5.1     The main reason for our inquiry is that there are now calls for the law to be changed to permit wider medical use of cannabinoids, and to permit the medical use of cannabis itself. This Chapter reviews the evidence which we have received about current and proposed medical uses for cannabis and the cannabinoids. It is important to distinguish the different substances and preparations; for instance, cannabis leaf must be distinguished from cannabis extract, and whole cannabis from THC. It is also important, though not always easy, to distinguish the various possible routes of administration, e.g. by smoking and by mouth.

Current medical use of cannabis

  5.2     Today in the United Kingdom, medical use of cannabis itself is illegal (see Box 3) but quite widespread. According to the BMA report, "many normally law-abiding citizens—probably many thousands in the developed world" use cannabis illegally for therapy. Most such users smoke their cannabis, but some take it by mouth. The UK Alliance for Cannabis Therapeutics (ACT) know of 200 people in the United Kingdom who have used cannabis for MS (p 29); 53 took part in a recent study of perceived effects of smoked cannabis[18] (Q 262). Clare Hodges writes, "It is impossible to know how many people with MS use cannabis...My impression is that most people with MS do not". A Multiple Sclerosis Society survey produced a figure of one per cent; but the Society believe the true figure to be higher (Q 341).

  5.3     The ACT also know of 50 users with spinal injury, and 20 with other conditions. A survey conducted by the newspaper Disability Now in 1997 among its disabled readers revealed, among 200 respondents, 40 people taking cannabis for MS, 40 for spinal injury, 35 for back pain, 27 for arthritis and 64 for other conditions. IDMU's surveys of 2,794 regular cannabis users have revealed 78 whose main reason for using it is medical (p 244).

  5.4     We have received written evidence (not included in the volume of printed evidence) from four patients suffering from MS (besides Miss Hodges) who report that cannabis has a beneficial effect on their symptoms and call for a change in the law to permit the prescription of cannabis. Dr Fred Schon, a consultant neurologist, described the apparently dramatic improvement obtained by self­medication with smoked cannabis resin by an MS patient who had developed a severe and disabling abnormality of eye movements (p 303). We have also heard from people who have used cannabis against epilepsy, ME and pain, and as an anti-emetic after chemotherapy. Further anecdotal evidence was provided by the Alliance for Cannabis Therapeutics and the London Medical Marijuana Support Group.

  5.5     According to Neil Montgomery, some users of cannabis for medical purposes are also, or have been, recreational users, and their medical use is to some extent conditioned by their recreational experience (p 132). Three of the nine such users who have given us evidence are in this category. An increasing number are growing their own cannabis, "primarily to avoid problems of impurity", or buying in bulk to ensure consistency of dose; either course exposes them to stiffer sentences, if caught, than the frequent purchase of small quantities (cp IDMU p 261). Medical users typically take cannabis as frequently as, but in smaller quantities than, recreational users (Q 567).

  5.6     Use of cannabis for medical purposes is sometimes connived at by the medical professions. Clare Hodges took medical advice before trying cannabis for her MS, and was not dissuaded (p 27). "Over 50 patients have told the ACT that their doctors have recommended that they try cannabis for symptomatic relief" (p 29); and 50 of the 200 respondents to the Disability Now survey said their doctor knew and approved. 100 doctors are associated with the ACT (Q 96). Most medical users tell the Multiple Sclerosis Society that their doctors are "mildly supportive" (Q 341). One user's doctor knows that she uses cannabis for pain relief and is unconcerned. Another took to cannabis for his epilepsy on a doctor's recommendation. On the other hand, a third user's consultant would not support his letter to us, "due to the advances in anti-emetic drugs". According to Dr William Notcutt, a consultant anaesthetist[19], self-medication with cannabis for pain is now common, and "Advising on its use can be part of the pharmacological management of pain nowadays" (p 101, Q 434). Finally, the BMA report on medical use was itself prompted by a resolution in favour of medical use of "certain additional cannabinoids", passed by the BMA's Annual Representative Meeting in 1997.

  5.7     The Government consider that the burden of proof rests on the proponents of medical use of herbal cannabis. As recently as 1 March 1994, the then Home Office Minister referred in a Commons answer to "long-standing advice that cannabis has no recognised medical use" (HC WA 632). Since then, the Government line appears to have softened a little: on 2 July 1997, Tessa Jowell MP, the Minister of State for Health, said that officials were keeping available research under review. "At present the evidence is inconclusive. The key point is that a cannabis-based medicine has not been scientifically demonstrated to be safe, efficacious and of suitable quality" (HC WA 174). On 27 October 1997, Paul Flynn MP put it to George Howarth MP, Under-Secretary of State at the Home Office, that cannabis was already widely used, illegally, by sufferers from MS, cerebral palsy and glaucoma; the Minister replied, "All drugs used for medical purposes have to be scientifically tested. If cannabis succeeds in those tests...the Secretary of State for Health...would be willing to consider allowing medicinal use of it. Unfortunately, as of now, there is no such evidence" (col. 580; see also HL 20 April 1998, WA 192, and HC 5 May 1998, WA 351).

