Methocarbamol

Methocarbamol tablet is 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.

The mechanism of action of methocarbamol is thought to be dependant on its central nervous system depressant activity. This action may be mediated through blocking spinal polysynaptic reflexes, decreasing nerve transmission in spinal and supraspinal polysynaptic pathways, and prolonging the refractory period of muscle cells. Methocarbamol has been found to have no effect on contraction of muscle fibres, motor end plates, or nerve fibres.

Route of Administration: Oral

Methocarbamol 500 mg- Adults:

• Initial dosage: 3 tablets q.i.d.
• Maintenance dosage: 2 tablets q.i.d.

Methocarbamol 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.

Pediatric Use: Safety and effectiveness of Methocarbamol in pediatric patients below the age of 16 have not been established.

Methocarbamol may inhibit the effect of Pyridostigmine Bromide. Therefore, Methocarbamol should be used with caution in patients with myasthenia gravis receiving anticholinesterase agents.

Drug/Laboratory Test Interactions: Methocarbamol may cause a color interference in certain screening tests for 5-hydroxyindoleacetic acid (5-HIAA) using nitrosonaphthol reagent and in screening tests for urinary vanillylmandelic acid (VMA) using the Gitlow method. Carcinogenesis, Mutagenesis, Impairment of Fertility Long-term studies to evaluate the carcinogenic potential of Methocarbamol have not been performed. No studies have been conducted to assess the effect of Methocarbamol on mutagenesis or its potential to impair fertility.

Methocarbamol is contraindicated in patients hypersensitive to Methocarbamol or to any of the tablet components.

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, thrombo- phlebitis
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 (including grand mal), vertigo
Skin and special senses: Blurred vision, conjunctivitis, nasal congestion, metallic taste, pruritus, rash, urticaria.

Pregnancy Category C. Animal reproduction studies have not been conducted with Methocarbamol. It is also not known whether Methocarbamol can cause fetal harm when adminis- tered to a pregnant woman or can affect reproduction capacity. Methocarbamol should be given to a pregnant woman only if clearly needed. Methocarbamol and/or its metabolites are excreted in the milk of dogs; however, it is not known whether Methocarbamol or its metabolites are excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Methocarbamol is administered to a nursing woman.

Patients should be cautioned that Methocarbamol may cause drowsiness or dizziness, which may impair their ability to operate motor vehicles or machinery because Methocarbamol may possess a general CNS-depressants effect. Patients should be cautioned about combined effects with alcohol and other CNS depressants. Safe use of Methocarbamol has not been established with regard to possible adverse effects upon fetal development. There have been reports of fetal and congenital abnormalities following in utero exposure to methocarbamol. Therefore, Methocarbamol should not be used in women who are or may become pregnant and particularly during early pregnancy unless in the judgment of the physician the potential benefits outweigh the possible hazards.

Limited information is available on the acute toxicity of methocarbamol. Overdose of methocarbamol is frequently in conjunction with alcohol or other CNS depressants and includes the following symptoms: nausea, drowsiness, blurred vision, hypotension, seizures, and coma. In post-marketing experience, deaths have been reported with an overdose of methocarbamol alone or in the presence of other CNS depressants, alcohol or psychotropic drugs.

Management of overdose includes symptomatic and supportive treatment. Supportive measures include maintenance of an adequate airway, monitoring urinary output and vital signs, and administration of intravenous fluids if necessary. The usefulness of hemodialysis in managing overdose is unknown.

Centrally acting Skeletal Muscle Relaxants

Protect from light, store below 30°C. Keep the medicine out of the reach of children.