Home > Cannabis for medical use: a scientific review.

Dillon, Lucy (2017) Cannabis for medical use: a scientific review. Drugnet Ireland, Issue 62, Summer 2017, pp. 9-10.

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Cannabis for medical use: a scientific review1 was launched by Minister for Health Simon Harris TD on 10 February 2017. He described the review as a ‘milestone’ in the development of policy on medicinal cannabis in Ireland.2 The review was carried out by the Health Products Regulatory Authority (HPRA) in response to a request from the Minister in November 2016 for expert scientific advice on the use of cannabis for medical purposes.


HPRA defined the medical use of cannabis3 as ‘a situation where a doctor prescribes or recommends the use of cannabis for treatment of a medical condition in a patient under his/her care’ (p. 9). It convened a group of clinical experts and patient representatives to assist them in carrying out the work. They did not undertake a systematic review of the data on cannabis for medical use. Instead, they reviewed a selection of what they considered to be the ‘main scientific reviews and relevant publications’ (p. 2).4 They also carried out a survey of HPRA’s global regulatory counterparts to explore the situation in other jurisdictions and their policies on access to cannabis for medical use.5


The review covered four main themes:

  • The cannabis products available
  • The regulatory regimes in countries where cannabis was allowed for medical purposes
  • The research on new indications and evidence of efficacy of cannabis for various medical conditions
  • The current legal situation in Ireland and legislative changes required for cannabis to be made available for medical purposes here

This article focuses on elements of the last two themes.


Evidence of effectiveness

Overall, the team found an absence of scientific data demonstrating the effectiveness and safety of cannabis products (p. 1). They also found that most cannabis products available through international access programmes did not meet ‘pharmaceutical quality requirements’ (p. 1). As the regulator of medicines and other health products in Ireland, HPRA’s role is to ensure that any medicines available on the Irish market are ‘safe, effective and of an appropriate quality based on clinical and scientific data’ (p. 7). The authors found insufficient evidence to allow for cannabis products to be authorised as medicinal products (medicines) under this regulatory requirement.

There were a number of complexities involved when examining the evidence base. For example, ‘a major limitation’ (p. 13) was the variation in the formulations of cannabis that had been studied, particularly in relation to the tetrahydrocannabinol (THC) and cannabidiol (CBD) ratio.6 Another was the variety of medical conditions under examination. The potential benefits and risks of cannabis products depend on the product, dose and duration of use, and the patient population. Given the variation in what was explored in the studies, the team found it challenging to draw conclusions regarding the effectiveness of treatment.


Despite these limitations, the team found three medical conditions for which there was ‘some scientific evidence to support the use of cannabis or cannabinoids as a medical treatment in patients who have failed available treatments’ (p. 16). These were:

  • Spasticity associated with multiple sclerosis
  • Intractable nausea and vomiting associated with chemotherapy
  • Severe, refractory (treatment-resistant) epilepsy

However, there was insufficient evidence to support their use for other conditions, including chronic pain.


Access programmes

At the core of the review’s findings is HPRA’s acknowledgement that the Government may decide to make cannabis more readily available on a medicinal basis: ‘The decision to permit access to cannabis for medical use is a societal and policy decision due to the paucity of scientific research, the recreational use of the product and the strong public and patient demand’ (p. 1). Any products or preparations extracted from the cannabis plant that are psychotogenic are currently controlled under the Misuse of Drugs legislation and their medical use is therefore not permitted.7 However, if the Minister for Health considers it to be in the public interest, a specific licence can be granted which allows a doctor to prescribe products containing THC. Any application for a licence must be accompanied by an endorsement from a medical consultant who is responsible for the care of the individual applicant.


