Flexiril (Cyclobenzaprine) Starting Dose
The recommended starting dose of Flexiril (cyclobenzaprine) is 5 mg three times a day. 1
Dosing Guidelines
Initial Dosing
- Start with 5 mg three times daily
- Based on individual response, may increase to 10 mg three times daily 1
Duration of Treatment
- Not recommended for use longer than 2-3 weeks 1
- Clinical trials have shown efficacy within the first week of treatment 2
Special Populations
- Elderly patients: Consider less frequent dosing 1
- Hepatically impaired patients: Consider less frequent dosing 1
Evidence for Dosing Recommendations
The FDA-approved dosing recommendation is based on clinical evidence showing that:
- The 5 mg three times daily regimen is as effective as 10 mg three times daily for most patients 2
- The 5 mg dose is associated with fewer side effects, particularly sedation, compared to the 10 mg dose 2
- Lower doses (2.5 mg three times daily) have not shown significant efficacy compared to placebo 2
Extended-Release Formulation
For the extended-release formulation:
- Starting dose is 15 mg once daily 3
- May be increased to 30 mg once daily if needed 3
- Provides comparable systemic exposure to immediate-release 10 mg three times daily 4
Common Side Effects
The most common adverse effects are dose-related and include:
Clinical Pearls
- Onset of relief is typically apparent within 3-4 doses of the 5 mg regimen 2
- Cyclobenzaprine's efficacy in fibromyalgia has been evaluated, with 85% of patients experiencing side effects and 29% discontinuing treatment 5
- Combination therapy with cyclobenzaprine 5 mg TID plus ibuprofen has not shown superior efficacy compared to cyclobenzaprine 5 mg TID alone for acute neck and back pain with muscle spasm 6
- Serious toxicity is infrequent with doses less than 100 mg in overdose situations 7
Monitoring
- Monitor for sedation, particularly at the beginning of treatment
- Assess efficacy within the first few days of treatment
- Consider discontinuation if no improvement after 2-3 weeks