Tools for Practice


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


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

BOTTOM LINE
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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EVIDENCE
>20 systematic reviews (60% in last two years). Results presented are statistically significant, ≥30% pain reduction versus placebo unless indicated.    
  • Any chronic pain: Systematic 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 ~0.5 (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  
Context:   
  • 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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Author(s):

  • 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: https://www.cfpc.ca/uploadedFiles/Resources/_PDFs/Authorizing%20Dried%20Cannabis%20for%20Chronic%20Pain%20or%20Anxiety.pdf. Last Accessed: April 1, 2017.

16. College of Physician and Surgeons of Alberta. Marihuana for Medical Purposes. 2016. Available at: http://www.cpsa.ca/standardspractice/cannabis-for-medical-purposes/. Last Accessed: April 1, 2017.

17. College of Physician and Surgeons of British Columbia. Cannabis for Medical Purposes. 2016. Available at: https://www.cpsbc.ca/files/pdf/PSG-Cannabis-for-Medical-Purposes.pdf. Last Accessed: April 1, 2017.

18. College of Physician and Surgeons of Ontario. Marijuana for Medical Purposes. 2016. Available at: http://www.cpso.on.ca/CPSO/media/documents/Policies/Policy-Items/Marijuana-for-Medical-Purposes.pdf?ext=.pdf. Last Accessed: April 1, 2017.

19. Canadian Medical Protective Agency. Medical marijuana: Considerations for Canadian doctors. 2016. Available at: https://www.cmpa-acpm.ca/-/medical-marijuana-new-regulations-new-college-guidance-for-canadian-doctors. Last Accessed: April 1, 2017.

20. Royal Australian College of General Practitioners. Medicinal use of cannabis products. RACGP Position Statement. October 2016. Available at: http://www.racgp.org.au/download/Documents/Policies/Clinical/RACGP-position-on-medical-cannabis.pdf. Last Accessed: July 8, 2017.

21. Abramovici H. Information for Health Care Professionals: Cannabis (marihuana, marijuana) and the cannabinoids. 2013. Available at: http://www.hc-sc.gc.ca/dhp-mps/alt_formats/pdf/marihuana/med/infoprof-eng.pdf. Last Accessed: April 1, 2017.

22. Health Canada. Consumer Information—Cannabis (Marihuana, marijuana). 2016. Available at: http://www.hc-sc.gc.ca/dhp-mps/alt_formats/pdf/marihuana/info/cons-eng.pdf. 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.