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 cat. C(US) Legal status ℞-only (US) Routes Oral Pharmacokinetic data Bioavailability Unknown Metabolism Hepatic Half-life 9.2 (± 4.8) hours Excretion Renal Identifiers CAS number 1665-48-1 ATC code None PubChem CID 15459 DrugBank APRD00514 ChemSpider 14709 UNII 1NMA9J598Y KEGG D00773 ChEMBL CHEMBL1079604 Chemical data Formula C12H15NO3 Mol. mass 221.252 g/mol SMILES eMolecules & PubChem (what is this?) (verify)
- 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 comes in an 800 mg scored tablet. It previously came in both 400 mg and 800 mg tablets. The 400 mg tablet has been discontinued. Possible side effects include nausea, vomiting, drowsiness and CNS side effects such as dizziness, headache, and irritability.
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 C(max) by 177.5% and increased AUC(last) by 123.5% and AUC(inf) by 115.4%. 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.
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 co-administering with other medications involving the P450 system.
Because of potential for side effects, this drug is on the list for High Risk Medications in the elderly. (See NCQA’s HEDIS Measure: Use of High Risk Medications in the Elderly, http://www.ncqa.org/Portals/0/Newsroom/SOHC/Drugs_Avoided_Elderly.pdf).
- ^ Skelaxin Package Insert
- ^ id.
- ^ id.
- ^ United States Patent No. 6,407,128
- ^ United States Patent No. 6,683,102
- ^ United States Patent No. 7,122,566, by Jie Du, et al
- ^ United States Patent No. 7,378,434, by Jie Du, et al
- Skelaxin (manufacturer's website)
Skeletal muscle relaxants (M03) Peripherally acting
NMJ block)Curare alkaloids
ultra-short duration: Gantacurium
short duration: Mivacurium • Chandonium
intermediate duration: Atracurium • Cisatracurium • Fazadinium • Rocuronium • Vecuronium
long duration: Doxacurium • Dimethyltubocurarine • Pancuronium • Pipecuronium • Laudexium • Gallamineunsorted: Hexafluronium (Hexafluorenium)
Choline derivatives: Suxamethonium (Succinylcholine)Polyalkylene derivatives: Hexamethonium
Centrally actingCarbamic acid estersBenzodiazepinesBentazepam • Diazepam • Lorazepam • Nitrazepam • TetrazepamAnticholinergics (Antimuscarinics)OtherBaclofen • Chlormezanone • Chlorphenesin • Chlorzoxazone • Donepezil • Eperisone • Flopropione • Mephenesin • Mephenoxalone • Metaxalone • Phenyramidol • Pridinol • Promoxolane • Quinine • Thiocolchicoside • Tizanidine • Tolperisone • Trazodone Directly actingCategories:
- Muscle relaxants
- Phenol ethers
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