Medical cannabis has been a topic of increasing interest in Australia and globally. Several published reviews have highlighted some potential of medical cannabis for the treatment of chronic pain conditions1-3, particularly the review by the National Academics of Science, Engineering, and Medicine2. Specifically, cannabis may be beneficial for the treatment of neuropathic pain2. It is estimated that approximately 1 in 5 Australians suffer from chronic pain4, costing an estimated $139 billion in 2018 due to reduced quality of life and loss of productivity.
What is Chronic Neuropathic Pain?
Chronic neuropathic pain is the result of nerve damage3. It can be mediated by central causes (e.g., stroke, multiple sclerosis) and by peripheral causes (e.g., diabetic neuropathy, surgical procedures)5. Neuropathic pain has a high personal and economic burden6 and current treatments are not entirely effective at managing this type of pain, so there is a need for better or additional treatments to improve how we treat neuropathic pain to improve patient’s quality of life. There is the most amount of scientific evidence for the efficacy of cannabis in treating neuropathic pain related to multiple sclerosis (MS), diabetes and human immunodeficiency virus (HIV)7-11.
Multiple Sclerosis (MS)
It has been reported that 60% of individuals with MS will experience MS-related pain, which includes neuropathic and musculoskeletal pain12.
An analysis of several studies of cannabis-based treatments for neuropathic and MS-related pain included seven articles with a total of 298 patients13. Based on pooled data, pain scores decreased by 1.6 ± 0.4 points (on a 11-point scale) and cannabinoids were significantly superior to placebo by 0.8 ± 0.3 points13. The meta-analysis concluded that cannabinoids are effective in treating neuropathic pain in MS13.
Several other studies have evaluated the effect of neuropathic pain in people diagnosed with MS14. A small clinical trial involving 15 people diagnosed with chronic MS found that cannabis combined with gabapentin (an oral pain medication) was effective and well tolerated for treating neuropathic pain14.
Diabetes
Diabetes affects approximately 422 million people around the world15. About 10% of diabetic patients will be diagnosed with neuropathy16. This type of nerve damage typically leads to diabetic patients complaining of pain and hyperalgesia in their feet17, which causes great distress and disability among those affected and decreases quality of life17. Additional treatments for diabetic neuropathy are needed as less than a third of patients suffering from diabetic neuropathy achieve at least a 30% reduction in pain intensity18. Medical cannabis is a promising therapy for this patient base as there is evidence that cannabinoids can help manage diabetic neuropathy.
Toth et al. examined the effect of a synthetic THC cannabinoid as an adjunct treatment for painful refractory diabetic neuropathy in a placebo controlled, randomized withdrawal study8. The treatment was associated with improvements in pain, anxiety, well-being, and sleep disturbances8.
Wallace et al. studied the efficacy of inhaled cannabis in patients with painful diabetic peripheral neuropathy19. Participants were exposed to placebo or THC (1%, 4%, and 7%), with results showing a dose-dependent reduction in pain intensity in response to inhaled cannabis in patients19.
Human Immunodeficiency Virus (HIV)
One complication of HIV infection is the accompanying pain, which has effects on quality of life20.
Chayama et al. conducted in-depth interviews with 25 people living with HIV21. Of those individuals reporting pain, smoking cannabis was a preferred method of consumption, due to its rapid onset21. Participants also preferred indica or high THC products21. This study found pain levels were decreased after cannabis use, with the majority reporting a reduction of 2-3 points on a pain scale with a range of 0 (no pain) to 10 (most severe pain)21. Cannabis use also led to improved daily functioning, and most participants reported using less prescription or illicit drugs (e.g., benzodiazepines, opioids) to manage pain and related symptoms21.
1. Wang, L.; Hong, P. J.; May, C.; Rehman, Y.; Oparin, Y.; Hong, C. J.; Hong, B. Y.; AminiLari, M.; Gallo, L.; Kaushal, A.; Craigie, S.; Couban, R. J.; Kum, E.; Shanthanna, H.; Price, I.; Upadhye, S.; Ware, M. A.; Campbell, F.; Buchbinder, R.; Agoritsas, T.; Busse, J. W., Medical cannabis or cannabinoids for chronic non-cancer and cancer related pain: a systematic review and meta-analysis of randomised clinical trials. BMJ 2021, 374, n1034.
2. National Academies of Sciences, E.; Medicine, The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research. 2017.
3. Pantoja-Ruiz, C.; Restrepo-Jimenez, P.; Castañeda-Cardona, C.; Ferreirós, A.; Rosselli, D., Cannabis and pain: a scoping review. Brazilian Journal of Anesthesiology 2022, 72, 142-151.
