Methocarbamol

Indications

Methocarbamol is used for: Muscle Spasm, Tetanus

Adult Dose

Oral Muscle spasm Adult: Initially: 1.5 g q6hr for 48-72 hours; not to exceed 8 g/day THEN decrease to 4-4.5 g/day divided q4-8hr Parenteral 1 g IV/IM; additional doses at q8hr until PO; not to exceed 3 g/day Total parenteral dose should not exceed 3 g/day for >3 days, unless treating tetanus; if condition persists, may repeat therapy after drug-free interval of 48 hr Intravenous Tetanus Adult: Adjunct therapy: Initial 1-2 g IV injection (at 300 mg/min), THEN Additional 1-2 g IV infusion for total dose of 3 g initially May repeat 1-2 g IV q6hr until can give NG or PO Total oral dosage of up to 24 g daily may be needed. Elderly: Dose may need to be reduced by half.

Child Dose

Tetanus 15 mg/kg/dose IV q6hr PRN or 500 mg/m²/dose; not to exceed 1.8 g/m²/day for 3 days only Muscle Spasm <16 years: Safety and efficacy not established >16 years: 1500 mg PO q6hr for 48-72 hours; not to exceed 8 g/day THEN decrease to 4-4.5 g/day divided q4-8hr

Renal Dose

Renal failure: Not studied; parenteral dosage form contraindicated due to presence of polyethylene glycol

Administration

IV Administration Direct IV: Administer undiluted at not to exceed 3 mL (=300 mg undiluted)/min Infusion: Dilute 1 g with up to 250 mL D5W or NS; avoid extravasation, since injection is hypertonic Administer IV while in recumbent position Maintain position 15-30 min following infusion IM Administration Not to exceed 500 mg (5 mL undiluted) should be given into each gluteal region

Contra Indications

Hypersensitivity, Do not admin parenteral solutions in patients with renal impairment, epilepsy or history of epilepsy. Coma or pre-coma states, brain damage, myasthenia gravis

Precautions

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 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 Lactation: Not known if excreted in breast milk; use caution

Pregnancy-Lactation

Pregnancy category: C Lactation: Not known if excreted in breast milk; use caution

Interactions

Action potentiated by alcohol and other CNS depressants. May inhibit effect of pyridostigmine, use with caution with anticholinesterase agents.

Adverse Effects

Side effects of Methocarbamol : Nausea, anorexia, fever, headache, blurred vision, lassitude, drowsiness, dizziness, restlesness, anxiety, confusion, convulsions; hypersensitivity reactions e.g. rashes, pruritus, urticaria, angiodema. Parenteral: Flushing and a metallic taste; incoordination, diplopia, nystagmus, vertigo; sloughing and thrombophloebitis at the site of inj. Potentially Fatal: Parenteral: Syncope, hypotension, bradycardia, anaphylaxis.

Mechanism of Action

Unknown; Methocarbamol is a centrally acting skeletal muscle relaxant whose precise mode of action is not known. It is said to cause general depression of the central nervous system.