Tools for Practice

#199 Missing “High” Quality Evidence: Medical Cannabinoids for Pain?

Are medical cannabinoids (MC) effective for the treatment of pain?

Evidence for inhaled marijuana for pain is too sparse and poor to provide good evidence-based guidance. Synthetic MC-derived products may modestly improve neuropathic pain for one in 11-14 users but perhaps not for other pain types. Additionally, longer and larger studies (better evidence) show no effect. Adverse events are plentiful (see next Tools for Practice). 

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>20 systematic reviews (60% in last two years)Results presented are statistically significant, ≥30% pain reduction versus placebo unless indicated.    
  • Any chronic painSystematic review of systematic reviews.1  
    • Pain reduction (15 Randomized Controlled Trials (RCTs)1,985 patients): 39% versus 30%, Number Needed to Treat (NNT)=11. 
      • Larger (>150 patients) and longer (9-15 weeks) RCTs: No effect.  
    • Mean pain improvement ~0.(0-10 scale, not clinically meaningful).2   
  • Neuropathic pain:  
    • Inhaled MC (five RCTs, 178 patients):3 NNT=6. 
    • Any MC (15 RCTs, 1,619 patients):4 NNT=14. 
  • Cancer pain (six RCTs):5 Pain reduction not statistically significant.  
  • HIV neuropathy, smoked MC (two RCTs, 89 patients):6 NNT=4. 
  • Multiple sclerosis pain (seven RCTs, 298 patients):7 Mean pain improvement over placebo ~0.8 (0-10 scale, borderline clinically insignificant)   
  • Acute pain (seven RCTs)One positive, one negative, and five equivalent to placebo.8    
  • Versus medications: Cannabinoids no better with more adverse events (versus low-dose amitriptyline)9 or inferior with similar adverse events (versus dihydrocodeine).10  
  • No difference in Quality of Life.2,4,5  
  • Very sparse evidence for back pain, fibromyalgia, or osteoarthritis.11-13  
  • Issues:  
    • Cannabinoids generally adjunctive to other pain treatments.1,2   
    • Quality often poor: Of 28 RCTs, two low risk of bias and 16 high risk.2 
    • When assessed, unblinding common, likely exaggerating effectiveness.6,14   
    • For inhaled marijuana, data on pain is very sparse and poor:1  
      • Only five RCTs with 189 patients followed 6 hours to 12 days.   
      • Represents <1% of the total patient-years studied of MC for pain.     
  • Prescribing guidance available through the College of Family Physicians of Canada15 and multiple reliable sources,16-19 including international sites (example20).   
    • Health Canada provides clinician21 and patient information.22   

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  • Caitlin R Finley BHSc MSc
  • G. Michael Allan MD CCFP
  • Nathan P. Beahm BSP PharmD
  • Robert Hauptman MD

1. Allan GM, Finley CR, Ton J, et al. Can Fam Physician. In Press.

2. Whiting PF, Wolff RF, Deshpande S, et al. JAMA. 2015; 313(24):2456-73.

3. Andreae MH, Carter GM, Shaparin N, et al. J Pain. 2015; 16(12):1221-32.

4. Petzke F, Enax-Krumova EK, Häuser W. Schmerz. 2016; 30(1):62-88.

5. Lobos Urbina D, Peña Durán J. Medwave. 2016 Sep 14; 16 Suppl 3:e6539.

6. Phillips TJ, Cherry CL, Cox S, et al. PLoS One. 2010; 5(12):e14433.

7. Iskedjian M, Bereza B, Gordon A, et al. Curr Med Res Opin. 2007; 23(1):17-24.

8. Stevens AJ, Higgins MD. Acta Anaesthesiol Scand. 2017; 61(3):268-80.

9. Ware MA, Fitzcharles MA, Joseph L, et al. Anesth Analg. 2010; 110:604-10.

10. Frank B, Serpell MG, Hughes J, et al. BMJ. 2008; 336(7637):199-201.

11. Fitzcharles MA, Ste-Marie PA, Häuser W, et al. Arthritis Care Res (Hoboken). 2016; 68(5):681-8.

12. Fitzcharles MA, Baerwald C, Ablin J, et al. Schmerz. 2016; 30(1):47-61.

13. Walitt B, Klose P, Fitzcharles MA, et al. Cochrane Database Syst Rev. 2016; 7:CD011694.

14. Wilsey B, Marcotte T, Deutsch R, et al. J Pain. 2013; 14(2):136-48.

15. College of Family Physicians of Canada. Authorizing Dried Cannabis for Chronic Pain or Anxiety: Preliminary Guidance from the College of Family Physicians of Canada. Mississauga, ON: College of Family Physicians of Canada; 2014. Available at: Last Accessed: April 1, 2017.

16. College of Physician and Surgeons of Alberta. Marihuana for Medical Purposes. 2016. Available at: Last Accessed: April 1, 2017.

17. College of Physician and Surgeons of British Columbia. Cannabis for Medical Purposes. 2016. Available at: Last Accessed: April 1, 2017.

18. College of Physician and Surgeons of Ontario. Marijuana for Medical Purposes. 2016. Available at: Last Accessed: April 1, 2017.

19. Canadian Medical Protective Agency. Medical marijuana: Considerations for Canadian doctors. 2016. Available at: Last Accessed: April 1, 2017.

20. Royal Australian College of General Practitioners. Medicinal use of cannabis products. RACGP Position Statement. October 2016. Available at: Last Accessed: July 8, 2017.

21. Abramovici H. Information for Health Care Professionals: Cannabis (marihuana, marijuana) and the cannabinoids. 2013. Available at: Last Accessed: April 1, 2017.

22. Health Canada. Consumer Information—Cannabis (Marihuana, marijuana). 2016. Available at: Last Accessed: April 1, 2017.

Authors Allan, Finley, Beahm do not have any conflicts of interest to declare.

Author Hauptman was a speaker with honoraria (Cannimed) in the past two calendar years.