Cannabis is a herbaceous plant belonging to the Cannabaceae family and has two subspecies – Cannabis sativa and Cannabis indica. It is cannabis indica which is the main source of the drug marijuana and various other preparations .
Cannabis usage usually takes the form of smoking herbal cannabis (marijuana) consisting of dried leaves and female flower heads .
Cannabis has 21 chemically-related carbon alkaloids which are called cannabinoids of which the most notable are delta-9 tetrahydrocannabinol (known as THC) and cannabidiol. Cannabinoid receptors are found in distinct areas of the brain and spinal column [3,4].
Cannabinoids act as moderate analgesics with low toxicity and they have a potency several times that of codeine and have a longer duration in the body. These compounds can be addictive or have a complementary effect when used with other drugs .
‘Cannabinoids’ also refer to pharmaceutical quality drugs that act in the same way in the body as cannabis substances. Two such drugs are nabilone, which is THC in a capsule form (available in the UK) and dronabinol which is synthetic THC (available in the US). No cannabinoid drugs are available in Australia  and there has only been a low level of success overseas.
A report prepared in 1998 by the South Australian Drug and Alcohol Council for the Ministerial Council on Drug Strategy concluded that the greatest potential for therapeutic use of cannabis lies in three areas [7 ]:
As an appetite-stimulant, used in conjunction with drugs with anabolic properties to promote lean body mass, good nutrition and exercise,
The management of neuropathic pain, and
The quick relief of nausea, such as associated with some cancer chemotherapy treatments.
A Working Party established by the NSW Government to examine the use of cannabis for medical purposes concluded in its final report (August 2000) that medical conditions for which cannabis may be of medical benefit are [8 ]:
HIV-related wasting and cancer related wasting,
Pain unrelieved by conventional treatments,Neurological disorders including (but not limited to) multiple sclerosis (MS), Tourette’s syndrome and motor neurone disease,
Nausea and vomiting in cancer patients undergoing chemotherapy which does not respond to conventional treatments.
The NSW Working Party on the Use of Cannabis for Medical Purposes also recommended in August 2000 that NSW introduce a compassionate regime to assist those suffering from the range of illnesses identified in their report to gain the benefits associated with the use of cannabis without facing criminal sanctions, pending the development of safer and more efficient methods to deliver cannabinoids .
There are a number of claimed harmful effects of cannabis which include:
effects on memory, learning and cognitive processes;
short-term cardio-vascular effects;
long-term risks of bronchial disease and cancers of the aerodigestive tract;
links to psychotic conditions such as schizophrenia in vulnerable individuals;
effects on the immune and reproductive systems. 
The existing legal framework in Australia prohibits the cultivation of plants containing narcotic or psychotropic substances including cannabis [Australia is a signatory to the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances ]. Cannabis is listed as an illegal drug under Federal Australian law – specifically the Crimes (Traffic in Narcotic Drugs and Psychotropic Substances) Act 1990 and the Customs Act 1901  . It is also encompassed by law under the Customs Act 1901 , the Narcotic Drugs Act 1967 and the Therapeutic Goods Act 1989.
Cannabis is also a prohibited substance under NSW law specifically the Drugs Misuse and Trafficking Act 1985 . An exemption from the provisions of this Act would be needed before any cannabis trial could be conducted in NSW .
Cannabis is not currently approved by the Therapeutic Goods Administration (TGA) for therapeutic use in Australia. Application or notification would need to be made to the TGA to exempt the supply or importation of cannabis from restriction and it is not clear that this can occur .
There is considerable debate as to the optimum delivery of cannabinoids treatment to patients. Smoked cannabis is unlikely to be prescribed in Australia as a smoked plant product will not satisfy the requirements for registration as a ‘therapeutic good’. The synthetic drugs currently registered in the US and UK are not popular nor widely used by eligible patients as the drugs need to be taken orally and the beneficial components are not well-absorbed into the body .
In 1997, the World Health Organisation (WHO) acknowledged the moderate efficacy and safety of THC as demonstrated in a number of experiments (such as reducing nausea from cancer chemotherapy) and other possible therapeutic uses. WHO concluded however that further research was needed on the central and peripheral mechanisms of the effects of cannabinoids (such as on gastrointestinal function and the neuropharmacology of THC) .
The United States conducted an extensive investigation of the medical use of marijuana with the Institute of Medicine (IOM) being commissioned by the White House Office of National Drug Policy to undertake this project in 1999 . The report from the IOM made a number of key recommendations which included:
Research should continue into the physiological effects of synthetic and plant-derived cannabinoids and the natural function of cannabinoids found in the body (not just THC alone), and
Clinical trials of cannabinoid drugs for symptom management should be conducted with the goal of developing rapid-onset, reliable, and safe delivery systems .
