Medical Cannabis treatment for Chronic Pain

It is now well established that the endocannabinoid system plays an important role in the modulation of nociceptive and pain states. Key in these roles is the specific positioning of the endocannabinoid signaling machinery at neuronal synapses in pain processing pathways at supraspinal, spinal, and peripheral levels [1].

Acute pain that is poorly managed can lead to chronic pain. In contrast to acute pain, chronic pain is typically considered a far more complex condition which involves physical, psychological, and psychosocial factors, and which contributes to a reduced quality of life [2].

The International Association for the Study of Pain defines pain as chronic if it persists beyond the normal tissue healing time of three to six months. Furthermore, chronic pain is associated with an abnormal state of responsiveness or increased gain of the nociceptive pathways in the central nervous system (referred to as "central sensitization"), as well as with alterations in cognitive functioning [3].

Endocannabinoids, THC, CBD, nabilone and certain synthetic cannabinoids have all been identified as having an anti-nociceptive effect in animal models of chronic pain (inflammatory and neuropathic). A few studies that have used experimental methods having predictive validity for pharmacotherapies used to alleviate chronic pain, have reported an analgesic effect of smoked cannabis. Furthermore, there is more consistent evidence of the efficacy of cannabinoids (smoked/vapourized cannabis, nabiximols, dronabinol) in treating chronic pain of various aetiologies, especially in cases where conventional treatments have been tried and have failed [4].

References

[1] Guindon J, Hohmann AG. The endocannabinoid system and pain. CNS.Neurol.Disord Drug Targets. 2009 12;8(1996-3181; 1871-5273; 6):403-21.

[2] Berlach DM, Shir Y, Ware MA. Experience with the synthetic cannabinoid nabilone in chronic noncancer pain. Pain Med. 2006 01;7(1526-2375; 1526-2375; 1):25-9.

[3] de Vries M, van Rijckevorsel DC, Wilder-Smith OH, van Goor H. Dronabinol and chronic pain: Importance of mechanistic considerations. Expert Opin Pharmacother 2014 Aug;15(11):1525-34.

[4] Whiting PF, Wolff RF, Deshpande S, Di Nisio M, Duffy S, Hernandez AV, Keurentjes JC, Lang S, Misso K, Ryder S, et al. Cannabinoids for medical use: A systematic review and meta-analysis. JAMA 2015 Jun 23-30;313(24):2456-73.