|Trade names||Skelaxin, others|
|Drug class||Muscle relaxant|
|Main uses||Musculoskeletal conditions|
|Side effects||Sleepiness, dizziness, headache, nausea, irritability|
|Onset of action||Within 1 hr|
|Duration of action||Up to 6 hrs|
|Elimination half-life||9.2 (± 4.8) hours|
|Chemical and physical data|
|Molar mass||221.256 g·mol−1|
|3D model (JSmol)|
Metaxalone, sold under the brand name Skelaxin among others, is a muscle relaxant used to treat pain due to musculoskeletal conditions. It has not been found to be useful in cerebral palsy. It is taken by mouth. It may be used together with rest and physiotherapy.
Common side effects include sleepiness, dizziness, headache, nausea, and irritability. Other side effects may include anaphylaxis, rash, jaundice, serotonin syndrome, and low blood cells. Safety in pregnancy is not clear. Exactly how it works is not known, but it may be due to general depression of the central nervous system.
It is taken at a dose of 800 mg up to four times per day.
Because of the potential for side effects, this drug is considered a high risk in the elderly.[medical citation needed]
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.
Metaxalone exhibits increased bioavailability when taken with food. 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%. 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.
A literature survey reveals very few methods are reported for the determination of metaxalone to date. Nirogi et al. 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. Metaxalone has been used as an internal standard for few analytical methods.
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- "Skelaxin- metaxalone tablet". DailyMed. 27 April 2018. Archived from the original on 27 October 2020. Retrieved 23 October 2020.
- "Metaxalone Prices, Coupons & Savings Tips - GoodRx". GoodRx. Archived from the original on 25 October 2016. Retrieved 17 November 2021.
- Mitchell, Steve. "Why You Shouldn't Take Soma or Other Muscle Relaxers Every Day". Consumer Reports. Archived from the original on 2020-08-08. Retrieved 2021-11-17.
- "United States Patent No. 7,378,434, by Jie Du, et al". Archived from the original on 2021-10-31. Retrieved 2022-03-14.
- "Skelaxin Package Insert". Archived from the original on 2012-03-11. Retrieved 2021-08-25.
- 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.
- 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.
- 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.
- 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.