  5.8     The Department of Health say the same in written evidence: "There is insufficient evidence to demonstrate the effectiveness of cannabis as a therapeutic agent at this stage" (p 48). In oral evidence they went a little further: "We very much recognise the importance of research in this area and its potential value, particularly when addressed to the needs of patients for whom we have relatively little else to offer" (Q 167). But MS is not the only condition where conventional treatments are relatively limited in their effects, and the Department warned against allowing the "added frisson" of cannabis to distort the perspective (Q 225).

Advice to medical users

Current medical uses of cannabinoids

  5.11     Although cannabis itself is illegal, certain cannabinoids are in current use in UK medicine, within the law. Cannabinoids have anti­nausea effects, and have been used clinically to suppress the nausea and vomiting associated with chemotherapy in cancer patients. This is the only medical indication for which adequate data from controlled clinical trials exist, mostly from studies in the 1970s with pure THC and the synthetic cannabinoid nabilone, an analogue of THC, which were found to be as effective as prochlorperazine and other anti­nausea agents available at the time. On the basis of this evidence nabilone was licensed and is available as a prescription medicine in the United Kingdom for this indication (see Box 4). However, according to Professor Malcolm Lader of the Institute of Psychiatry, University of London[20] (Q 7), it has been little used. He believes that this is largely due to the fact that more powerful anti­nausea medicines were introduced in the 1980s—the serotonin antagonists ondansetron (Zofran), granisetron (Kytril) and tropisetron (Navoban), which are now widely used in conjunction with cancer chemotherapy (cp Hall p 221 and Appendix 3 paragraph 13). They have the advantage over the water­insoluble cannabinoids that they can be delivered intravenously as well as by mouth, and they are effective in up to 90 per cent of patients. There have been no clinical trials to compare the effectiveness of cannabinoids with the serotonin antagonists (RPharmSoc p 287).

  5.12     This means that cannabis and cannabinoids are likely to be of benefit as anti-emetics only to the small proportion of patients who do not respond to existing treatments, or possibly in the treatment of the delayed stages of emesis which can occur for some days following cancer chemotherapy, and which do not respond well to the serotonin antagonists. Nevertheless, cannabinoids are undoubtedly effective as anti­emetics and more research in this field might explore their use in combination with the serotonin antagonists, help to determine for which patients they are most appropriate, and examine the potential of the allegedly less psychoactive cannabinoid D⁸­THC, for which there have been encouraging preliminary clinical results (Q 74).

  5.13     THC itself (dronabinol—see Box 5) is licensed as an anti-emetic in the USA, but not in this country. The BMA report recommends that it should be licensed here. This would depend on the manufacturer applying for a licence; in the mean time, doctors may prescribe it on an unlicensed basis at their own risk.

  5.14     Dr Notcutt is currently treating patients suffering from intractable pain with nabilone, on an unlicensed basis. He has treated a total of 60 patients with a variety of chronic pain conditions, including MS, cancer, peripheral nerve damage and spinal lesions. As many as 50 per cent have derived some pain relief from nabilone, but a significant number of patients are unable to tolerate the side effects of the drug (unpleasant psychoactive effects and drowsiness) (Q 400) and the overall success rate is about 30 per cent (p 104).

  5.15     Cannabis has been advocated to treat anorexia, but the scientific basis of this remains unclear. In normal subjects cannabis intake is followed about three hours later by an increased appetite ("the munchies"), particularly for sweet foods (Pertwee Q 256). Regular users of cannabis, however, become tolerant to this effect and appetite may even be depressed. According to the BMA report clinical trials have failed to establish any beneficial effect of THC on appetite in patients with anorexia nervosa. However, in controlled clinical trials in patients with advanced AIDS­related illnesses, dronabinol significantly reduced nausea, prevented further weight loss and improved patients' mood. On the basis of such data the US Food and Drug Administration have licensed dronabinol for the treatment of anorexia associated with AIDS; Dr Robson sees this as "the most compelling indication" for cannabis-based medicines (Q 458).

  5.16     There is a concern with regard to the use of cannabinoids in AIDS because of the possible immunosuppressive effects of these drugs (BMA QQ 79, 80, Hall Q 742). Such effects could be damaging in patients whose immune system is already compromised, although there is no evidence of any relationship between cannabis use and the rate of progression to AIDS in HIV­positive men (Robson Q 460).

  5.17     The BMA report recommends that the licensed indications for nabilone be extended to preventing weight loss and treating anorexia in patients with cancer or AIDS, and that dronabinol should be licensed in this country for this indication. As noted already, this would depend on application by the manufacturers; in the mean time, doctors may prescribe "off-label" at their own risk. Dronabinol is a controlled drug, listed in Schedule 2 to the Misuse of Drugs Regulations (see Box 2); so prescription would have to be on the "named-patient" basis defined in the Regulations (see Box 6).

Proposed new indications for cannabis-based medicines

Multiple sclerosis

18   Consroe P, Musty R, Rein J, Tillery W and Pertwee R, The perceived effects of smoked cannabis on patients with MS, Eur. Neurol. 1997, 38, 44. Back
19   Dr Notcutt is a consultant in anaesthesia and pain management at James Paget Hospital, Great Yarmouth, and a senior lecturer at the University of East Anglia. He has extensive experience of the clinical use of nabilone (see Box 4) for the unlicensed indication of pain control. Back
20   Chairman of the Technical Sub-Committee of the ACMD. Back