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Irish Pain Society Support Cannabis for Chronic Pain

On the 10th of February 2017, Minister for Health, Simon Harris, announced that he has decided to establish a compassionate access programme for cannabis-based treatments in Ireland. The announcement followed the publication of the Health Products Regulatory Authority’s (HPRA) report entitled “Cannabis for Medical Use – A Scientific Review”. The HPRA report advised that, if a policy decision is taken to permit cannabis under an access programme, it should be for the treatment of patients with:

  • Spasticity associated with multiple sclerosis resistant to all standard therapies and interventions
    whilst under expert medical supervision;
  • Intractable nausea and vomiting associated with chemotherapy, despite the use of standard antiemetic regimes whilst under expert medical supervision;

Severe, refractory (treatment-resistant) epilepsy that has failed to respond to standard
anticonvulsant medications whilst under expert medical supervision.

The HPRA report also advised that patients accessing cannabis through the programme should be under the care of a medical consultant and that medical information and utilisation data should be kept on a central register. Overall, the Irish Pain Society considers the HPRA report to be a well-researched, well-written and important contribution to the debate on medical cannabis and cannabinoids and the HPRA should be commended for preparing such a thorough report at relatively short notice.

Controversially, however, the HPRA report recommended against the use of medical cannabis for the treatment of chronic pain. The Executive Committee of the Irish Pain Society, a non-profit organization comprised of multidisciplinary healthcare professionals dedicated to scientific, educational and clinical aspects of chronic pain management, disagrees with this aspect of the HPRA report.

The HPRA’s recommendation against chronic pain was made despite an acknowledgement within
their report that chronic pain is the most researched indication for cannabinoids, and despite the
fact that the majority of clinical studies, meta-analyses and systematic reviews cited in the HPRA
report conclude that cannabis or individual cannabinoids afford moderate to substantial benefit
to patients with chronic pain. Indeed, three of the most thorough and exhaustive scientific reviews
to have been published in recent years all conclude that there is strong, high-quality evidence of a
substantial or conclusive nature that medical cannabis or cannabinoids are efficacious in chronic pain
in adults. The current evidence base in support of efficacy of cannabinoids in chronic pain is without
doubt stronger for chronic pain than for some of the other indications recommended within the HPRA

Four reasons for not supporting the inclusion of chronic pain as a specified medical indication for
medical cannabis and cannabinoids were given within the HPRA report as follows:

  1. the causes of chronic pain are diverse and a suitable patient population or clinical indication for
    treatment with cannabis cannot be defined, due to the complexity and variety of chronic pain
  2. physical, emotional, social, spiritual and other subjective factors inform the individual pain
    experience, making it difficult for a doctor to objectively assess the effectiveness of treatment;
  3. there are a large number of authorised medicines that are of proven effectiveness, and other
    non-pharmacological treatments available to treat the many factors involved in chronic pain; and
  4. chronic pain is common, and the potential use of cannabis-based medicines by a large number
    of patients, raises concerns about misuse and diversion into the wider community.

Regarding the first reason, the causes of chronic pain can be diverse but we now know that peripheral and central sensitisation are the neurobiological mechanisms underlying most types of chronic pain and these mechanisms are reduced by cannabinoids. Moreover, some clinical studies have in fact shown efficacy of cannabis or cannabinoids in specific chronic pain indications or syndromes (e.g. specific types of neuropathic pain, cancer pain and others). Furthermore, the cannabinoid oromucosal spray nabiximols (Sativex®) is licenced in Canada for adjunctive treatment of neuropathic pain in multiple sclerosis, not just spasticity, and also for severe cancer pain, and many other countries around the world, including a number of European countries and a majority of US states over the past 5 years, have now authorised medical cannabis for chronic pain.

Regarding point two, it is certainly the case that many factors can influence the individual pain
experience, as is true for many disorders (including the three indications recommended within the
HPRA report). But a highly trained pain specialist/consultant would be able to assess the effectiveness
of a particular treatment. If that were not the case, and we could not have confidence in the ability of
our medical experts to objectively assess the effectiveness of treatment, then it would not be possible
to justify prescribing any pain medications to patients with chronic pain.

Regarding the third cited reason, many patients have intractable chronic pain. Indeed, 40% of patients
with chronic pain in the landmark Pain in Europe study reported that the management of their pain is
inadequate. This fact, along with the significant adverse side-effects of currently available analgesics,
difficulty in accessing non-pharmacological treatments, and the epidemic scale of the chronic pain
problem (~ 1in 5 people in European countries, including Ireland, at a cost of €5.34 billion per year to
the Irish economy – 2.86% of GDP), means that chronic pain remains a major unmet clinical need.

Finally, regarding point four, the Irish Pain Society believes that the very high prevalence of chronic
pain is all the more reason to do as much as possible to make new treatments such as cannabinoids with proven efficacy and fewer serious adverse effects available to patients. The concerns about misuse and diversion into the wider community, while understandable, are not unique to cannabis/cannabinoids – they also apply to opioids which have been mainstays in pain treatment for decades. In fact, cannabis has significantly less abuse potential than many opioids and significantly less risk of overdose. Moreover, these concerns could be mitigated to a large degree if the authorisation stipulated that only pain specialists/consultants could prescribe cannabis medicines for chronic pain (as the HPRA report recommends for multiple sclerosis, epilepsy and chemotherapy-induced nausea).

Thus, the view of the Executive Committee of the Irish Pain Society is that medical cannabis or
cannabinoid-containing medicines/products could be prescribed, initially by a pain
specialist/consultant only, to any patient with chronic cancer or non-cancer pain that has failed
to respond adequately, or has experienced an unacceptable level of adverse side-effects, to other
analgesic medications, whilst under expert medical supervision. We would also emphasise the
importance of ensuring appropriate regulation and quality of the prescribed product(s) so that
patients and doctors can proceed with confidence.

Importantly, the HPRA report was very supportive of further research within Ireland and internationally
on medical cannabis and cannabinoids, including for chronic pain, and this support is welcomed by the
Irish Pain Society. Continued support of such research into cannabinoids and the endocannabinoid
system alongside the careful, controlled and regulated introduction of medical cannabis in Ireland for
chronic pain will be key to ensure the best outcomes for patients.

Professor David P. Finn, NUI Galway, President of the Irish Pain Society (on behalf of the
Executive Committee of the Irish Pain Society;