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 systemdepression.[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 high risk in the elderly.[medical citation needed]
Pharmacokinetics
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]
Assay
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]
^ abUS 7378434, Du J, Roberts RH, "Metaxalone products, method of manufacture, and method of use", issued 27 May 2008, assigned to Takeda Pharmaceuticals USA Inc.
^Mistri HN, Jangid AG, Pudage A, Gomes N, Sanyal M, Shrivastav P (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): 320–332. doi:10.1016/j.jchromb.2007.03.047. PMID17481969.
^Mistri HN, Jangid AG, Pudage A, Shrivastav P (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): 137–148. doi:10.1016/j.jchromb.2008.02.004. PMID18313371.
External links
"Metaxalone". Drug Information Portal. U.S. National Library of Medicine.