Clinical data
Trade namesSkelaxin
License data
Routes of
By mouth
ATC code
  • None
Legal status
Legal status
Pharmacokinetic data
Elimination half-life9.2 (± 4.8) hours
  • 5-[(3,5-dimethylphenoxy)methyl]-1,3-oxazolidin-2-one
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.015.253 Edit this at Wikidata
Chemical and physical data
Molar mass221.256 g·mol−1
3D model (JSmol)
  • O=C2OC(COc1cc(cc(c1)C)C)CN2
  • 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) checkY

Metaxalone, sold under the brand name Skelaxin, is a muscle relaxant medication used to relax muscles and relieve pain caused by strains, sprains, and other musculoskeletal conditions.[1] Its exact mechanism of action is not known, but it may be due to general central nervous system depression.[1] It is a moderately strong muscle relaxant, with relatively low incidence of side effects.[citation needed]

Common side effects include nausea, vomiting, drowsiness, and central nervous system (CNS) side effects, such as dizziness, headache, and irritability.[1]

The metabolism of metaxalone involves enzymes CYP1A2 and CYP2C19 in the cytochrome P450 system.[medical citation needed] Because many medications are metabolized by enzymes in this system, precaution must be taken when administering it with other medications involving the P450 system to avoid interactions.[2]

Because of the potential for side effects, this drug is considered a high risk in the elderly.[medical citation needed]


Metaxalone exhibits increased bioavailability when taken with food.[3] Specifically, in one study, compared to fasted conditions, the presence of food at the time of drug administration increased Cmax by 77.5%, AUC0-t by 23.5%, and AUC0-∞ by 15.4%.[4] Metaxalone is a substrate of CYP1A2 and CYP2C19, an inhibitor of CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A, and an inducer of CYP1A2 and CYP3A4.[2]


A literature survey reveals very few methods are reported for the determination of metaxalone to date. Nirogi et al.[4] reported a liquid chromatographic method coupled to tandem mass spectrometry for the quantification of metaxalone in human plasma. A stability-indicating HPLC method was introduced by P.K. Sahu et al.[5] Metaxalone has been used as an internal standard for few analytical methods.[6][7]


  1. ^ a b c d "Skelaxin- metaxalone tablet". DailyMed. 27 April 2018. Retrieved 23 October 2020.
  2. ^ a b United States Patent No. 7,378,434, by Jie Du, et al
  3. ^ Skelaxin Package Insert
  4. ^ a b Nirogi RV, Kandikere VN, Shukla M, Mudigonda K, Shrivastava W, Datla PV (May 2006). "Quantification of Metaxalone in Human Plasma by Liquid Chromatography Coupled to Tandem Mass Spectrometry". J Anal Toxicol. 30 (4): 245–51. doi:10.1093/jat/30.4.245. PMID 16803662.
  5. ^ Sahu, Prafulla Kumar; Annapurna, M. Mathrusri; Kumar, Sahoo Dillip (2011). "Development and Validation of Stability Indicating RP-HPLC Method for the Determination of Metaxalone in Bulk and its Pharmaceutical Formulations". e-Journal of Chemistry. 8 (s1): S439–S447. doi:10.1155/2011/645710.
  6. ^ Mistri, HN; Jangid, AG; Pudage, A; Gomes, N; Sanyal, M; Shrivastav, P (15 June 2007). "High throughput LC-MS/MS method for simultaneous quantification of lamivudine, stavudine and nevirapine in human plasma". Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences. 853 (1–2): 320–32. doi:10.1016/j.jchromb.2007.03.047. PMID 17481969.
  7. ^ Mistri, HN; Jangid, AG; Pudage, A; Shrivastav, P (15 March 2008). "HPLC-ESI-MS/MS validated method for simultaneous quantification of zopiclone and its metabolites, N-desmethyl zopiclone and zopiclone-N-oxide in human plasma". Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences. 864 (1–2): 137–48. doi:10.1016/j.jchromb.2008.02.004. PMID 18313371.