Medical Cannabis in Chronic Pain Management: Balancing Therapeutic Benefits with Addiction Risks
Interview with Dr. Ferghal Armstrong
Read time: 5-6 mins
Insights from addiction medicine specialist Dr Ferghal Armstrong on navigating cannabis use disorder and optimising patient outcomes.
When Australia legalised medical cannabis in 2016, healthcare professionals grappled with understanding and applying the therapeutic effects of medical cannabis with cautious optimism. Fast forward nearly 10 years, and practitioners are navigating a more nuanced view of the potential harms. Dr Ferghal Armstrong, a GP and addiction medicine specialist, provides insights and clinical perspectives on the complexities of the plant-based medicine terrain, particularly regarding cannabis use disorder (CUD) in legitimate medical users.
"I never really took cannabis seriously when I was a GP," Dr Ferghal explains. "I didn't really see what the harm was until I started training in addiction medicine. Then you do really become acquainted with the harms."
This shift in perspective highlights a growing challenge facing Australian healthcare and the broader medical cannabis community: discerning when medical cannabis becomes problematically used and how to maintain therapeutic benefits while minimising addiction risks.
Medical Cannabis Efficacy may be comparable to opioids
Medical cannabis demonstrates efficacy in chronic non-cancer pain management, with studies showing 30-50% pain reduction, arguably comparable to opioid therapy outcomes. This evidence base has led the Therapeutic Goods Administration (TGA) to approve medical cannabis prescribing for chronic pain conditions under Special Access Scheme and Authorised Prescribers.
"There is as good evidence for the use of medical cannabis as there is for the use of opioids," Dr Ferghal notes, emphasising that both treatments remain somewhat controversial within medical circles.
Mechanism of Action
Medical cannabis works through the endocannabinoid system, utilising what Dr Ferghal describes as "on-demand retrograde signalling." THC binds to presynaptic receptors, inhibiting neurotransmitter release and effectively "turning down the volume" on pain signals.
"Think of a radio," he explains. "You can hear the low volume even when it's turned to silent, it's still on. So, you can choose to turn it up and ratchet up the volume. It's the same with pain. Amplifying or deamplifying is equivalent to turning the volume up and down, and cannabinoids (endogenous or exogenous) will turn down the volume button. Cannabis dampens down or deamplifies the effect of neurotransmission pathways, modulating the experience of chronic pain."
This mechanism differs fundamentally from opioid pathways, offering an alternative approach for patients who haven't responded well to traditional pain management strategies.
Understanding Cannabis Use Disorder in Medical Users
Diagnostic Challenges
Current diagnostic criteria for cannabis use disorder present unique challenges when applied to medical cannabis users. Unlike prescription opioid use disorder, you cannot use tolerance and withdrawal to diagnose prescription opioid use disorder. Still, you can use tolerance and withdrawal to diagnose prescription medicinal cannabis use disorder.
“So by that definition, roughly a third of people who use medical cannabis regularly will end up with a diagnosable cannabis use disorder," Dr Ferghal explains. "But that includes people who are physiologically dependent but only using as prescribed."
“Let me give you an example by counterpoint. For me to diagnose prescription opioid use disorder, I cannot use the criteria of tolerance and withdrawal as part of my minimum two out of 11 criteria. It's very reasonable for me as a doctor to give a little old lady 20 milligrams of Endone a day for her back pain and for her to use those drugs only as prescribed without any illicit or aberrant use.”
He continues, “She becomes tolerant to the endone and when she accidentally forgets to bring her pills on holiday to see her grandchildren, she then goes into opioid withdrawal.” This would not count as a legitimate diagnostic criteria for prescription opioid use, yet it would if the medication was cannabinoid based.
This diagnostic complexity means that many legitimate medical users may be classified as having CUD despite appropriate medication use, creating a significant clinical and ethical concern.
Risk Factors and Vulnerable Populations
Three key groups face elevated risks for developing problematic cannabis use:
Young Adults (Under 25): Brain development continues until approximately age 25, making younger users particularly vulnerable to addiction and cognitive impacts.
Mental Health Conditions: Patients with anxiety, depression, or other psychiatric disorders show increased susceptibility to cannabis dependence.
Previous Addiction History: Individuals with previous substance use disorders face higher risks of CUD when prescribed medical cannabis.
"I think there is an understandable backlash for prescribing potent Category 5 medical cannabis products to anyone under 25," Dr Ferghal observes, highlighting growing concerns about high-potency products in vulnerable populations.
The High-Potency Problem
Modern medical cannabis products bear little resemblance to cannabis from previous decades. High-potency extracts and flowers with THC concentrations exceeding 20%, even 30% have become commonplace, while CBD content has dramatically decreased.
"I remember data on illicitly sourced cannabis from the 1990s, there was a bit of THC and a bit of CBD," Dr Ferghal notes. "Compare that to illicitly sourced cannabis now, there's practically no CBD."
This shift toward high-THC, low-CBD products potentially reduces therapeutic benefits while increasing addiction and adverse event risks, including psychosis and dysphoria.
Category 5 Concerns
Dr Fergal empathises with concerns about the misuse of the medical cannabis system and the active debate around banning Category 5 flower products. Reflecting on patients requesting high-potency smoked flower for conditions like anxiety, he shares:
“I just don't believe that anxiety is appropriately treated with all-day, every-day application of two grams of Category 5 flower. And I don't believe that depression is appropriately treated in that regard as well. I think we need to be clear about what benefit we're trying to achieve if we're not going to throw the baby out with the bathwater.”
