Medical cannabis should be prescribed only as a last resort for patients with chronic pain as the potential harms caused by side effects may outweigh the benefits, according to an RACGP position statement.
The statement on the medicinal use of cannabis products was issued last month [October] in response to queries from GPs following the legalisation of cannabis prescription in Australia.
The prescription of medical cannabis became legal in Australia from 1 November following the amendment of the Narcotic Drugs Act in February to allow the supply of suitable medicinal cannabis products for the management of painful and chronic conditions.
“GPs are seeing a lot of patients coming in asking for medical cannabis as an option for treatment. A lot say they are consuming amounts already and it’s great for their back pain - it’s quite a significant problem,” said RACGP president Dr Bastian Seidel.
“If you have tried everything else that’s available to you as a medical practitioner and nothing works or there are side effects, using medical cannabis is the last resort to helping your patient in reducing their pain.”
According to the RACGP, the evidence base for the use of medical cannabis is incomplete, particularly around efficacy and long-term safety of cannabis products, and further research was needed.
A spokesperson for the Centre for Medicinal Cannabis Research and Innovation said that, given the uncertainty over prescribing unregistered cannabis products, it was expected that specialists rather than GPs would prescribe cannabis products.
“GPs play an important role in care provision and co-ordination, so it is important that they discuss any prescriptions for cannabis or cannabis products made by a specialist with that specialist, so that treatment goals are clear and the GP can assist the patients in managing any drug-drug interactions that might occur,” she said.
The RACGP is also concerned that patients self-managing pain using inhaled cannabis may not be aware of potential long-term side effects. The college has called for more education of patients and health professionals that medical cannabis is a last-resort for specific categories of illness, and can only be prescribed in rare circumstances after stringent legislative criteria are satisfied.
“We are concerned about the mental and psychological side effects, particularly how it affects the developing brain. There have been no long-term longitudinal studies so if patients are using cannabis, whether it’s inhaled or medical cannabis, we need to monitor them really closely,” Dr Seidel said.
Several international studies have shown that cannabis is effective in relieving neuropathic pain.1,2 Two of the 70 cannabinoids in cannabis, tetrahydrocannabinol (THC) and cannabidiol, have been shown to activate cannabinoid receptors in the endocannabinoid system3 which regulate the release of neurotransmitter and central nervous system immune cells to control pain4.
Cannabis has also been shown to reduce neuropathic pain caused by diabetes5 and multiple sclerosis6.
Australian researchers at the Pain Management Research Institute (PMRI) are testing a range of cannabinoids in the laboratory. Previous research using synthetic cannabinoids found they produced side effects such as cognitive and motor impairments, with no window between the dose required for pain relief and the onset of side effects, said Dr Christopher Vaughan, a PMRI pain researcher from the University of Sydney.
However, much more promising is new basic research that focuses on THC as an additive to first-line treatments for neuropathic pain and also other non-psychoactive cannabis constituents, Dr Vaughan said.
“I’m quite amazed at how well it’s working. It looks like it is synergising the pain relieving effect of the other medications without promoting side effects,” he said.
However Dr Seidel cautioned that community hype around medical cannabis should not lead to rushed approval. “Medical cannabis should be subject to the same regulatory framework and diligence as any therapeutic, and these processes take time,” he said.
Medicinal cannabis - a guide to current laws
- Before products can be prescribed, they must be registered with the Therapeutic Goods Administration or, in rare circumstances, receive special approval from the TGA.
- The registration process requires evidence of testing and efficacy. There are currently no TGA-registered medicinal cannabis products available for GPs to prescribe in Australia.
- Some unregistered pharmaceutical cannabinoids can be obtained by particular patients through the Special Access Scheme. The scheme allows therapeutic goods that are not registered in Australia to be supplied with TGA approval under specific circumstances by a physician with a schedule 8 permit.
- As of August 1, 2016, the Poisons and Therapeutic Goods Amendment Regulation will allow doctors in NSW to apply to the NSW Health Board to prescribe cannabis-based products that are not currently on the Australian Register of Therapeutic Goods. Doctors will need approval from both the TGA and NSW Health before they can prescribe an unregistered cannabis-based product.
- A national regulatory framework for prescribing medicinal cannabis products is currently being developed. Whilst there will be state variation, the intention is to produce a cohesive, national framework that supports and compliments state legislation.
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Content produced by Cirrus Media with an independent educational grant from Pfizer Australia.
1. Jensen B et al. Curr Pain Headache Rep. 2015. doi:10.1007/s11916-015-0524-x2
2. Boychuck, et al. J Oral Facial Pain Headache. 2015. doi: 10.11607/ofph.1274.
3. Fine & Rosenfeld. Curr Pain Headache Rep. 2014 doi: 10.1007/s11916-014-0451-2.
4. Woodhams et al. Handb Exp Pharmacol. 2015. doi: 10.1007/978-3-662-46450-2_7.
5. Wallace, et al. J Pain. 2015. doi: 10.1016/j.jpain.2015.03.008.
6. Rog et al. 2007 Clin Ther.