Sir, – As a professor of pharmacology and therapeutics at NUI Galway, president of the Irish Pain Society, and leader of a research group with a focus for over 16 years on cannabinoids, cannabis-based medicines and the endocannabinoid system, I have followed, with interest, the recent passing of the Cannabis for Medicinal Use Regulation Bill by Dáil Éireann.

The Minister for Health has, quite rightly, commissioned a review of the area of medicinal cannabis by the Health Products Regulatory Authority (HPRA) in advance of further progressing legislation in this area.

There has been a lot written on this topic in the print media over the past few weeks, much of it well-informed, and some less so.

In fact, Ireland has a long-standing connection with this issue, given that western medicine was first introduced to the plant cannabis sativa as a medicine in the 19th century by the physician Sir William Brooke O’Shaughnessy, a native of Limerick.

In 1964, Dr Yehiel Gaoni and Dr Raphael Mechoulam discovered that delta-9-tetrahydrocannabinol (THC) was the main psychoactive constituent of cannabis sativa, sparking a search for its mechanism of action in the body which led to the discovery of two cannabinoid receptors, CB1 and CB2, and a number of marijuana-like substances (endocannabinoids) that are produced throughout our bodies.

We now know from thousands of peer-reviewed scientific publications that the endocannabinoid system plays a key role in regulating physiological processes including pain, stress or anxiety, appetite, learning, memory and cell development.

Multiple laboratory and clinical studies support the effectiveness of cannabinoids for the treatment of a wide range of disorders, including chronic pain, multiple sclerosis, epilepsy and others. Further randomised, double-blind controlled clinical trials looking at larger patient numbers and over longer time frames would certainly be welcome.

Evidence to date suggests that the adverse side-effects of cannabinoids used in a clinical context are mostly mild, and not overtly serious or life-threatening.

We should also remember that cannabis plants can vary considerably, with different strains containing very different contents of THC (the constituent responsible for the “high”), and with over 100 different cannabinoids present in varying amounts across different strains, many of which do not have abuse potential but may still have significant therapeutic potential (eg cannabidiol).

Ireland has already made provision within its legislation to permit the prescription of the cannabinoid medicine Sativex for the treatment of spasticity in multiple sclerosis.

The latest Bill, if enacted, would see further relaxation of our legislation to permit medicinal use of cannabis and other cannabinoid-based medicines.

I do believe that we are moving in the right direction on this for the benefit of the significant number of patients that do not respond to current medicines but may respond well to cannabinoids.

However, as we continue down this path towards legalisation, we should look carefully at, and learn as much as possible from, the positive and negative experience of countries such as Canada and the US that have legalised cannabis for medicinal use in recent years.

We should ensure that the concept of cannabis as medicine is kept separate from its recreational use, and take measures to ensure that use of cannabis among adolescents in particular does not increase, at a time when the brain is still developing and more vulnerable to potential adverse effects of cannabis. We should also ensure that if or when cannabis and cannabinoids are legalised for medicinal use in Ireland, we have proper regulation and testing in place to ensure their standardisation in terms of precise composition and THC content, and testing for impurities and pesticides, so that patients and doctors can feel secure in what they are taking or prescribing.

Under those circumstances, however, there is no strong rationale for treating cannabinoids any differently than, for example, opioid drugs such as codeine or morphine, both of which are derived from a plant (the opium poppy), have been mainstays in modern medicine for decades, have abuse potential, and whose adverse effects, dependence liability and potential for harm are in fact significantly greater than those of cannabinoids.

Moreover, with continued research into cannabinoids, there is enormous potential to develop novel, more effective drugs with fewer side-effects that target the body’s own endocannabinoid system in a more subtle and selective way than cannabis itself.

We have world-leading cannabinoid research ongoing in Ireland currently, supported by funding agencies including Science Foundation Ireland, the Health Research Board and the Irish Research Council, and continuing the tradition established by Sir William Brooke O’Shaughnessy over 175 years ago.

Continued support of this research into cannabinoids and the endocannabinoid system alongside the introduction of medicinal cannabis in Ireland will be key to ensure that we move forward in an informed manner and can lead internationally in this area. – Yours, etc,

Prof DAVID P FINN,

Professor of Pharmacology

and Therapeutics,

National University

of Ireland Galway.