4. Welfare, A. I. o. H. a., Chronic Pain in Australia. Welfare, A. I. o. H. a., Ed. Australian Government: Online, 2020.
5. Treede, R.-D.; Rief, W.; Barke, A.; Aziz, Q.; Bennett, M. I.; Benoliel, R.; Cohen, M.; Evers, S.; Finnerup, N. B.; First, M. B., A classification of chronic pain for ICD-11. Pain 2015, 156 (6), 1003.
6. Berger, A.; Dukes, E. M.; Oster, G., Clinical characteristics and economic costs of patients with painful neuropathic disorders. The Journal of Pain 2004, 5 (3), 143-149.
7. Meng, H.; Hanlon, J. G.; Katznelson, R.; Ghanekar, A.; McGilvray, I.; Clarke, H., The prescription of medical cannabis by a transitional pain service to wean a patient with complex pain from opioid use following liver transplantation: a case report. Canadian Journal of Anesthesia/Journal canadien d’anesthésie 2016, 63 (3), 307-310.
8. Toth, C.; Mawani, S.; Brady, S.; Chan, C.; Liu, C.; Mehina, E.; Garven, A.; Bestard, J.; Korngut, L., An enriched-enrolment, randomized withdrawal, flexible-dose, double-blind, placebo-controlled, parallel assignment efficacy study of nabilone as adjuvant in the treatment of diabetic peripheral neuropathic pain. PAIN® 2012, 153 (10), 2073-2082.
9. Svendsen, K. B.; Jensen, T. S.; Bach, F. W., Does the cannabinoid dronabinol reduce central pain in multiple sclerosis? Randomised double blind placebo controlled crossover trial. Bmj 2004, 329 (7460), 253.
10. Rog, D. J.; Nurmikko, T. J.; Friede, T.; Young, C. A., Randomized, controlled trial of cannabis-based medicine in central pain in multiple sclerosis. Neurology 2005, 65 (6), 812-819.
11. Lynch, M. E.; Ware, M. A., Cannabinoids for the treatment of chronic non-cancer pain: an updated systematic review of randomized controlled trials. Journal of neuroimmune pharmacology 2015, 10 (2), 293-301.
12. Foley, P. L.; Vesterinen, H. M.; Laird, B. J.; Sena, E. S.; Colvin, L. A.; Chandran, S.; MacLeod, M. R.; Fallon, M. T., Prevalence and natural history of pain in adults with multiple sclerosis: systematic review and meta-analysis. Pain® 2013, 154 (5), 632-642.
13. Iskedjian, M.; Bereza, B.; Gordon, A.; Piwko, C.; Einarson, T. R., Meta-analysis of cannabis based treatments for neuropathic and multiple sclerosis-related pain. Current medical research and opinion 2007, 23 (1), 17-24.
14. Turcotte, D.; Doupe, M.; Torabi, M.; Gomori, A.; Ethans, K.; Esfahani, F.; Galloway, K.; Namaka, M., Nabilone as an adjunctive to gabapentin for multiple sclerosis-induced neuropathic pain: a randomized controlled trial. Pain Medicine 2015, 16 (1), 149-159.
15. Organization, W. H. Diabetes. https://www.who.int/news-room/fact-sheets/detail/diabetes (accessed 23/06/2022).
16. Low, P. A.; Dotson, R. M., Symptomatic treatment of painful neuropathy. Jama 1998, 280 (21), 1863-1864.
17. Galer, B. S.; Gianas, A.; Jensen, M. P., Painful diabetic polyneuropathy: epidemiology, pain description, and quality of life. Diabetes research and clinical practice 2000, 47 (2), 123-128.
18. Snedecor, S. J.; Sudharshan, L.; Cappelleri, J. C.; Sadosky, A.; Mehta, S.; Botteman, M., Systematic review and meta‐analysis of pharmacological therapies for painful diabetic peripheral neuropathy. Pain practice 2014, 14 (2), 167-184.
19. Wallace, M. S.; Marcotte, T. D.; Umlauf, A.; Gouaux, B.; Atkinson, J. H., Efficacy of inhaled cannabis on painful diabetic neuropathy. The Journal of Pain 2015, 16 (7), 616-627.
20. Pardo, C. A.; McArthur, J. C.; Griffin, J. W., HIV neuropathy: insights in the pathology of HIV peripheral nerve disease. Journal of the Peripheral Nervous System 2001, 6 (1), 21-27.
21. Chayama, K. L.; Valleriani, J.; Ng, C.; Haines‐Saah, R.; Capler, R.; Milloy, M. J.; Small, W.; McNeil, R., The role of cannabis in pain management among people living with HIV who use drugs: A qualitative study. Drug and Alcohol Review 2021, 40 (7), 1325-1333.