Methocarbamol

Methocarbamol is presumed to work by depressing the central nervous system, leading to the relaxation of muscles. 

Methocarbamol 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.

Methocarbamol is available under the following different brand names: Robaxin.

Dosages of Methocarbamol

Dosage Forms and Strengths

Tablet

• 500 mg
• 700 mg

Injectable solution

• 100 mg/mL

Dosage Considerations – Should be Given as Follows:

Muscle Spasm

• Adults: 1 g intravenously/intramuscularly (IV/IM); additional doses at every 8 hours until orally; not to exceed 3 g/day
• Total parenteral dose SHOULD NOT EXCEED 3 g/day for more than 3 days unless treating tetanus; if the condition persists, may repeat therapy after a drug-free interval of 48 hours
• 1500 mg orally every 6 hours for 48-72 hours; not to exceed 8 g/day THEN decrease to 4-4.5 g/day divided every 4-8 hours
• Children under 16 years: Safety and efficacy not established
• Children over 16 years: 1500 mg orally every 6 hours for 48-72 hours; not to exceed 8 g/day THEN decrease to 4-4.5 g/day divided every 4-8 hours
• Geriatric: 500 mg orally every 6 hours; may gradually titrate dose to response

Tetanus

Adult

• Adjunct therapy: Initial 1-2 g intravenous (IV) injection (at 300 mg/min), THEN
• Additional 1-2 g IV infusion for a total dose of 3 g initially
• May repeat 1-2 g IV every 6 hours until can give nasogastrically (NG) or orally
• A total of 24 g orally may be needed

Pediatric

• 15 mg/kg/dose IV every 6 hours as needed or 500 mg/m²/dose; not to exceed 1.8 g/m²/day for 3 days only

Dosing Modifications

• Renal failure: Not studied; parenteral dosage form contraindicated due to presence of polyethylene glycol
• Hepatic failure: Not studied
• Geriatric: Considered safe in elderly because of short half-life

Common side effects of methocarbamol include:

• Drowsiness
• Dizziness
• Low white blood cell count (leukopenia) (IV)
• Lightheadedness
• Blurred vision
• Headache
• Fever
• Nausea
• Loss of appetite
• Adynamic ileus
• Changes in taste
• Stomach upset
• Repetitive, uncontrolled eye movements
• Double vision
• Flushing
• Spinning sensation (vertigo)
• Mild muscular incoordination
• Lightheadedness or fainting
• Low blood pressure (hypotension)
• Slow heart rate
• Hives
• Itching
• Rash
• Skin eruptions
• Conjunctivitis with nasal congestion
• Anaphylactic reactions
• Blood clots (IV)
• Sloughing (IV)
• Injection site pain (IV)
• Hemolysis (IV)
• Increased Hgb and RBCs in urine (IV)
• Seizures (IV)

This is not a complete list of side effects and other serious side effects may occur. Call your doctor for information and medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

If your doctor has directed you to use this medication for your condition, your doctor or pharmacist may already be aware of any possible drug interactions or side effects and may be monitoring you for them. Do not start, stop, or change the dosage of this medicine or any medicine before getting further information from your doctor, healthcare provider or pharmacist first.

Severe Interactions of methocarbamol include:

• None

Methocarbamol has moderate interactions with at least 150 different drugs.

Mild Interactions of methocarbamol include:

• eucalyptus
• sage

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

Warnings

This medication contains methocarbamol. Do not take Robaxin if you are allergic to methocarbamol or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.

Contraindications

• Hypersensitivity
• Renal impairment (parenteral)

Effects of Drug Abuse

No information available

Short-Term Effects

• May cause drowsiness/dizziness; patients should not ingest alcohol or other CNS depressants.
• See "What Are Side Effects Associated with Using Methocarbamol?"

Long-Term Effects

• See "What Are Side Effects Associated with Using Methocarbamol?"

Cautions

• May cause drowsiness/dizziness; patients should not ingest alcohol or other CNS depressants.
• May take with food to avoid stomach upset.
• Half-life increases with hepatic impairment.
• Intravenous (IV) formulation not for use in renal impairment (contains polyethylene glycol; injection rate should not exceed 3 mL/min.
• May interfere with screening tests for 5-HIAA and vanillylmandelic acid (VMA).
• Use injection with caution in patients with a history of seizures.
• Sedative effects potentiated when used with other sedatives.
• Medication is poorly tolerated in the elderly.
• Pediatric IV dosing approved only for tetanus.

Pregnancy and Lactation

• Use methocarbamol with caution during pregnancy if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
• It is not known if methocarbamol is excreted in breast milk; use caution if breastfeeding.