Metaxalone is a centrally acting skeletal muscle relaxant used as an adjunct to rest, physical therapy and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions. Current U.S. prescribing information indicates its use in adults and pediatric patients 13 years and older.
Metaxalone is a synthetic small-molecule pharmaceutical compound supplied as an active pharmaceutical ingredient for qualified pharmaceutical formulation and manufacturing applications.
Metaxalone has the molecular formula C12H15NO3 and a molecular weight of 221.25 g/mol. Its chemical name is 5-[(3,5-dimethylphenoxy)methyl]-2-oxazolidinone. It is described as a white to almost white crystalline powder.
Metaxalone is freely soluble in dichloromethane, soluble in methanol, sparingly soluble in ethanol and ethyl acetate, slightly soluble in toluene and isopropanol, and insoluble in water and n-hexane.
The precise mechanism of action of metaxalone has not been fully characterized. Available prescribing information indicates that its muscle-relaxant activity may be related to its sedative properties. Metaxalone does not directly act on the contractile mechanism of striated muscle, the motor end plate or the nerve fiber.
Metaxalone is used as an adjunct to:
The approved indication and patient population can vary by jurisdiction and product.
Metaxalone API can be evaluated using validated procedures for identification, assay, related substances, water content, residue on ignition, residual solvents and elemental impurities, as applicable.
HPLC and spectroscopic methods may be used for identity, assay and impurity profiling. Final acceptance criteria should be based on the manufacturer's validated drug-substance specification and current Certificate of Analysis.
Metaxalone API should be stored in a tightly closed pharmaceutical-grade container under controlled conditions and protected from excessive moisture, heat and direct light.
Specific storage conditions should follow the manufacturer's approved specification.
Metaxalone API may be supplied for qualified pharmaceutical manufacturing, formulation development, analytical testing and research applications, subject to applicable quality and regulatory requirements.
Metaxalone is a pharmaceutical muscle-relaxant API used in oral formulations for approved musculoskeletal applications. Product specifications, Certificate of Analysis, analytical documentation, packaging information and commercial details can be provided according to applicable requirements.
| Parameter | Specification |
|---|---|
| Appearance | White crystalline powder or crystals |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 2.0% |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Water Content | NMT 1.0% |
| Melting Point | 150°C – 154°C |