2 minute read
Medicinal cannabis in managing MSK pain
By C/Prof Alistair Vickery, GP, West Leederville
The most common conditions associated with chronic musculoskeletal pain are back pain, osteoarthrosis joint pain, osteoporosis, rheumatic diseases, and cancer.
The use of cannabis for musculoskeletal pain pre-dates recorded history. The Assyrians, Persians, Chinese and Indians used the cannabis plant as medicine for millennia. Irish physician and inventor Dr William O’Shaughnessy first introduced cannabis research into Western medicine in 1843, writing that cannabis “is extensively employed for a multitude of affections especially those in which spasm or neuralgic pain are prominent symptoms”. Prohibition of cannabis use and cultivation began in 1937 and medicinal cannabis was not available by medical prescription in Australia until November 2016.
‘Medicinal cannabis’ in Australia are pharmaceutical-grade (made to Good Manufacturing Practice standards), highly regulated products containing precise quantities and combinations of, 9 -tetrahydrocannabinol (THC) and cannabidiol (CBD) in oils, capsules, tablets and vaporisers. THC and CBD, the two most common cannabinoids in the cannabis plant, were first described in the 1960s and are partial agonists of the human endocannabinoid system (ECS). The ubiquity of the ECS in all homeostatic body systems has stimulated interest in the ECS’s importance and function and in the medicinal properties of the plant-based phytocannabinoids which mimic the neuromodulating endocannabinoids. However, studies until recently remained scarce as research grants and licensing were difficult for the past 80 years due to its illegality. Medicinal cannabis prescribing is subject to strict regulation by the TGA for appropriate clinical indications, dosing, formulation, length of treatment and stability. Each patient requires individual authority except from specialised authorised prescribers. Australia has a unique opportunity to examine the effectiveness and safety of medicinal cannabis for approved conditions. In many jurisdictions (e.g. Canada, Israel, and most states of the USA) access to the cannabis plant with unregulated concentrations, variable delivery and unknown combinations of hundreds of cannabinoids, terpenes, flavonoids etc, is legal for recreational use or dispensed for medicinal use. Care should be taken in interpreting the outcomes of many systematic reviews as they necessarily conflate studies of unregulated botanicals for medicinal purposes (i.e. recreational cannabis) with studies using pharmaceuticalgrade medicinal cannabis. However, such reviews have demonstrated sufficient evidence for the approval of cannabinoids in management of chronic musculoskeletal pain, particularly in neuropathic pain. Reviews of medicinal cannabis such as Nabiximols (a registered 1:1 ratio of THC/CBD for pain from muscular spasm in multiple sclerosis) are more convincing, demonstrating that medicinal cannabis may have a role in managing chronic pain, particularly neuropathic-type pain, with a response rate of 67% and a 50% improvement in perceived pain scores.
Interestingly, the presence of anxiety and stress were found to be important predictors of response to treatment. Further, surveillance studies have demonstrated that medicinal cannabis has low potential for harm, is well tolerated, and is helpful to patients. Additionally, cannabinoids have the potential for opioid sparing in those with pain. In Israel, 97% of pain physicians prescribe medicinal cannabis and 88% rated opiates more hazardous. Health Quality Ontario in 2018 issued quality standards for prescribing for chronic musculoskeletal pain, stating that opioid therapy should only be
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