fractures | journal = American Journal of Surgery | volume = 214 | issue = 4 | pages = 738–742 | date = October 2017 | pmid = 28088301 | doi = 10.1016/j.amjsurg.2017.01.003 }}</ref><ref>{{cite journal| vauthors = Deloney L, Smith M, Carter C, Privette A, Leon S, Eriksson E |date=January 2020 |title= 946: Methocarbamol reduces opioid use and length of stay in young adults with traumatic rib fractures |journal=Critical Care Medicine |volume=48 |issue=1 |page=452 |doi=10.1097/01.ccm.0000633320.62811.06 |issn=0090-3493|doi-access=free }}</ref><ref>{{cite journal| vauthors = Smith M, Deloney L, Carter C, Leon S, Privette A, Eriksson E |date=January 2020|title=1759: Use of methocarbamol in geriatric patients with rib fractures is associated with improved outcomes |journal=Critical Care Medicine |volume=48 |issue=1 |page=854 |doi=10.1097/01.ccm.0000649332.10326.98 |issn=0090-3493|doi-access=free }}</ref> However, methocarbamol was less useful in the treatment of acute traumatic pain in general.<ref name=":7">{{cite journal | vauthors = Aljuhani O, Kopp BJ, Patanwala AE | title = Effect of Methocarbamol on Acute Pain After Traumatic Injury | journal = American Journal of Therapeutics | volume = 24 | issue = 2 | pages = e202–e206 | date = 2017 | pmid = 26469684 | doi = 10.1097/mjt.0000000000000364 | s2cid = 24284482 }}</ref>

Long-term studies evaluating the risk of development of cancer in using methocarbamol have not been performed.<ref name="Robaxin tablet FDA label" /><ref name="Robaxin injection FDA label" /> There are currently no studies evaluating the effect of methocarbamol on mutagenesis or fertility.<ref name="Robaxin tablet FDA label" /><ref name="Robaxin injection FDA label" />

The safety and efficacy of methocarbamol has not been established in pediatric individuals below the age of 16 except in [[tetanus]].<ref name="Robaxin tablet FDA label" /><ref name="Robaxin injection FDA label" />

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