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Action/Kinetics:
Beneficial effect may be related to the sedative properties of the drug. Has no direct effect on the contractile mechanism of striated muscle, the motor endplate, or the nerve fiber and it does not directly relax tense skeletal muscles. Of limited usefulness. May be given IM or IV in polyethylene glycol 300 (50% solution). PO therapy should be initiated as soon as possible.
Onset: 30 min.
Peak plasma levels: 2 hr after 2 g.
t
1/2: 1-2 hr. Inactive metabolites are excreted in the urine.
Uses:
Adjunct for the relief of acute, painful musculoskeletal conditions (e.g., sprains, strains). Adjunct in tetanus.
Contraindications:
Hypersensitivity, when muscle spasticity is required to maintain upright position, seizure disorders, pregnancy, lactation, children under 12 years. Renal disease (parenteral dosage form only since it contains polyethylene glycol 300).
Special Concerns:
Use with caution in epilepsy and during lactation. Use the injectable form with caution in suspected or known epileptics.
Side Effects:
Following PO use. CNS: Dizziness, drowsiness, lightheadedness, vertigo, lassitude, headache.
GI: Nausea.
Miscellaneous: Allergic symptoms including rash, urticaria, pruritus, conjunctivitis, nasal congestion, blurred vision, fever.
Following IV use (in addition to the preceding). CV: Hypotension, bradycardia, syncope.
CNS: Fainting, mild muscle incoordination.
Miscellaneous: Metallic taste, GI upset, flushing, nystagmus, double vision, thrombophlebitis, sloughing or pain at injection site,
anaphylaxis.
Laboratory Test Alterations:
Color interference in 5-HIAA and VMA.
Overdose Management:
Symptoms: CNS depression, including coma, is often seen when methocarbamol is used with alcohol or other CNS depressants.
Treatment: Supportive, depending on the symptoms.
Drug Interactions:
Central nervous system depressants (including alcohol) may
the effect of methocarbamol.
How Supplied:
Injection: 100 mg/mL;
Tablet: 500 mg, 750 mg
Dosage
?Tablets
Skeletal muscle disorders.
Adults, initial: 1.5 g q.i.d. for the first 2-3 days (for severe conditions, 8 g/day may be given);
maintenance: 1 g q.i.d., 0.75 g q 4 hr, or 1.5 g t.i.d.
?IM, IV
Skeletal muscle disorders.
Adults, usual initial: 1 g; in severe cases, up to 2-3 g may be necessary.
IV administration should not exceed 3 days.
Tetanus.
Adults: 1-2 g IV, initially, into tube of previously inserted indwelling needle. An additional 1-2 g may be added to the infusion for a total initial dose of 3 g. May be given q 6 hr (up to 24 g/day may be needed) until
PO administration is feasible.
Pediatric, initial: 15 mg/kg given into tube of previously inserted indwelling needle. Dose may be repeated q 6 hr.
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