The authors argued that if cannabis were to be made more readily available for medical use in Ireland, then it should only be permitted under a controlled access programme for the treatment of patients with a selection of medical conditions. Any programme should be part of a ‘structured process of formal on-going clinical evaluation in a limited number of clearly defined medical conditions’ (p. 6). They advised that the programme be run for an initial period of 5 years and be limited to the medical conditions outlined above. The programme should have the following features:

  • Patients treated with cannabis should be under the care of a medical consultant who has expertise in the condition being treated. He/she would be responsible for the ongoing monitoring of the patient.
  • There should be a central register for patients, doctors and pharmacists involved in the programme, with data collected on the use of cannabis by these patients.
  • Authorised cannabis-based medicines should be the products considered first. If unsuitable, then cannabis products from other countries that have been subject to quality control requirements could be used.
  • Patients should be educated about the correct use of any cannabis product provided, the benefits and risks involved, how to report any side-effects, and the care and safe disposal of cannabis products.
  • Doctors and pharmacists should be supported in their prescribing and dispensing of the products (p. 6). 

Ministerial response to the review

Following the publication of the report, the Minister for Health gave a commitment to establish a ‘compassionate access programme for cannabis-based treatments’.2 His decision was based on the advice of HPRA and the programme will therefore only be accessible to people with one of the three medical conditions outlined above and will require the support of a medical consultant. In addition, the Department of Health has established an Expert Reference Group responsible for developing operational guidelines to facilitate the prescription and supply of medicinal cannabis to qualifying patients.8


1    Health Products Regulatory Authority (2017) Cannabis for medical use: a scientific review. Dublin: Department of Health. https://www.drugsandalcohol.ie/26784/

2    Department of Health (2017) Minister Harris publishes ‘milestone’ report on cannabis for medical use. Available online at http://health.gov.ie/blog/press-release/minister-harris-publishes-milestone-report-on-cannabis-for-medical-use/

3      For the purpose of the report and this article, ‘references to cannabis include cannabis resin and other derivatives from the plant such as oils and other processed plant parts’ (p. 8).

4    The main documents used were: Barnes MP and Barnes JC (2016) Cannabis: the evidence for medical use. London: All-Party Parliamentary Group for Drug Policy Reform; Whiting PF, Wolff RF, Deshpande S, Di Nisio M, Duffy S, Hernandez AV, Keurentjes JC, Lang S, Misso K, Ryder S, Schmidlkofer S, Westwood M and Kleijnen J (2015) Cannabinoids for medical use: a systematic review and meta-analysis. JAMA, 313(24): 2456‒73; Hill KP (2015) Medical marijuana for treatment of chronic pain and other medical and psychiatric problems: a clinical review. JAMA, 313(24): 2474‒83; National Academies of Sciences, Engineering and Medicine (2017) The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research. Washington DC: National Academies Press.

5    Forty countries were contacted and received 28 responses from EU member states and seven non-EU states.

6      The cannabis plant is reported to contain more than 100 plant cannabinoids; those thought to be the most important in terms of their clinical effects are tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is the main psychotogenic component of cannabis.

7      One cannabis-based medicine (Sativex®) has been authorised by the HPRA for use with adult patients with moderate to severe spasticity due to multiple sclerosis (MS). Two other medicines based on the structure of THC were reported to be listed under Schedule 2 of the Regulations: nabilone and dronabinol. As CBD does not have any psychotogenic effects, products containing it alone do not fall under the Misuse of Drugs legislation and its restrictions.

8    Department of Health (2017) Minister Harris announces ‘pivotal step’ on medicinal cannabis access programme: prescribers, patients and pharmacists to draw up guidance for the safe use of cannabis-based treatments for qualifying patients. Available online at https://www.drugsandalcohol.ie/27104/

Item Type
Publication Type
Irish-related, International, Open Access, Article
Drug Type
Cannabis, Prescription/Over the counter
Intervention Type
Treatment method, Alternative medical treatment, Harm reduction
Issue Title
Issue 62, Summer 2017
August 2017
Page Range
pp. 9-10
Health Research Board
Issue 62, Summer 2017

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