What are the effects of long-term muscle relaxer use?

Long-Term Muscle Relaxer Use: Effects and Risks

Long-term muscle relaxer use is not recommended due to significant risks including sedation, dependence, and potential for abuse, with limited evidence supporting efficacy beyond short-term use (2-3 weeks). 1, 2

Mechanism and Intended Use

Muscle relaxants represent a diverse group of medications with varying mechanisms of action:

• They are FDA-approved only for short-term relief (2-3 weeks) of acute, painful musculoskeletal conditions 2
• Their effects are primarily non-specific and not directly related to muscle relaxation 3
• They may inhibit polysynaptic myogenic reflexes, but the relationship to pain relief remains unclear 3

Adverse Effects of Long-Term Use

Central Nervous System Effects

• Sedation (primary concern) 3
• Dizziness 3
• Increased risk of falls, particularly in older adults 3, 1

Dependence and Abuse Potential

• Risk for physical and psychological dependence 4, 5
• Potential for misuse, particularly with carisoprodol 4
• Some have been removed from European markets due to abuse concerns (e.g., carisoprodol) 3

Specific Drug Concerns

• Cyclobenzaprine: Anticholinergic effects (dry mouth), structurally similar to tricyclic antidepressants 3, 4
• Carisoprodol: Metabolized to meprobamate (associated with abuse and overdose) 3
• Dantrolene: Black box warning for potentially fatal hepatotoxicity 3
• Tizanidine and chlorzoxazone: Associated with hepatotoxicity (usually reversible) 3

Efficacy for Chronic Pain Conditions

Recent systematic review evidence shows:

• Not beneficial for long-term use in:

  • Low back pain
  • Fibromyalgia
  • Headaches 6

• Potentially beneficial for long-term use in:

  • Painful spasms or cramps
  • Neck pain
  • Trigeminal neuralgia 6

Guidelines for Use

1. Duration: Limited to short periods only (2-3 weeks maximum) 3, 2

   • Adequate evidence for effectiveness in longer periods is not available 2
   • Muscle spasm associated with acute conditions is generally short-duration 2

2. Patient Selection:

   • Avoid in older adults when possible due to increased risk of falls 3, 1
   • Contraindicated in significant liver/kidney disease 1
   • Use with caution in patients with history of substance abuse 5

3. Monitoring:

   • Watch for sedation, dry mouth, and dizziness 1
   • Advise patients to avoid activities requiring mental alertness 1
   • Be vigilant for signs of dependence or misuse 4, 5

Alternative Approaches

For chronic pain conditions requiring longer management:

• Consider baclofen for spasticity from central nervous system injury or demyelinating conditions 3
• For neuropathic pain components, consider anticonvulsants (gabapentin, pregabalin) 1
• For central sensitization, consider tricyclic antidepressants or SNRIs 1
• Physical therapy and non-pharmacological approaches should be prioritized 1

Key Pitfalls to Avoid

1. Prescribing under false assumptions:

   • Muscle relaxants do not directly relax muscles despite their name 3
   • They should not be prescribed in the mistaken belief they relieve muscle spasm 3

2. Dangerous combinations:

   • Avoid co-prescribing with benzodiazepines (increased respiratory depression risk) 1
   • Use caution when combining with other CNS depressants 5

3. Inappropriate continuation:

   • Continuing beyond 2-3 weeks without clear evidence of benefit 2
   • Failing to deprescribe when pain-related goals are not met 6