What is chronic pain? Who suffers from it?
The reason for chronic pain is an inflammatory response. Every chronic illness like osteoarthritis, cancer or polyneuropathy induces an inflammatory reaction in affected tissues. In osteoarthritis, for example, these are tissues within the affected joint. Chemical mediators released during inflammation activate nociceptors (receptors responsible for feeling pain). Afterwards, the impulse is carried to the spinal cord through peripheral nerves. The end of pain route is located in brain structures responsible for pain sensation. The pain occurs more often with the progress of the ongoing disease. This phenomenon is caused by changes in the innervation of nociceptors caused by long-lasting inflammatory. The result is reducing the threshold of activating pain sensation [2][3]. So, even mild inflammatory response may induce pain. Many people suffer from chronic pain. It is claimed that about ⅓ of the worldwide population may experience this condition [4].
How do we treat chronic pain?
In the pharmacological treatment of chronic pain, we use mainly two classes of drugs: nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids. Both of them may lead to side effects when being used for a long time. The most common adverse effect of NSAIDs drugs is ulceration, which can lead to bleeding and anaemia . Nause and constipation are the most common side effects of opioids. Beyond that, this group of drugs may lead to more severe effects like respiratory depression and physical dependence [17]. The other important thing in chronic pain treatment are interactions between drugs. We must know that a lot of patients has not only one disease, so they take also other drugs. For example, using NSAIDs with corticosteroids (commonly used drugs in inflammatory diseases) significantly increases the risk of gastrointestinal tract bleeding [16].
Why medical cannabis can be a hope for patients with chronic pain?
The human body has the endocannabinoid system which involves some metabolites and two main kinds of receptors: CB1 and CB2. The first one is located mainly in the spinal cord, central and peripheral nervous system. The second one is located mainly on the immune system cells and in other tissues: cardiovascular system, reproductive system, gastrointestinal tract and adipose tissue [16]. The endocannabinoid system is involved in several processes in our body: inflammatory response, pain sensation, reproductive functions, anxiety, food intake and other. Ingredients of medical cannabis - cannabidiol (CBD) and tetrahydrocannabinol (THC) activate CB1 and CB2 receptors. Activation of these structures induces a cascade of biochemical reactions, which leads to suppression of pain and inflammatory [15]. Why cannabis can be a good alternative for pain treatment? As it is already proofed, in contrast to NSAIDs and opioids, the side effects of cannabis are rare and they are not as severe as in long-term using of NSAIDs and opioids. The number of drugs which can interact with CBD and THC is low. Apart from anti-inflammatory and analgesic effects, medical cannabis presents other important feature. When it is used with opioids, it decreases the dose of opioids needed for effective pain treatment [18]. This property can be important in decreasing the risk of opioid dependence and reduce side effects severity.
The current state of cannabis treatment worldwide
Germany
Medical cannabis can be prescribed for serious-ill patients who experiences strong pain which is impossible to treat with NSAIDs and opioids. Medical cannabis is used in the form of spray or drops. The treatment process must be supervised by a doctor. The number of patients using medical cannabis in pain treatment is 800 000 [8][9][10].
Canada
It is claimed that one of five Canadians suffers from chronic pain[6]. It is estimated that 340000 Canadian uses medical cannabis [12]. The most common form of the drug with cannabinoids is an oral spray.
Isreal
Patients with chronic pain can use medical cannabis if they have a license from IMCA. It is claimed that 10-40% of the population suffers from chronic pain. The medical cannabis is supplied in the form of oil and dried flowers which can be smoked or vaporised.[19].
Summary
As you can see, cannabinoids may be a new therapeutic strategy for patients suffering from chronic pain. We already know that cannabis decreases the number of opioids needed for effective pain treatment. This effect can improve life quality of patients with chronic pain.
References
[1]Yasaei, R. (2019, May 11). Chronic Pain Syndrome. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK470523/
[2]Courtney, C. A., Fernández-de-Las-Peñas, C., & Bond, S. (2017, July). Mechanisms of chronic pain - key considerations for appropriate physical therapy management. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5498792/
[3]Scholz, J. (2014, December 15). Mechanisms of chronic pain. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4304360/
[4]Prevalence of Chronic Pain and High-Impact Chronic Pain Among Adults - United States, 2016. (2019, September 16). Retrieved from https://www.cdc.gov/mmwr/volumes/67/wr/mm6736a2.htm#contribAff
[5]Anekar, A. A. (2020, February 17). WHO Analgesic Ladder. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK554435/
[6]Canada, H. (2019, August 8). Government of Canada. Retrieved from https://www.canada.ca/en/health-canada/corporate/about-health-canada/public-engagement/external-advisory-bodies/canadian-pain-task-force/report-2019.html#a1.2
[7]France-Presse, A. (2016, May 3). Germany to legalise cannabis for medicinal purposes. Retrieved from https://www.telegraph.co.uk/news/2016/05/03/germany-to-legalise-cannabis-for-medicinal-purposes/
[8]Kade, C. (2016, May 4). Gröhe: Cannabis gibt es ab 2017 auf Kassenrezept - WELT. Retrieved from https://www.welt.de/politik/deutschland/article154992002/Ab-2017-gibt-es-Cannabis-auf-Kassenrezept.html
[9]Cannabis als Medizin. (n.d.). Retrieved from https://www.bundesgesundheitsministerium.de/ministerium/meldungen/2016/cannabisarzneimittel-kabinett.html
[10]Tagesschau.de. (2014, November 19). Aktuelle Nachrichten - Inland Ausland Wirtschaft Kultur Sport - ARD Tagesschau. Retrieved from https://www.tagesschau.de/thema/cannabis/index.html
[11]Medical Cannabis. (n.d.). Retrieved from https://arthritis.ca/treatment/medication/medical-cannabis
[12]Canada, H. (2018, October 17). Government of Canada. Retrieved from https://www.canada.ca/en/health-canada/services/drugs-medication/cannabis/medical-use-cannabis.html
[13]Government throws its weight behind medical cannabis sector. (2019, November 13). Retrieved April 5, 2020, from https://www.timesofisrael.com/government-throws-its-weight-behind-medical-cannabis-sector/
[14]White paper: Israel's Medical Cannabis innovation. (n.d.). Retrieved from https://investinisrael.gov.il/Documents/RoundTable/medical-cannabis-doc250919.pdf
[15]Ethan B Russo Cannabinoids in the management of difficult to treat pain
Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2503660/
[16]Wongrakpanich, S., Wongrakpanich, A., Melhado, K., & Rangaswami, J. (2018, February 1). A Comprehensive Review of Non-Steroidal Anti-Inflammatory Drug Use in The Elderly. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5772852/
[17]Wongrakpanich, S., Wongrakpanich, A., Melhado, K., & Rangaswami, J. (2018, February 1). A Comprehensive Review of Non-Steroidal Anti-Inflammatory Drug Use in The Elderly. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5772852/
[18]Capano, A., Weaver, R., & Burkman, E. (2020, January). Evaluation of the effects of CBD hemp extract on opioid use and quality of life indicators in chronic pain patients: a prospective cohort study. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/31711352
[19]Medical use of cannabis and cannabinoids. Questions and answers for policymaking December 2018. (2018, December). Retrieved from http://www.emcdda.europa.eu/system/files/publications/10171/20185584_TD0618186ENN_PDF.pdf