Safe Prescribing Practices
Risk Assessment Framework
Dr Ferghal’s insights boil down to a comprehensive approach to medical cannabis prescribing where the following guiding principles shape his application of this plant-based medicine.
Contraindications: Avoid high-THC products in patients under 25, those with active ischemic heart disease, psychotic risk factors, or addiction vulnerability.
Universal Precautions: For high-risk patients, implement regular monitoring, including:
Frequent clinical reviews
Assessment for illicit cannabis co-use
Evaluation of functional outcomes
Dosing Considerations
Appropriate dosing remains contentious, with Dr Ferghal suggesting maximum daily limits of 500mg for flower products, though acknowledging some practitioners prescribe up to 2 grams daily.
He says of patients requesting high daily doses for conditions like anxiety. "It's very easy to use two grams of flower daily if you've got cannabis use disorder."
Treatment Approaches for Cannabis Use Disorder
Emerging Therapeutic Options
Unsurprisingly to some, CBD shows promise in treating cannabis use disorder, with an Australian study indicating 400mg daily CBD may help reduce problematic cannabis use. This approach offers the potential to maintain therapeutic activity of cannabinoid medicine while addressing addiction concerns.
"There's emerging evidence for CBD in the management of cannabis use disorder," Dr Ferghal notes the irony of using one cannabis component to treat problems caused by another.
Integrated Care Models
Successful management requires addressing underlying factors contributing to cannabis dependence, including trauma, ADHD, and psychosocial stressors. Dr Ferghal identifies trauma and ADHD as primary drivers of substance use disorders, emphasising the need for comprehensive treatment approaches.
Future Directions
Medical cannabis represents a valuable therapeutic tool for chronic pain management. However, the significant risk of cannabis use disorder is significant and demands careful patient assessment, appropriate prescribing practices, and ongoing monitoring.
Clinical Practice Evolution
As medical cannabis becomes more mainstream, healthcare providers need enhanced training in:
Addiction risk assessment
Appropriate product selection
Monitoring protocols
Refined diagnostic criteria for medical cannabis use disorder
Effective intervention strategies for problematic use
As Dr Ferghal concludes, "We need to be clear about what benefit we're trying to achieve. I do believe that the system is being misused, and vulnerable patients are being harmed because of a lack of screening and understanding."
Disclaimer: This article is for educational purposes only and should not replace professional medical advice. Healthcare professionals should consult current TGA guidelines and clinical evidence when making prescribing decisions.
References
Mücke, M., Phillips, T., Radbruch, L., Petzke, F., & Häuser, W. (2018). Cannabis-based medicines for chronic neuropathic pain in adults. The Cochrane database of systematic reviews, 3(3), CD012182. https://doi.org/10.1002/14651858.CD012182.pub2
van de Donk, T., Niesters, M., Kowal, M. A., Olofsen, E., Dahan, A., & van Velzen, M. (2019). An experimental randomized study on the analgesic effects of pharmaceutical-grade cannabis in chronic pain patients with fibromyalgia. Pain, 160(4), 860–869. https://doi.org/10.1097/j.pain.0000000000001464
Almog, S., Aharon-Peretz, J., Vulfsons, S., Ogintz, M., Abalia, H., Lupo, T., Hayon, Y., & Eisenberg, E. (2020). The pharmacokinetics, efficacy, and safety of a novel selective-dose cannabis inhaler in patients with chronic pain: A randomized, double-blinded, placebo-controlled trial. European journal of pain (London, England), 24(8), 1505–1516. https://doi.org/10.1002/ejp.1605
Bhardwaj, A.K., Mills, L., Doyle, M. et al (2024). A phase III multisite randomised controlled trial to compare the efficacy of cannabidiol to placebo in the treatment of cannabis use disorder: the CBD-CUD study protocol. BMC Psychiatry 24, 175. https://doi.org/10.1186/s12888-024-05616-3
Dr Ferghal Armstrong is a distinguished specialist in addiction medicine and a general practitioner who combines clinical excellence with innovative medical education. Holding fellowships from both the Royal Australian College of General Practitioners (FRACGP) and the Australasian Chapter of Addiction Medicine (FAChAM), along with membership of the Royal College of General Practitioners (MRCGP), Dr Armstrong currently serves as an Addiction Medicine Specialist at Healthscope and Turning Point Eastern Treatment Services in Victoria. As Co-Founder and CEO of Meducate since 2018, he has revolutionised continuing medical education by creating accessible, technology-driven training programmes for healthcare professionals globally. His extensive experience includes founding and directing the Black Fish Medical Clinic for eight years, serving as a MATOD trainer with the Royal Australian College of General Practitioners since 2018, and providing pharmacotherapy mentorship across various health networks in Victoria. With additional qualifications in skin cancer medicine, dermoscopy, and various medical specialties, Dr Armstrong brings a comprehensive approach to patient care while advancing the field through education, having authored the "Addiction Ebook series" and developed specialised courses on addiction treatment and pharmacotherapy that serve healthcare professionals worldwide.
Disclaimer: This information is shared with a global readership for educational purposes only and does not constitute medical or business advice. All patient-related information has been de-identified OR fictional to protect privacy. Nothing in this article is intended to promote the use or supply of medical cannabis to members of the public.
