What are the safest muscle relaxant medications for older patients?

From the Guidelines

For older patients, the safest muscle relaxants are typically cyclobenzaprine (Flexeril) at a reduced dose of 5 mg once or twice daily, methocarbamol (Robaxin) at 500-750 mg three to four times daily, and tizanidine (Zanaflex) starting at 2 mg and titrating carefully. These medications are preferred because they have shorter half-lives and fewer anticholinergic effects compared to other options, as noted in the study published in the Annals of Internal Medicine 1. Baclofen (Lioresal) at 5 mg three times daily may also be considered, particularly for spasticity.

Key Considerations

• Treatment duration should be limited to 2-3 weeks when possible to minimize side effects.
• Older patients should start with the lowest possible dose and be monitored closely for adverse effects such as sedation, confusion, dry mouth, and urinary retention.
• These medications work by different mechanisms - cyclobenzaprine acts centrally on the brainstem, methocarbamol depresses the central nervous system, tizanidine is an alpha-2 adrenergic agonist, and baclofen is a GABA-B receptor agonist.
• Carisoprodol (Soma) and chlorzoxazone (Parafon Forte) should be avoided in older adults due to their higher risk profiles and inclusion on the Beers Criteria list of potentially inappropriate medications for older adults.

Additional Guidance

• A more recent study published in the Mayo Clinic Proceedings 1 highlights the importance of cautious use of muscle relaxants like orphenadrine in older patients due to its anticholinergic properties and potential for adverse effects.
• The study from the American Family Physician 1 also emphasizes the need for careful consideration of medication side effects in older adults, supporting the choice of medications with fewer anticholinergic effects.

From the FDA Drug Label

Cyclobenzaprine hydrochloride relieves skeletal muscle spasm of local origin without interfering with muscle function. The plasma concentration of cyclobenzaprine is generally higher in the elderly and in patients with hepatic impairment Tizanidine’s capacity to reduce increased muscle tone associated with spasticity was demonstrated in two adequate and well controlled studies in patients with multiple sclerosis or spinal cord injury. Tizanidine clearance is reduced by more than 50% in elderly patients with renal insufficiency

The safest muscle relaxant medications for older patients are cyclobenzaprine and tizanidine. However, they should be used with caution in the elderly due to potential increased plasma concentrations and reduced clearance.

• Cyclobenzaprine should be started with a low dose (5 mg) and titrated slowly upward.
• Tizanidine should be used with caution in renally impaired patients. 2, 2, 3

From the Research

Safest Muscle Relaxant Medications for Older Patients

• The safest muscle relaxant medications for older patients are still a topic of debate, with various studies providing different insights 4, 5, 6, 7, 8.
• A study published in the Journal of the American Geriatrics Society found that baclofen was associated with a higher risk of fall compared to tizanidine, but the risk of fracture was similar among patients treated with baclofen, tizanidine, and cyclobenzaprine 4.
• Another study published in the Journal of pain and symptom management found that baclofen, tizanidine, and dantrolene were effective in treating spasticity, but the evidence for their use in musculoskeletal conditions was limited 5.
• A retrospective cohort study published in the Journal of the American Geriatrics Society found that older adults newly started on baclofen had a greater risk of injury and delirium compared to those started on tizanidine 6.
• A systematic review published in The Cochrane database of systematic reviews found that muscle relaxants did not have a significant benefit in reducing pain in patients with rheumatoid arthritis, and were associated with adverse events such as dizziness and drowsiness 7.
• A retrospective, pre-post cohort analysis published in The Annals of pharmacotherapy found that the use of skeletal muscle relaxants in elderly patients was associated with a small but statistically significant increase in the risk of injury 8.

Comparison of Muscle Relaxant Medications

• Baclofen:
  • Associated with a higher risk of fall compared to tizanidine 4
  • Associated with a greater risk of injury and delirium compared to tizanidine 6
• Tizanidine:
  • Associated with a lower risk of fall compared to baclofen 4
  • Associated with a lower risk of injury and delirium compared to baclofen 6
• Cyclobenzaprine:
  • Associated with a similar risk of fracture compared to baclofen and tizanidine 4
  • Effective in treating musculoskeletal conditions, but the evidence is limited 5
• Dantrolene:
  • Effective in treating spasticity, but the evidence for its use in musculoskeletal conditions is limited 5
  • Associated with rare serious hepatotoxicity 5