DIsease Description

Chronic Pain is a very broad medical disorder comprised of many different pain syndromes and underlying reasons for the symptoms[1]. Pain is influenced by many different elements other than physical neural inputs including the brain, emotional and social factors. As a result acute pain differs from chronic pain and cancer related pain differs from non-malignant pain, making comparison between these different groups important when determining what treatment to use[2].

The International Association for the Study of Pain defines chronic pain as pain persisting beyond the normal tissue healing time (3 - 6 months) [3]. Chronic pain is associated with an abnormal neuron responsiveness or increased gain of nerve pathways to the brain, as well as with alterations in the brains interpretation of the signals[2].

In this group we are specifically referring to chronic pain that is not a result of cancer.

Disease Prevelance

The prevalence of non-specific chronic pain in the general population is reported to be as high as 55%[4,5].

Current Treatment Options

Chronic pain remains a very task for today's doctors due to a lack of effective treatments. Controversially opioids have been and continue to be regularly prescribed in chronic pain treatment. There are very serious concerns about their long-term effectiveness and the major issue of addiction [6]. Evidence suggests that in some patients long term opioid exposure may actually worsen a patients pain[2].

Evidence for and Proposed Mechanism of Action of Cannabinoid Therapeutics

In a study in Spain, the evidence that pain states alter the endocannabinoid receptor system at key sites involved in pain processing is discussed, and how the changes may inform the development of cannabinoid-based analgesics. According to this study, "cannabinoid ligands produce well documented analgesic effects mediated by the CB1 and CB2 receptors; however, other receptor systems may also contribute, in particular in inflammatory and neuropathic pain states. The emerging evidence that the levels of cannabinoid receptors, their ligands and biologically active metabolites are altered in a tissue-specific manner under pathological conditions, such as chronic pain states, may support a more targeted approach to the development of cannabinoid-based analgesics."[8]

There has been a lot of encouraging research surrounding the issue of cannabinoid treatments for chronic pain. Animal studies using either acute or chronic pain models have demonstrated significant pain relieving effects of Cannabinoids. However, the role of CBs in human analgesia or antihyperalgesia is less well documented [7].

In a systematic review by De Vries et a. it was stated that, "The introduction of CB (cannabinoid) medicines offers an interesting alternative approach in the area of chronic pain management, particularly for cases in which currently available pharmacological treatments are not sufficient. Scientific literature on clinical research regarding medicinal CBs lags far behind the extensive anecdotal experiences of both patients and their physicians. The majority of clinical trials in patients with chronic non-malignant pain summarized in this review reported improvement in pain scores in favor of products containing dronabinol."[2] 1. Beaulieu P, Ware M. Reassessment of the role of cannabinoids in the management of pain. Curr Opin Anaesthesiol 2007;20(5):473-7

2. de Vries et al. Dronabinol and chronic pain: importance of mechanistic considerations. Expert Opin. Pharmacother. (2014) 15(11):1525-1534

3. Merskey H, Bogduk N. Classification of chronic pain: descriptions of chronic pain syndromes and definitions of pain terms. 2013. International Association for the Study of Pain (IASP), Task Force on Taxonomy, Seattle 1994

4. Andersson HI, Ejlertsson G, Leden I, Rosenberg C. Chronic pain in a geographically defined general population: studies of differences in age, gender, social class, and pain localization. Clin J Pain. 1993;9(3):174-82.

5. Elliott AM, Smith BH, Penny KI, Smith WC, Chambers WA. The epidemiology of chronic pain in the community. Lancet. 1999 Oct; 354(9186):1248-52.

6. Noble M, Tregear SJ, Treadwell JR, Schoelles K. Long-term opioid therapy for chronic noncancer pain: a systematic review and meta-analysis of efficacy and safety. J Pain Symptom Manage 2008;35(2):214-28

7. Karst M, Wippermann S, Ahrens J. Role of cannabinoids in the treatment of pain and (painful) spasticity. Drugs 2010;70(18):2409-38

8. Sagar, Devi Rani et al. “Dynamic Regulation of the Endocannabinoid System: Implications for Analgesia.” Molecular Pain 5 (2009): 59. PMC. Web. 20 Nov. 2014.