What is the use of Cyclobenzaprine (Flexeril)?

From the Guidelines

Cyclobenzaprine should be used for short-term treatment of acute low back pain, with a maximum recommended duration of 2-3 weeks, due to its moderate superiority to placebo for short-term pain relief, as evidenced by a higher-quality Cochrane review 1.

Key Points

• The typical dosage of cyclobenzaprine is 5-10 mg taken orally three times daily.
• For elderly patients or those with liver impairment, starting at a lower dose of 5 mg is advisable.
• Cyclobenzaprine works by acting on the central nervous system to reduce nerve impulses from certain muscle groups, thereby decreasing muscle tone and relieving pain.
• Common side effects include drowsiness, dry mouth, and dizziness, making it important to avoid activities requiring alertness until you know how the medication affects you.
• Cyclobenzaprine should not be taken with MAO inhibitors, and caution is needed when combining it with other CNS depressants like alcohol or benzodiazepines.

Efficacy and Safety

• A higher-quality Cochrane review found skeletal muscle relaxants, including cyclobenzaprine, to be moderately superior to placebo for short-term pain relief in acute low back pain 1.
• The relative risks for not achieving pain relief were 0.80 (CI, 0.71 to 0.89) at 2 to 4 days and 0.67 (CI, 0.13 to 3.44) at 5 to 7 days.
• Skeletal muscle relaxants were associated with a higher total number of adverse events (RR, 1.50 [CI, 1.14 to 1.98]) and central nervous system adverse events (RR, 2.04 [CI, 1.23 to 3.37]) compared with placebo.

Recommendations

• Cyclobenzaprine should be used for short-term treatment of acute low back pain, with a maximum recommended duration of 2-3 weeks.
• It's not recommended for long-term use due to lack of evidence for extended efficacy and risk of dependence.
• For best results, cyclobenzaprine should be used alongside other treatments such as physical therapy, rest, and appropriate pain management strategies.

From the FDA Drug Label

Cyclobenzaprine hydrochloride tablets are indicated as an adjunct to rest and physical therapy for relief of muscle spasm associated with acute, painful musculoskeletal conditions Improvement is manifested by relief of muscle spasm and its associated signs and symptoms, namely, pain, tenderness, limitation of motion, and restriction in activities of daily living Cyclobenzaprine hydrochloride tablets should be used only for short periods (up to two or three weeks) Cyclobenzaprine hydrochloride tablets have not been found effective in the treatment of spasticity associated with cerebral or spinal cord disease, or in children with cerebral palsy.

Main Use: Cyclobenzaprine is used for relief of muscle spasm associated with acute, painful musculoskeletal conditions.

• It is used as an adjunct to rest and physical therapy.
• Duration of use should be limited to up to two or three weeks.
• It is not effective for treating spasticity associated with cerebral or spinal cord disease, or in children with cerebral palsy 2.

From the Research

Overview of Cyclobenzaprine

• Cyclobenzaprine is a muscle relaxant used to treat muscle spasms and musculoskeletal conditions 3, 4, 5, 6, 7
• It is effective in improving muscle spasm, reducing local pain and tenderness, and increasing range of motion in acute, painful musculoskeletal conditions 3

Efficacy of Cyclobenzaprine

• Studies have shown that cyclobenzaprine 5 or 10 mg TID is effective in treating muscle spasm associated with acute, painful musculoskeletal conditions 3
• Cyclobenzaprine 5 mg TID was as effective as 10 mg TID, and was associated with a lower incidence of sedation 3
• Once-daily cyclobenzaprine extended release (CER) 15- and 30-mg capsules were effective in treating muscle spasm associated with painful musculoskeletal conditions after 4 days of treatment 4

Safety and Tolerability of Cyclobenzaprine

• Cyclobenzaprine was well tolerated, with somnolence and dry mouth being the most common adverse effects 3
• Adverse events were mild and dose-related, with somnolence being the most common reason for discontinuation of treatment 3
• Cyclobenzaprine has been associated with sedative-hypnotic effects, which may be due to its off-target antagonism of central histamine H1 receptors 6

Comparison with Other Muscle Relaxants

• Cyclobenzaprine has been evaluated in the most clinical trials and has consistently been found to be effective in treating musculoskeletal conditions 5
• Carisoprodol and metaxalone also appear to be effective, but carisoprodol's usefulness is mitigated by its potential for abuse 7
• Cyclobenzaprine's efficacy is independent of its sedative effects, which are dose-related 3, 7