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#143 Acute Back Pain: Is Cyclobenzaprine a reasonable option?

What is the effectiveness of cyclobenzaprine for acute back pain?

Cyclobenzaprine provides reduced pain and increased global improvement over placebo for one in every 3-9 patients in the first week. Cyclobenzaprine is as good or better than diazepam. Cyclobenzaprine 5 mg TID (half-pill) is as effective as 10 mg TID with less somnolence

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  • Systematic reviews and newer Randomized Controlled Trials (RCTs): 
    • Non-benzodiazepine muscle relaxants versus placebo: Three systematic reviews (9-46 RCTs, 820-5,401 patients), differences statistically significant:1-3 
      • Pain: ~12 points lower on 100 point Visual Analogue Scale at 10 days.1 
      • Pain: Attaining undefined ‘pain reduction Number Needed to Treat (NNT)=4-7 at 2-7 days.2 
      • Global efficacy:2 Attaining undefined ‘target’ NNT=4 at days 2-4.  
    • Cyclobenzaprine versus placebo:  
      • One systematic review (14 RCTs, 3,023 patients):4 
        • Global improvement, NNT=3 at ~10 days. 
      • Two publications with two RCTs each, we pooled and did statistics: 
        • Dosing (1,389 patients):5 
          • Backache relief: 50cyclobenzaprine 5 mg TID versus 38% placebo at seven days, NNT=9 (p<0.001).  
            • No difference: 5 mg versus 10 mg or 2.5 mg versus placebo. 
        • Extended or Immediate Release504 patients.6 
          • No difference: Extended release 30 mg OD versus immediate release  10 mg TID.  
    • Cyclobenzaprine plus ibuprofen, three RCTs:7-9 
      • Largest (867 patients): No benefit to adding ibuprofen.7 
      • Two small studies of back/neck strain, (77 and 61 patients): Too underpowered to find differences.8,9 
  • Concerns: Most trials industry sponsored;4 small samples; short duration, poorly-defined targets; unclear if clinically meaningful cut-offs.   
  • No difference in efficacy between the different muscle relaxants although cyclobenzaprine more consistently evaluated.3 
  • Other medications:  
    • Cyclobenzaprine better or equivalent to diazepam.3 
    • Other direct comparisons are lacking but versus placebo: 
      • Acetaminophen: No effect on back pain.10  
      • NSAIDs: NNT=11 for global improvement.11 
  • Adverse events: Dose related somnolence and dry mouth:5 
    • Any somnolence:5 10placebo, 29% for 5 mg TID, 38% for 10 mg TID. 
      • 10mg TID caused more somnolence than 5mg TID, Number Needed to Harm (NNH)=12. 
    • Discontinuation from somnolence:5 0.8placebo, 2.5for 5 mg TID, 5.2% for  10 mg TID. 
  • Guidelines recommend cyclobenzaprine for the treatment of acute low back pain.12 

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  • Emelie Braschi PhD MD
  • G. Michael Allan MD CCFP

1. Machado LA, Kamper SJ, Herbert RD. Rheumatology (Oxford). 2009; 48:520-7.

2. Van Tulder MW, Touray T, Furlan AD. Cochrane Database System Rev. 2003; 4:CD004252.

3. Chou R, Peterson K, Helfand M. J Pain Symptom Manage. 2004; 28:140-75.

4. Browning R, Jackson JL, O'Malley PG. Arch Intern Med. 2001; 161:1613-20.

5. Borenstein DG, Korn S. Clin Ther. 2003; 25:1056-73.

6. Malanga GA, Ruoff GE, Weil AJ, et al. Curr Med Res Opin. 2009; 25:1179-96.

7. Childers MK, Borenstein D, Brown RL, et al. Curr Med Res Opin. 2005; 21:1485-93.

8. Turturro MA, Frater CR, D'Amico FJ. Ann Emerg Med. 2003; 41:818-26.

9. Khwaja SM, Minnerop M, Singer AJ. CJEM. 2010; 12:39-44.

10. Williams CM, Maher CG, Latimer J, et al. Lancet. 2014; 384:1586-96.

11. Roelofs PD, Deyo RA, Koes BW, et al. Cochrane Database Syst Rev. 2008; 1:CD000396.

12. Toward Optimized Practice guideline: Evidence-Informed Primary Care Management of Low Back Pain. 2011. Available at: (Last accessed April 14, 2015).

Authors do not have any conflicts to disclose.