Medical cannabis programs exist in various jurisdictions in the United States (Alaska, California, Colorado, Hawaii, Maine, Nevada, Oregon and Washington) .
On 6 June 2005, The United States Supreme Court (Gonzales vrs Angel McClary Raich) upheld the right of the United States Government to enforce a federal law (The Controlled Substances Act) prohibiting the cultivation, possession and use of medical marijuana irrespective of where state laws provide an exemption from prosecution. This effectively overrules the legislation in10 US states where medical marijuana in permitted  . This ruling is a law-enforcement issue rather than a health-related one.
In the United Kingdom, the Select Committee on Science and Technology of the House of Lords in 2001 recommended that clinical trials of cannabis for the treatment of MS and chronic pain should be mounted as a matter of urgency. Further the Committee also recommended that research be promoted into alternative modes of administration which would retain the benefit of rapid absorption offered by smoking without the adverse effects  .
Cannabis-based medicines for treating chronic illnesses such as cancer and multiple sclerosis have been trialed in the UK, however the results to date have had mixed success. A recent study published in The Lancet in November 2003 found patients with multiple sclerosis benefited from using the drug. The report concluded there is enough evidence to warrant licensing the treatment for that illness .
Medical cannabis was permitted in the Netherlands from September 2003 which involves the use of plant-based substances. Two licensed companies grow a special strain to sell to the Dutch Health Ministry which labels and packages the drug into small tubs to supply to pharmacies. Patients are advised to dilute the cannabis into tea or into a spray, as the drug is supplied in the form of dried marijuana flowers  .
Research into cannabis-based medicinal extract products continues with a major pharmaceutical company announcing in May 2003 developments with a whole plant medicinal cannabis extract containing tetrahydrocannabinol (THC) and cannabidiol (CBD) as its principal components. The medicine is administered by means of a spray into the mouth  and is currently under regulatory review by the UK Medicines and Healthcare products Regulatory Agency (MHRA)  .
There is general agreement in many jurisdictions that there is sufficient pre-clinical evidence to justify more extensive controlled clinical trials.
1.“ The Medical Use of Cannabis: Recent Developments” NSW Parliamentary Library Research Service, Briefing Paper No 11/99, p1ff
3. “Of Substance” The National Magazine on Alcohol, Tobacco and Other Drugs, October 2003, Vol 1 No 1, p17
4. The Therapeutic Uses of Cannabis” The United Kingdom Parliament, House of Lords Select Committee on Science and Technology, Ninth Report, 14 March 2001, para 3.1
6. National Drug and Alcohol Research Centre (NDARC) Fact Sheet, Medical Uses of Cannabis.
7. “The Medical Use of Cannabis: Recent Developments” NSW Parliamentary Library Research Service, Briefing Paper No 11/99, p33
8. Report of the Working Party on the Use of Cannabis for Medical Purposes, NSW Government, August 2000, Vol 1, p24.
9. Report of the NSW Working Party on the Use of Cannabis for Medical Purposes, August 2000, Vol 1, page 30, Recommendation 9
10. “Medical Use of Cannabis: recent Developments”, NSW Parliamentary Library Research Service Briefing Paper No 11/99, p.5
“11. The Use of Cannabis for Medical Purposes” Department of the Parliamentary Library, Research Note 2002-2003, no13, 15 September 2003.
12. Report of the Working Party on the Use of Cannabis for Medical Purposes, NSW Government, August 2000, Vol 1, p2o.
14. “Medical Uses of Cannabis”, National Drug and Alcohol Research Centre (NDARC) Fact Sheet,
15. “Cannabis: a health perspective and research agenda” World Health Organisation, Division of Mental health and Prevention of Substance Abuse, 1997, p28ff.
16. The Medical Use of Cannabis: Recent Developments” NSW Parliamentary Library Research Service, Briefing Paper No 11/99, p14
17. “Marijuana and Medicine, Assessing the Science Base” Institute of Medicine, Washington 1999, Recommendations 1 and 2.
18. The Medical use of Cannabis: Recent Developments” NSW Parliamentary Library Research Service, Briefing Paper No 11/99, p15
19. Reuters Health “US court: Government can bar medical marijuana use”. Supreme Court of the United States ‘ http://www.supremecourtus.gov/“
20. The Therapeutic Uses of Cannabis” The United Kingdom Parliament, House of Lords Select Committee on Science and Technology, Ninth Report, 14 March 2001, paras 8.3, 8.4
21. “ Cannabinoids for treatment of spasticity and other symptoms related to multiple sclerosis (CAMS study): multicentre randomised placebo-controlled trial ”, The Lancet, Vol 362, Issue 9395, 8 November 2003
22. “Dutch Approve Cannabis as Prescription Drug” Reuters Health, 1 September 2003.