Cyclobenzaprine for Muscle Spasm: Dosing and Duration
For acute muscle spasm, start cyclobenzaprine at 5 mg three times daily for 2-3 weeks maximum, as this dose provides equivalent efficacy to 10 mg with significantly less sedation. 1, 2
Standard Dosing Regimen
Initial dose: 5 mg three times daily is the optimal starting point for most patients, providing comparable efficacy to 10 mg TID with lower rates of somnolence and better tolerability 2, 3
Alternative dosing: 10 mg three times daily may be considered if 5 mg is insufficient, though this increases sedation risk without clear additional benefit 1, 2
Duration: Limit treatment to 2-3 weeks maximum, as this is an adjunct to rest and physical therapy for acute painful musculoskeletal conditions, and evidence for longer use is lacking 1
Key Evidence Supporting Lower Dose
The 5 mg TID regimen demonstrates:
- Statistically significant improvement in pain relief, medication helpfulness, and global impression of change compared to placebo by day 3-4 2
- Equivalent efficacy to 10 mg TID on all primary measures 2
- Lower incidence of somnolence (reported as adverse event in 0.8% vs 7.3% with immediate-release 10 mg TID) 4
- Efficacy independent of sedation, as demonstrated in subgroup analysis of patients without somnolence 2
Clinical Context and Limitations
Skeletal muscle relaxants show only modest benefit: A Cochrane review found muscle relaxants moderately superior to placebo for short-term (2-4 days) pain relief in acute low back pain, with relative risk of 0.80 for not achieving pain relief 5
Evidence is strongest for acute conditions: Only sparse, lower-quality evidence exists for cyclobenzaprine in chronic muscle spasm, with mixed results 5
Combination therapy offers no advantage: Adding ibuprofen 400-800 mg TID to cyclobenzaprine 5 mg TID provides no superior benefit compared to cyclobenzaprine monotherapy 3
Important Safety Considerations
Central nervous system adverse events occur frequently: Relative risk of 2.04 compared to placebo, including drowsiness, dizziness, confusion, and anticholinergic effects (dry mouth, constipation, urinary retention) 5
Avoid in elderly patients: Due to significant anticholinergic effects and sedation risk; consider less frequent dosing if use is necessary 1, 5
Taper if used long-term: Gradual taper over 2-3 weeks prevents withdrawal symptoms (malaise, nausea, headache lasting 2-4 days), though these are not life-threatening 5, 6
Hold on day of surgery: Due to potential interactions with sedatives and anesthetic agents 5, 6
Contraindicated with MAO inhibitors: Risk of serotonin syndrome due to cyclobenzaprine's structural similarity to tricyclic antidepressants 5