What is metaxalone (a muscle relaxant)?

From the Guidelines

Metaxalone should be used with caution due to its potential for central nervous system adverse effects, including drowsiness, dizziness, and irritability, and is contraindicated in patients with significant hepatic or renal dysfunction. Metaxalone is an oral centrally acting skeletal muscle relaxant that does not act directly on skeletal muscle 1. The precise mechanism of action is unclear, but it has been associated with multiple central nervous system adverse effects. Key points to consider when prescribing metaxalone include:

• Contraindications: significant hepatic or renal dysfunction
• Potential adverse effects: drowsiness, dizziness, irritability, and drug-induced, hemolytic, or other anemias
• Importance of careful patient selection and monitoring due to potential risks 1. When considering the use of metaxalone, it is essential to weigh the potential benefits against the risks, particularly in patients with pre-existing medical conditions or those taking other medications that may interact with metaxalone 1.

From the FDA Drug Label

The mechanism of action of metaxalone in humans has not been established, but may be due to general central nervous system depression. Metaxalone has no direct action on the contractile mechanism of striated muscle, the motor end plate or the nerve fiber The mode of action of this drug has not been clearly identified, but may be related to its sedative properties. Metaxalone does not directly relax tense skeletal muscles in man.

The primary use of metaxalone is as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions.

• Key points about metaxalone:
  • Mechanism of action not established
  • No direct action on muscle contractile mechanism
  • May be related to sedative properties
  • Does not directly relax tense skeletal muscles
  • Used for relief of discomforts associated with acute, painful musculoskeletal conditions 2, 2

From the Research

Metaxalone Overview

• Metaxalone is a skeletal muscle relaxant used to treat musculoskeletal conditions such as acute low back pain 3, 4, 5, 6
• It is often prescribed in combination with nonsteroidal anti-inflammatory drugs (NSAIDs) to manage pain and improve functional outcomes 5, 6

Efficacy of Metaxalone

• There is limited evidence on the effectiveness of metaxalone compared to placebo in patients with musculoskeletal conditions 3
• A randomized, placebo-controlled trial found that adding metaxalone to ibuprofen did not improve functioning or pain any more than placebo plus ibuprofen by 1 week after an ED visit for acute low back pain 5
• Another study found that metaxalone did not improve outcomes more than placebo in patients with acute low back pain treated with a nonsteroidal anti-inflammatory drug 6

Comparison with Other Skeletal Muscle Relaxants

• Metaxalone has been compared to other skeletal muscle relaxants such as baclofen, tizanidine, and cyclobenzaprine in terms of efficacy and safety 3, 4, 5, 6
• The evidence suggests that these medications have similar efficacy and safety profiles, with some differences in terms of adverse effects 3, 4, 6

Adverse Effects

• Metaxalone can cause adverse effects such as drowsiness, sedation, fatigue, and dizziness 4, 5
• The potential for abuse with metaxalone is not well established, but it is a concern with other skeletal muscle relaxants such as carisoprodol 4