Metaxalone
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Mechanism of action
The mechanism of action of metaxalone in humans has not been established, but may be due to general central nervous system depression.
Metaxalone is a CNS depressant that has sedative and skeletal muscle relaxant effects. The precise mechanism of action of the drug is not known. The skeletal muscle relaxant effects of orally administered metaxalone are minimal and are probably related to its sedative effect. The drug does not directly relax skeletal muscle and, unlike neuromuscular blocking agents, does not depress neuronal conduction, neuromuscular transmission, or muscle excitability.
The mechanism of action of metaxalone in humans has not been established, but may be due to general central nervous system depression. Metaxalone has no direct action on the contractile mechanism of striated muscle, the motor end plate or the nerve fiber.
Pharmacodynamics
Metaxalone is a skeletal muscle relaxant indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions. The mode of action of this drug has not been clearly identified, but may be related to its sedative properties. Metaxalone does not directly relax tense skeletal muscles in man.
Pharmacokinetics
Half-life
9.2 (+/- 4.8) hours
Terminal half-life /is/ 9.0 + or - 4.8 hours
Absorption
The absolute bioavailability of metaxalone from Skelaxin tablets is not known.
Metaxalone is metabolized by the liver and excreted in the urine as unidentified metabolites.
800 L
68 +/- 50 L/h [Subjects received 1×400mg tablet under fasted conditions]
66 +/- 51 L/h [Subjects received 2×400 mg tablets under fasted conditions]
Although plasma protein binding and absolute bioavailability of metaxalone are not known, the apparent volume of distribution (V/F ~ 800 L) and lipophilicity (log P = 2.42) of metaxalone suggest that the drug is extensively distributed in the tissues. Metaxalone is metabolized by the liver and excreted in the urine as unidentified metabolites.
Metabolism
Probably hepatic.
Biotransformations...studied in dogs and in man. 5-(3-methyl-5-carboxyphenoxymethyl)-2-oxazolidinone, major metabolite, is excreted in urine and feces; this also occurs in urine as ester glucuronide. Fission of ether linkage...affords...3,5-xylenol and 5-hydroxymethyloxazolidinone. Oxazolidinone ring is stable in mammals.
Yields 5-(5-carboxy-3-methylphenoxymethyl)-2-oxazolidone in man & in dogs, yields 3,5-dimethylphenol in man and in dogs. /From table/
Metaxalone is metabolized by the liver and excreted in the urine as unidentified metabolites.
External links
Fact-sheets from PsychonautWiki. Harm-reduction reference only — not medical advice.