A centrally acting muscle relaxant whose mode of action has not been established. It is used as an adjunct in the symptomatic treatment of musculoskeletal conditions associated with painful muscle spasm. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1206)
Indication
For use as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions.
Pharmacology
Methocarbamol is a central muscle relaxant for skeletal muscles, used to treat spasms. It is structurally related to guaifenesin. Methocarbamol's exact mechanism of causing skeletal muscle relaxation is unknown. It is thought to work centrally, perhaps by general depressant effects. It has no direct relaxant effects on striated muscle, nerve fibers, or the motor endplate. It will not directly relax contracted skeletal muscles. The drug has a secondary sedative effect.
Toxicity
Symptoms of overdose include blurred vision, coma, drowsiness, low blood pressure, nausea, and seizures.
Affected Organisms
Humans and other mammals
Biotransformation
Hepatic.
Absorption
Rapid. Onset of action is about 30 minutes after oral administration.
Half Life
1.14-1.24 hours
Elimination
Small amounts of unchanged methocarbamol also are excreted in the urine.
Clearance
* 0.2 – 0.8 L/h/kg [healthy]
References
•
Sica DA, Comstock TJ, Davis J, Manning L, Powell R, Melikian A, Wright G: Pharmacokinetics and protein binding of methocarbamol in renal insufficiency and normals. Eur J Clin Pharmacol. 1990;39(2):193-4.
[Pubmed]
Research Area: Neurological Disease Biological Activity: Methocarbamol(Robaxin) is a central muscle relaxant used to treat skeletal muscle spasms. It is the carbamate of guaifenesin, but does not produce guaifenesin as a metabolite, since the carbamate bond is not hydrolyzed metabolically; metabolism is by Phase I ring hydroxylation and O-demethylation, followed by Phase II conjugation. All of the major metabolites are unhydrolyzed carbamates infarction. [1]
A carbamate ester that is glycerol in which one of the primary alcohol groups has been converted to its 2-methoxyphenyl ether while the other has been converted to the corresponding carbamate ester.
References
PubChem Literature
From Data Sources
• Sica DA, Comstock TJ, Davis J, Manning L, Powell R, Melikian A, Wright G: Pharmacokinetics and protein binding of methocarbamol in renal insufficiency and normals. Eur J Clin Pharmacol. 1990;39(2):193-4. Pubmed
• http://en.wikipedia.org/wiki/Methocarbamol
• Baldi, P., et al.: Bioinformatics, 16, 412 (1979)
• Kouznetsov, V., et al.: J. Arch. Pharm., 337, 127 (1979)
• Walters, W., et al.: Drug Discov. Today., 3, 160 (1979)
• Topliss, J., et al.: J. Med. Chem., 22, 1238 (1979)
Harmful (Xn)