Therapeutic uses of cannabis
1997
Summary and recommendations
Arguments in favour of sanctioning cannabis for medical use have been based mainly on anecdotal reports (Grinspoon and Bakalar, 1993). Although many of these case histories sound convincing, and are often moving, they do not by themselves constitute scientific evidence (see Hall et al., 1994). On the other hand, the accumulation of scientific evidence has been hampered by regulations restricting the use of cannabinoids to one clinical indication (nabilone and dronabinol in the UK and dronabinol in the US as anti-emetics in cancer chemotherapy). It cannot be ignored that under these circumstances many normally law-abiding citizens - probably many thousands in the developed world - have resorted to the illegal use of cannabis to alleviate distressing symptoms inadequately controlled by existing drugs. Such therapeutic use should not be confused with recreational misuse.
This report has presented the information available from scientifically controlled trials of cannabis and cannabinoids in patients with various medical conditions, and related volunteer studies. The information is meagre but nevertheless it can be concluded that although cannabis itself is unsuitable for medical use, individual cannabinoids have a therapeutic potential in a number of medical conditions in which present drugs or other treatments are not fully adequate. Long-term effects of chronically administered cannabinoids have not been studied, but present evidence indicates that they are remarkably safe drugs with a side-effects profile superior to many drugs used for the same indications.
There are two mechanisms by which the law could be changed in the UK to allow the prescription of those cannabinoids which are currently controlled under Schedule 1 of the Misuse of Drugs Act as having no medical use. The first involves the World Health Organization recommending to the United Nations Commission on Narcotic Drugs that certain cannabinoids should be rescheduled under the United Nations Convention on Psychotropic Substances so that they could be prescribed as a medicine. As a party to the convention, the UK Government would normally make a corresponding change to the misuse of drugs legislation to allow its prescription in the UK, (although under the terms of the Convention, countries are free to adopt stricter controls than those required by the Convention). This would be the responsibility of the Home Office.
Whilst this is the usual mechanism for affecting such changes, alternatively research-based evidence of the therapeutic benefits of cannabinol or other cannabinoids could be presented to the Home Office and Department of Health who could then consider modifying the Misuse of Drugs Act to allow their prescription by doctors.
The results of this review of research therefore leads the BMA to make the following recommendations:
1. The World Health Organization should advise the United Nations Commission on Narcotic Drugs to reschedule certain cannabinoids under the United Nations Convention on Psychotropic Substances, as in the case of dronabinol. In response the Home Office should alter the Misuse of Drugs Act accordingly.
2. In the absence of such action from the World Health Organization, the Government should consider changing the Misuse of Drugs Act to allow the prescription of cannabinoids to patients with particular medical conditions that are not adequately controlled by existing treatments.
3. A central registry should be kept of patients prescribed cannabinoids so that the effects can be followed up over the long term.
4. The Clinical Cannabinoid Group*, interested patient groups, pharmaceutical companies and the Department of Health should work together to encourage properly conducted clinical trials to evaluate the further potential therapeutic uses of cannabinoids, alone or in combination, and/or in combination with other drugs.
5. The regulation of cannabis and cannabinoids should be sufficiently flexible to allow such compounds to be researched without a Misuse of Drugs Act licence issued by the Home Office.
6. Pharmaceutical companies should undertake basic laboratory investigations and develop novel cannabinoid analogues which may lead to new clinical uses.
7. To prevent misuse patients should be warned to keep these drugs in a place inaccessible to others.
8. In the absence of product licences, information similar to data sheets is required for all preparations of cannabinoids and equivalent compounds even if prepared from natural substances. Standardised patient information should also be prepared after consultation with pharmacists.
9. Research on the clinical indications for medical prescription of cannabinoids should be undertaken. For all the indications listed below (i-vii) further research is required to establish suitable methods of administration, optimal dosage regimens and routes of administration.
i) Anti-emetics
Further research is needed on the use of Delta8-THC as an anti-emetic, the use of cannabidiol in combination with THC, and the relative effectiveness of cannabinoids compared with 5-HT3 antagonists. Further research is needed in other cases of nausea and vomiting such as post-operative.
ii) MS, spinal cord injury and other spastic disorders
A high priority should be given to carefully controlled trials of cannabinoids in patients with chronic spastic disorders which have not responded to other drugs are indicated. In the mean time there is a case for the extension of the indications for nabilone and THC for use in chronic spastic disorders unresponsive to standard drugs.
iii) Pain
The prescription of nabilone, THC and other cannabinoids (including the new more selective synthetic agents such as levonantradol, (-)-HU-210 and others in the process of development) should be permitted for patients with intractable pain. Further research is needed into the potential of cannabidiol as an analgesic in chronic, terminal and post-operative pain.
iv) Epilepsy
Trials with cannabidiol (which is non-psychoactive) used to enhance the activity of other drugs in cases not well controlled by other anticonvulsants are needed.
v) Glaucoma, asthma
Cannabinoids do not at present look promising for these indications, but much further basic and clinical research is needed to develop and investigate cannabinoids which lower intraocular pressure, preferably by topical application (eg eye drops; inhalant aerosols), without producing unacceptable systemic and central nervous system effects.
vi) Stroke and neurodegenerative disorders
The potential of (+)-HU-210 for these indications should be explored through further research.
vii) Immunological effects
Further research is needed to establish the suitability of cannabinoids for immunocompromised patients, such as those undergoing cancer chemotherapy or with HIV/AIDS.
10. Prescription formulations of cannabinoids or substances acting on the cannabinoid receptors should not include either cigarettes or herbal preparations with unknown concentrations of cannabinoids or other chemicals.
11. While research is underway, police, the courts and other prosecuting authorities should be aware of the medicinal reasons for the unlawful use of cannabis by those suffering from certain medical conditions for whom other drugs have proved ineffective.
*The Clinical Cannabinoid Group is chaired by Dr Roger Pertwee. Its membership consists of those planning to set up clinical trials of cannabinoids and it aims to provide expertise, advice and knowledge to clinical researchers to facilitate such research. Contact: Dr Roger Pertwee, University of Aberdeen, tel. 01224 273040; e-mail: rgp@aberdeen.ac.uk