What is the preferred medication, tizanidine (muscle relaxant) or cyclobenzaprine (muscle relaxant), for treating back pain?

Tizanidine vs Cyclobenzaprine for Back Pain

Direct Recommendation

Tizanidine is the preferred muscle relaxant for back pain over cyclobenzaprine, based on superior evidence quality, demonstrated efficacy in 8 trials for acute low back pain, and specific guideline recommendations from the American College of Physicians. 1, 2

Evidence Supporting Tizanidine

For acute low back pain:

• Tizanidine demonstrated efficacy in 8 clinical trials, while cyclobenzaprine has only 1 lower-quality trial for chronic low back pain that did not even report pain intensity or global efficacy 1
• The American College of Physicians specifically recommends tizanidine as the preferred muscle relaxant option due to its efficacy and safety profile 2, 3
• Tizanidine provides initial pain relief by day 2 and complete relief by day 4, compared to day 3 and day 7 respectively with NSAIDs alone 4
• When combined with acetaminophen or NSAIDs, tizanidine consistently provides greater short-term pain relief than monotherapy in high-quality trials 1, 2

For radicular symptoms (sciatica/leg pain):

• Tizanidine is the preferred muscle relaxant specifically for lumbar radiculopathy 2, 3
• Starting dose: 2-4 mg, titrated as needed 2, 3

Evidence on Cyclobenzaprine

Limited and lower-quality evidence:

• Only 1 lower-quality trial exists for cyclobenzaprine in chronic low back pain available in the United States, and it failed to report pain intensity or global efficacy 1
• A meta-analysis showed cyclobenzaprine is more effective than placebo (odds ratio 4.7), but the effect is modest (effect size 0.38-0.58) and greatest only in the first 4 days 5
• No significant difference was found between cyclobenzaprine and diazepam for global improvement in chronic low back pain 1
• Cyclobenzaprine has limited evidence specifically for radiculopathy 2

Practical Treatment Algorithm

Step 1: Initial therapy

• Start with NSAIDs as first-line treatment 3, 6
• If muscle spasm is prominent or NSAIDs provide inadequate relief, add tizanidine 3

Step 2: Tizanidine dosing

• Begin with 2 mg up to three times daily, particularly in older adults 2
• Titrate dose as needed based on response 2, 3

Step 3: Duration

• Limit treatment to 1-2 weeks (7-14 days) for acute back pain 2, 3
• Reassess after this time-limited course 2, 3

Step 4: For radicular symptoms

• Consider adding gabapentin to tizanidine for patients with radiculopathy 2, 3

Safety Considerations and Monitoring

Common adverse effects (both agents):

• All skeletal muscle relaxants increase CNS adverse events (RR 2.04) compared to placebo 1
• Drowsiness is the most common side effect 1, 2
• Tizanidine: drowsiness occurred in 22% but was generally well-tolerated with adverse effects <6% 4, 7
• Cyclobenzaprine: drowsiness is common and adverse effects occur more frequently than with tizanidine 5

Specific monitoring for tizanidine:

• Monitor for hepatotoxicity (generally reversible) 2, 3
• Monitor for hypotension and sedation 2

Combination therapy benefits:

• Adding tizanidine to NSAIDs increases CNS adverse events (RR 2.44) but may reduce gastrointestinal adverse events (RR 0.54) 1, 2

Critical Pitfalls to Avoid

• Do not use long-term: Evidence supports only short-term use (1-2 weeks maximum) due to limited data on long-term benefits and risks 2, 3
• Do not use cyclobenzaprine for radiculopathy: Tizanidine has specific evidence for this indication while cyclobenzaprine does not 2
• Do not assume all muscle relaxants are equivalent: There is insufficient evidence that any specific muscle relaxant is superior to others in general, but tizanidine has the strongest evidence base for back pain specifically 1
• Assess response early: Evaluate pain relief within 2-4 days; if no improvement, reassess diagnosis and consider alternative therapies 2