What are the proper usage and precautions for cyclobenzaprine (muscle relaxant)?

Cyclobenzaprine: Proper Usage and Precautions

Cyclobenzaprine should be prescribed at 5 mg three times daily for most patients, with the option to increase to 10 mg three times daily based on individual response, and should not be used for longer than 2-3 weeks due to risk of dependence and adverse effects. 1

Dosage and Administration

• Standard dosage is 5 mg three times daily, which may be increased to 10 mg three times daily if needed 1
• Lower dosing (5 mg) should be considered for elderly patients and those with hepatic impairment 1
• Extended-release formulation (30 mg once daily) provides comparable systemic exposure to immediate-release (10 mg three times daily) with a more consistent concentration-time profile 2, 3
• Treatment duration should not exceed 2-3 weeks as longer use is not recommended 1
• If discontinuing after long-term use, implement a gradual taper over 2-3 weeks to prevent withdrawal symptoms including malaise, nausea, and headache 4, 5

Mechanism and Clinical Uses

• Cyclobenzaprine is a centrally acting skeletal muscle relaxant structurally related to tricyclic antidepressants 5, 4
• Primarily indicated for relief of muscle spasm associated with acute, painful musculoskeletal conditions 6, 7
• Has shown efficacy in fibromyalgia management, though with only a weak recommendation (75% expert agreement) 5
• 5 mg TID has demonstrated similar efficacy to 10 mg TID with lower incidence of sedation 6

Precautions and Contraindications

• Use with caution in patients with:

  • History of urinary retention due to anticholinergic effects 1
  • Angle-closure glaucoma or increased intraocular pressure 1
  • Hepatic impairment (start with lower dose and titrate slowly) 1
  • Elderly patients (increased risk of adverse effects) 1

• Contraindicated with:

  • MAO inhibitors due to risk of life-threatening interactions 1
  • During acute recovery phase of myocardial infarction 1
  • Patients with heart block, conduction disturbances, or heart failure 1

Adverse Effects

• Most common adverse effects include:

  • Drowsiness/sedation (dose-related) 6, 7
  • Dry mouth (anticholinergic effect) 6, 7
  • Other anticholinergic effects: confusion, hallucinations, constipation, urinary retention 4, 1

• Potential for drug interactions:

  • Enhanced effects with alcohol, barbiturates, and other CNS depressants 1
  • Risk of serotonin syndrome when combined with SSRIs, SNRIs, TCAs, tramadol, bupropion, meperidine, verapamil, or MAO inhibitors 1

Special Considerations

• Hold cyclobenzaprine on the day of surgery due to potential interactions with anesthetics and sedatives 5
• Cyclobenzaprine may impair mental/physical abilities required for operating machinery or driving 1
• The American Geriatrics Society Beers Criteria® identifies muscle relaxants including cyclobenzaprine as potentially inappropriate medications for older adults due to anticholinergic effects and sedation 5
• In patients with fibromyalgia, cyclobenzaprine may be considered but has only moderate evidence quality 5

Patient Education

• Advise patients about sedative effects and to avoid alcohol and other CNS depressants while taking cyclobenzaprine 1
• Inform patients about anticholinergic side effects to monitor for (dry mouth, constipation, urinary retention) 4, 1
• Warn patients about the risk of serotonin syndrome when combined with other serotonergic medications 1
• Instruct patients not to abruptly discontinue medication after prolonged use 4, 5