Metaxalone

Metaxalone
Systematic (IUPAC) name
5-[(3,5-dimethylphenoxy)methyl]-1,3-oxazolidin-2-one
Clinical data
Trade names Skelaxin
AHFS/Drugs.com monograph
MedlinePlus a682010
Pregnancy
category
  • US: C (Risk not ruled out)
Routes of
administration		 Oral
Legal status
Legal status
Pharmacokinetic data
Bioavailability Unknown
Metabolism Hepatic
Biological half-life 9.2 (± 4.8) hours
Excretion Renal
Identifiers
CAS Number 1665-48-1 YesY
ATC code none
PubChem CID 15459
IUPHAR/BPS 7609
DrugBank DB00660 YesY
ChemSpider 14709 YesY
UNII 1NMA9J598Y YesY
KEGG D00773 YesY
ChEMBL CHEMBL1079604 YesY
Chemical data
Formula C12H15NO3
Molar mass 221.252 g/mol
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Not to be confused with Metolazone, a diuretic.

Metaxalone (marketed by King Pharmaceuticals under the brand name Skelaxin) is a muscle relaxant used to relax muscles and relieve pain caused by strains, sprains, and other musculoskeletal conditions. Its exact mechanism of action is not known, but it may be due to general central nervous system depression. It is considered to be a moderately strong muscle relaxant, with relatively low incidence of side effects. Skelaxin is available in an 800 mg scored tablet. Possible side effects include nausea, vomiting, drowsiness and CNS side effects, such as dizziness, headache, and irritability.

The metabolism of metaxalone involves the liver cytochrome P450 system. Based on the information in the labeling, patients receiving metaxalone therapy and physicians prescribing metaxalone are directed to take precaution when coadministering it with other medications involving the P450 system.[1][2]

Because of potential for side effects, this drug is considered high risk in the elderly. As of 2015 the cost for a typical month of medication in the United States is 100 to 200 USD.[3]

Pharmacokinetics

Metaxalone exhibits increased bioavailability when taken with food.[4] 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%.[5] Thus, based on the information in the labeling, patients receiving metaxalone therapy are directed to take metaxalone with food, and are informed that taking metaxalone with food results in an increase in the oral bioavailability of metaxalone compared to taking metaxalone without food.[6][7][8]

Assay

A literature survey reveals very few methods are reported for the determination of metaxalone to date. Nirogi et al.[5] 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.[9] Metaxalone has been used as an internal standard for few analytical methods[10][11]

References

  1. ↑ United States Patent No. 7,122,566, by Jie Du, et al
  2. ↑ United States Patent No. 7,378,434, by Jie Du, et al
  3. ↑ Hamilton, Richart (2015). Tarascon Pocket Pharmacopoeia 2015 Deluxe Lab-Coat Edition. Jones & Bartlett Learning. p. 2. ISBN 9781284057560.
  4. ↑ Skelaxin Package Insert
  5. 1 2 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.
  6. ↑ id.
  7. ↑ United States Patent No. 6,407,128
  8. ↑ United States Patent No. 6,683,102
  9. ↑ Prafulla Kumar Sahu, M. Mathrusri Annapurna and Dillip Kumar Sahoo, Development and Validation of Stability Indicating RP-HPLC Method for the Determination of Metaxalone in Bulk and its Pharmaceutical Formulations; E-Journal of Chemistry, 2011, 8(S1), S439-S447.
  10. ↑ Mistri H N, Jangid A G, Pudage A, Gomes N, Sanyal M and Shrivastav P, J Chromatogr B, 2007, 853(1), 320-332.
  11. ↑ Mistri H N, Jangid A G, Pudage A and Shrivastav P, J Chromatogr B, 2008, 864(1-2), 137-148.

External links

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