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Metaxalone: Wikis


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Systematic (IUPAC) name
CAS number 1665-48-1
ATC code none
PubChem 15459
DrugBank APRD00514
Chemical data
Formula C 12H15NO3  
Mol. mass 221.252 g/mol
SMILES eMolecules & PubChem
Pharmacokinetic data
Bioavailability Unknown
Metabolism Hepatic
Half life 9.2 (± 4.8) hours
Excretion Renal
Therapeutic considerations
Pregnancy cat. C(US)
Legal status -only (US)
Routes Oral
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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 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.[1] 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%.[2] 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.[3][4][5]

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,


  1. ^ Skelaxin Package Insert
  2. ^ id.
  3. ^ id.
  4. ^ United States Patent No. 6,407,128
  5. ^ United States Patent No. 6,683,102

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