Overview
DESCRIPTION Methocarbamol tablets, USP, a carbamate derivative of guaifenesin, are a central nervous system (CNS) depressant with sedative and musculoskeletal relaxant properties. The chemical name of methocarbamol is 3-(2-meth-oxyphenoxy)-1,2-propanediol 1-carbamate and has the empirical formula C 11 H 15 NO 5 . Its molecular weight is 241.24. The structural formula is shown below.
Mechanism of Action
CLINICAL PHARMACOLOGY The mechanism of action of methocarbamol in humans has not been established, but may be due to general central nervous system (CNS) depression. It has no direct action on the contractile mechanism of striated muscle, the motor end plate or the nerve fiber.
Indications
- INDICATIONS AND USAGE Methocarbamol tablets, USP are indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions. The mode of action of methocarbamol has not been clearly identified, but may be related to its sedative properties. Methocarbamol does not directly relax tense skeletal muscles in man.
Common Doses
- 500 mg
- 750 mg
Dosage
DOSAGE AND ADMINISTRATION Methocarbamol tablets, USP, 500 mg – Adults: Initial dosage: 3 tablets q.i.d. Maintenance dosage: 2 tablets q.i.d. Methocarbamol tablets, USP: 750 mg – Adults: Initial dosage: 2 tablets q.i.d. Maintenance dosage: 1 tablet q.4h. or 2 tablets t.i.d. Six grams a day are recommended for the first 48 to 72 hours of treatment. (For severe conditions 8 grams a day may be administered). Thereafter, the dosage can usually be reduced to approximately 4 grams a day.
Contraindications
- CONTRAINDICATIONS Methocarbamol tablets, USP are contraindicated in patients hypersensitive to methocarbamol or to any of the tablet components.
Side Effects
- ADVERSE REACTIONS Adverse reactions reported coincident with the administration of methocarbamol include: Body as a whole: Anaphylactic reaction, angioneurotic edema, fever, headache Cardiovascular system: Bradycardia, flushing, hypotension, syncope, thrombophlebitis Digestive system: Dyspepsia, jaundice (including cholestatic jaundice), nausea and vomiting Hemic and lymphatic system: Leukopenia Immune system: Hypersensitivity reactions Nervous system: Amnesia, confusion, diplopia, dizziness or lightheadedness, drowsiness, insomnia, mild muscular incoordination, nystagmus, sedation, seizures...
Interactions
- Drug interactions See Warnings and Precautions for interaction with CNS drugs and alcohol. Methocarbamol may inhibit the effect of pyridostigmine bromide. Therefore, methocarbamol should be used with caution in patients with myasthenia gravis receiving anticholinesterase agents.