Flexeril (Cyclobenzaprine) Dosing and Duration
For acute muscle spasm, start cyclobenzaprine 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 orally three times daily 1, 2
- Alternative dose: May increase to 10 mg three times daily based on individual response, though this offers no additional benefit and increases side effects 1, 2
- Treatment duration: 2-3 weeks maximum 1
The FDA-approved indication is specifically for acute, painful musculoskeletal conditions as an adjunct to rest and physical therapy 1. Evidence does not support use beyond 2-3 weeks because muscle spasm associated with acute conditions is generally short-duration 1.
Efficacy Evidence
- Short-term pain relief: Cyclobenzaprine demonstrates moderate superiority over placebo for pain relief at 2-4 days in acute low back pain 3, 4
- 5 mg vs 10 mg equivalence: The 5 mg three times daily regimen is as effective as 10 mg three times daily, with onset of relief within 3-4 doses 2
- Monotherapy sufficiency: Adding ibuprofen to cyclobenzaprine 5 mg provides no additional benefit over cyclobenzaprine alone 5
Critical Safety Considerations
Central nervous system adverse events occur twice as frequently with muscle relaxants versus placebo (RR 2.04) 3, 4. The most common side effects are:
- Somnolence (dose-dependent, less with 5 mg than 10 mg) 2, 6
- Dry mouth (anticholinergic effect) 3, 7
- Dizziness 2, 6
- Constipation 6
Special Populations and Precautions
Elderly patients: Consider less frequent dosing due to anticholinergic effects and sedation risk 1. The American Geriatrics Society identifies cyclobenzaprine as potentially inappropriate for older adults 4.
Hepatic impairment: Use less frequent dosing 1
Withdrawal management: After prolonged use, taper over 2-3 weeks to prevent withdrawal symptoms (malaise, nausea, headache lasting 2-4 days) 3
Drug interactions: Avoid concurrent use with MAO inhibitors due to serotonin syndrome risk 3
Perioperative Management
Hold cyclobenzaprine on the day of surgery due to potential interactions with sedatives and anesthetic agents 3. The anticholinergic effects (hallucinations, confusion, urinary retention) can complicate perioperative care 3.