Professional Information — Methocarbamol

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.

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

Methocarbamol tablets, USP are contraindicated in patients hypersensitive to methocarbamol or to any of the tablet components.

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 (including grand mal), vertigo

Skin and special senses:

Blurred vision, conjunctivitis, nasal congestion, metallic taste, pruritus, rash, urticaria

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.

Overdosage

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.

Treatment

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.

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 C₁₁H₁₅NO₅. Its molecular weight is 241.24. The structural formula is shown below.

Methocarbamol is a white powder, sparingly soluble in water and chloroform, soluble in alcohol (only with heating) and propylene glycol, and insoluble in benzene and n-hexane.

Methocarbamol tablets, USP are available as 500 mg and 750 mg tablets for oral administration. Methocarbamol tablets, USP 500 mg and 750 mg contain the following inactive ingredients: povidone, sodium starch glycolate and magnesium stearate.

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.

How Supplied / Storage and Handling

Methocarbamol tablets, USP

750 mg tablets are modified capsule shape, white to off-white tablet, debossed S 226 on one side and plain on the reverse side.

They are supplied as follows:

Bottles of 30 NDC 63187-130-30

Bottles of 40 NDC 63187-130-40

Bottles of 45 NDC 63187-130-45
Bottles of 60 NDC 63187-130-60
Bottles of 90 NDC 63187-130-90

Store at controlled room temperature, between 20°C and 25°C (68°F and 77°F).
[see USP Controlled Room Temperature].
Dispense in tight container.

Patient Counseling Information

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-depressant effect, patients should be cautioned about combined effects with alcohol and other CNS depressants.