There has been much interest in the use of medicinal marijuana since the Australian government passed laws allowing the cultivation and manufacture of cannabis for medicinal purposes.
Currently, there is limited evidence about the effectiveness of cannabis and its derivatives for use in different medical conditions. There is also little known as to the most suitable and safe doses of individual products.
This is why, with the exception of one extract (nabiximols), medicinal cannabis products do not appear on the Australian Register of Therapeutic Goods (ARTG) and, as in most other countries, are not available as registered prescription medicines.
For a product to be registered on the ARTG, a sponsor (usually a company) would need to submit a dossier of scientific evidence to the Therapeutic Goods Administration documenting the clinical efficacy, safety and manufacturing quality of that product.
Currently, the Australian Government does not subsidise the cost of medicinal cannabis products through the Pharmaceutical Benefits Scheme (PBS).
Access to medicinal cannabis
Medicinal cannabis can only be prescribed by a registered medical practitioner.
Before prescribing it, the doctor will assess each patient to decide if the treatment is appropriate for their condition and their individual circumstances. The doctor will take a full medical history and a family health history. The doctor will also consider the patient’s current medications and identify any current or previous problems with drug dependence and substance abuse.
Doctors must apply and obtain approval under the applicable state or territory laws to prescribe a medicinal cannabis product to a patient, where relevant. Rules relating to these products vary between states and territories and could affect whether or not you can be prescribed particular medicines in your state or territory.
A variety of products are currently available through import from Canada or Europe. These include raw (botanical) cannabis, which for medicinal purposes should be vaporised but not smoked, cannabis extracts in oils, and solvent extracts such as tinctures, and oro-mucosal sprays. Some products for trans-dermal application (patches or topical application of gel or cream) have also been developed.
Similar products for medicinal use, manufactured from locally grown cannabis, are expected to become available during 2018.
Doctors rely on scientific evidence to make informed decisions about the best medications for their patients. For medicinal cannabis, the amount of evidence is currently limited and the products, doses and research methods used vary between studies. This makes it difficult to come to any firm conclusions about how best to use particular products.
There is also not much information available to help doctors determine the most appropriate and safe doses while minimising potential side effects.
As there is limited scientific evidence to support the use of medicinal cannabis in most conditions, and in many cases the available evidence is for its use together with other medicines, it should be used only when approved treatments have been tried and have failed to manage conditions and symptoms.
Side effects of medicinal cannabis
Like all prescription medicines, medicinal cannabis products can have side effects. The extent of effects of these can vary with the type of product and between individuals.
Tetrahydrocannabinol (THC) and cannabidiol (CBD) are two types of cannabinoids found naturally in the resin of the marijuana plant, Cannabis sativa.
The known side effects from medicinal cannabis treatment (both CBD and THC) include fatigue and sedation, vertigo, nausea and vomiting, fever, decreased or increased appetite, dry mouth, and diarrhoea.
THC (and products high in THC) has been associated with convulsions, feeling “high” or feeling dissatisfied, depression, confusion, hallucinations, paranoid delusions, psychosis, and cognitive distortion (having thoughts that are not true).
• Patients should not drive or operate machinery while being treated with medicinal cannabis. In addition measurable concentrations of THC (the main psychoactive substance in cannabis) can be detected in urine many days after the last dose. It may take up to five days for 80 to 90 per cent of the dose to be excreted. Drug-driving is a criminal offence, and patients should discuss the implications for safe and legal driving with their doctor.
• Medicinal cannabis is not appropriate for people with an active or previous psychotic or active mood or anxiety disorder; women who are pregnant, planning to become pregnant or breastfeeding; and people with unstable cardiovascular disease.
• Patients with neurological conditions may be more likely to experience negative effects from medicinal cannabis.
More research is needed
There is a significant need for larger, high-quality studies to better explore the potential benefits, limitations and safety issues associated with medicinal cannabis treatment across a range of health conditions and symptoms.
As this new evidence emerges over time from doctors, clinical trials and other research, the Australian Government will progressively update the guidelines for both doctors and patients.
For more information visit the Department of Health Therapeutic Goods Administration website at www.tga.gov.au
Therapeutic Goods Administration (TGA). (2018). Guidance for the use of medicinal cannabis in Australia: Patient information. Available at: https://www.tga.gov.au/publication/guidance-use-medicinal-cannabis-australia-patient-information