Metaxalone

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Cat Number

API0231539

CAS Number

1665-48-1

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Product Detail Description Scientific Support Customer Q&A

CAS Number

1665-48-1

EINECS

216-777-6

Storage

Store at room temperature

Synonyms

Skelaxin; Zorane; Methaxalonum; Metaxalon; Methoxolone; AHR-438; 5-[(3,5-Dimethylphenoxy)methyl]-1,3-oxazolidin-2-one; Metassalone

Molecular Formula

C12H15NO3

Molecular Weight

221.25

Smiles

CC1=CC(=CC(=C1)OCC2CNC(=O)O2)C

Appearance

White to off-white powder

Melting Point

121-123℃

Boiling Point

453.6℃

Relative Density

1.138

General Description

Metaxalone is a centrally acting skeletal muscle relaxant indicated for the relief of painful musculoskeletal conditions. It is available in oral tablet form and is characterized by a favorable sedative profile compared to other agents in its class. The drug is chemically unrelated to other muscle relaxants such as cyclobenzaprine or methocarbamol, and its precise mechanism remains incompletely understood.

Mechanism of Action

The exact mechanism of metaxalone has not been fully elucidated, but it is believed to act centrally in the brainstem and spinal cord rather than directly on skeletal muscle or the neuromuscular junction. It may produce its effects through generalized central nervous system depression, with potential contributions from GABAergic modulation. Unlike baclofen or tizanidine, it does not have significant direct agonist activity at GABA receptors.

Application

It is indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions such as strains, sprains, and muscle spasms. The recommended dosing schedule is three to four times daily. Compared to other muscle relaxants, metaxalone is associated with less sedation and drowsiness, though it should still be used with caution when operating machinery or driving.

Twenty gel formulations containing metaxalone and diclofenac potassium were prepared using two gelling agents (hydroxypropyl methylcellulose and Carbopol 934). The gels were characterized for pH, drug content, homogeneity, and drug release. Batch F7 was identified as optimal based on favorable pH, high drug content, uniformity, and release profile. A high‑performance liquid chromatography method was developed and validated, demonstrating robustness and accuracy. The work provides a formulation platform for a synergistic topical combination to manage pain and inflammation.

Fig. 1 In vitro drug permeation study of carbopol gels (F3, F7 and F9), zero order kinetic model. (Tiwari A, et al., 2021)

References

Tiwari A, et al. Formulation, validation and evaluation studies on metaxalone and diclofenac potassium topical gel. Environ Anal Health Toxicol. 2021; 36(1):e2021001.

Does Metaxalone require protection from light during storage?

Yes, it is moderately photosensitive. Extended light exposure can cause photodegradation. Store in light-resistant containers in a cool, dry place.

What is the recommended storage temperature for Metaxalone?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, as it may soften the material and accelerate oxidative degradation.

Is Metaxalone hygroscopic, and how does this affect its physical properties?

It exhibits low hygroscopicity, but under high humidity (>75% RH), it may clump. We recommend storage in tightly sealed containers with desiccant for long-term use.

How is the impurity 3,5-dimethylbenzaldehyde monitored during stability?

This known degradation product is quantified using a validated GC or HPLC method, ensuring it remains below the acceptable threshold throughout shelf life.