Methocarbamol

• Acute muscle spasms
• Back pain with muscle spasm
• Neck pain and stiffness
• Musculoskeletal injuries
• Adjunct to physical therapy
• Postoperative muscle spasm relief

Methocarbamol is a centrally acting muscle relaxant used to relieve muscle spasms and associated pain. It is commonly prescribed as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions.

How Methocarbamol Works

The exact mechanism of methocarbamol is not fully understood, but it is believed to work primarily through central nervous system depression rather than direct action on skeletal muscle. It may inhibit polysynaptic reflexes in the spinal cord and brain, reducing muscle spasm without affecting muscle function at therapeutic doses.

Available Forms

• Oral tablets: 500 mg and 750 mg (brand name Robaxin)
• Injectable solution: 100 mg/mL for IV or IM administration

The injectable form is typically reserved for severe cases or when oral administration is not feasible. Combination products with NSAIDs or acetaminophen are also available in some countries.

Dosing Information

For adults, the typical oral starting dose is 1500 mg four times daily for the first 48-72 hours, then reduced to 4000-4500 mg daily in divided doses for maintenance. For injectable use, up to 3000 mg daily can be given. Treatment duration is usually limited to 2-3 weeks.

Clinical Effectiveness

Methocarbamol is FDA-approved for relief of discomfort associated with acute, painful musculoskeletal conditions. While it provides symptomatic relief, evidence for long-term efficacy is limited. Best results are achieved when combined with rest, physical therapy, and other appropriate measures.

Important Safety Information

Common side effects include drowsiness, dizziness, lightheadedness, and nausea. The medication can cause CNS depression, impairing ability to drive or operate machinery. Methocarbamol may cause urine to turn brown, black, or green, which is harmless.

Drug Interactions

Methocarbamol may enhance the effects of other CNS depressants including alcohol, benzodiazepines, opioids, and sleep medications. This combination increases risk of excessive sedation and respiratory depression. The medication may interfere with certain laboratory tests for 5-HIAA and VMA.

Special Populations

Elderly patients may be more sensitive to side effects and should use lower doses. The medication should be used cautiously in patients with hepatic or renal impairment. Safety during pregnancy has not been established; use only if clearly needed. It is unknown whether methocarbamol passes into breast milk.

Abuse and Dependence

While methocarbamol has lower abuse potential than many other muscle relaxants, it can still be misused. Physical dependence is uncommon with short-term use at recommended doses. The medication should not be used long-term without medical supervision.

Learn more at MedlinePlus