Indications and clinical justification
An application to prescribe medicinal cannabis can be submitted for any chronic condition that has lasted for three months or longer and has not responded to conventional medical treatment, or has led to intolerable side effects.
Products containing THC are generally not appropriate for patients who:
- Have a history of hypersensitivity to any cannabinoid or products used in manufacture (e.g. sesame oil).
- Have severe and unstable cardiopulmonary disease (angina, peripheral vascular disease, cerebrovascular disease and arrhythmias) or risk factors for cardiovascular disease—THC acts through the CB1 receptors to decrease blood pressure, increase cardiac demand and causes vasodilation (In patients with unstable ischaemic heart disease who smoke cannabis, there is a four-fold increased risk of myocardial infarction in the hour following smoking).
- Have a previous psychotic or concurrent active mood disorder or anxiety disorder.
- Are pregnant/breastfeeding—there are some reports of pre-term labour and low birth weight. Cannabinoids appear in breast milk.
While not preventing prescribing, the following should also be considered by a medical practitioner:
- Care should be taken in prescribing medicinal cannabis products containing THC to patients under 25 due to potential adverse effects on the developing brain. A risk analysis should be undertaken prior to prescribing these products. Severe liver or renal disease.
- Drug dependence, including nicotine and heavy users of alcohol.
- Other medications especially other sedatives such as opioids and benzodiazepine.
- Paediatric and elderly patients—little is known about how these patient groups react to cannabis. As metabolism in the elderly is slower it is likely they will be more sensitive to the pharmacological effects of cannabis. Treatment should, therefore, be commenced at very low doses and adjusted slowly.
Before applying for TGA approval, a comprehensive clinical assessment needs to be onducted, identifying the risk factors that need to be addressed. This should include:
- Presenting symptoms and underlying diagnosis
The symptoms and/or disease for which the medicinal cannabis product is being considered.
- Past medical history
In particular, cardiovascular disease, liver disease and renal disease.
- Medication review
Treatments that have been tried and have failed; as well as the length of time the treatments were trialled and the reasons for ceasing.
- Mental health history
History of mental illness, particularly schizophrenia.
- Family health history
Including mental health, particularly a family history of schizophrenia.
- “At risk” behaviours
Focusing on those associated with drug dependence and substance abuse disorder. While previous cannabis use may not be a contraindication, care should be taken to manage the risk of dependence. Attention should be paid to histories of nicotine dependence (may contribute to patient smoking product), alcohol dependence abuse, and previous illicit drug use
- Social history
Social and family support for the use of a medicinal cannabis product. Consideration should be given to family responsibilities such as caring for young children, child safety, employment (especially where it involves driving or operating machinery), “at risk” living conditions and the risk of falls in older patients;
- Physical investigations as appropriate
These are left to the medical professional’s discretion.
Monitoring during trial period
Once established on a dose, a monthly review is recommended as a minimum.
At each review the medical practitioner should ensure the following areas are covered: symptom control, adverse events, aberrant behaviour, records (SAAR):
As medicinal cannabis is an unapproved medicine, it is important that patients are reviewed regularly to ensure efficacy and to manage any adverse events. We suggest that a monitoring program similar to that used with opioids would be clinically useful.
- Symptom control
is the product improving the patient’s symptoms? For example, are they eating better, experiencing less nausea and vomiting, have improved pain management and spasticity or evidence of fewer seizures?
- Adverse events
Are they reporting any side effects? For example, are there any signs of drug-drug interactions that may require adjustment of the product or the other medications?
- Aberrant behaviour
Are there concerns that the patient may be on-selling their product? For example, are they using more than prescribed at any one time?
it is important to keep adequate records, especially as medicinal cannabis is an unapproved medicine.
Initial treatment plan
We suggest an initial treatment plan involving a four to 12-week trial period during which the effectiveness of the therapy can be assessed.
The plan should clearly indicate:
- Treatment goals for medical cannabis use
These need to be clearly documented and discussed with the patient, related to the symptoms being treated and ideally be measurable.
- Patient-specific supportive documentation from a specialist
- Risk management processes
Controlling the frequency of dispensing, for example, if there are concerns that a patient may self-escalate their dose.
- Monitoring arrangements
Weekly/fortnightly/monthly reviews, blood tests, specialist reviews, other investigations (as needed) for the medical condition and/or symptoms being treated.
- An exit strategy
For situations where the medication is not helping manage the symptoms or the goals of treatment are not reached.
- That informed consent has been obtained
This includes that the patient has been provided with information about the medicinal cannabis product, possible side effects and treatment goals, and that treatment will be discontinued if the benefit has not been demonstrated. The patient must also be informed they cannot drive with THC in their system and should wait five days after dosing before driving.
Dosing of medicinal cannabis is highly individualised and relies on titration of the product following the rule of thumb "start low, go slow". Finding the right dose, where the therapeutic effect is maximised and adverse effects are minimised, requires patients and doctors to work together.
More information on dosing and titration can be found on the Products and Titration page, or if you have questions about our product mix and advisable dosing, you can contact us. Further information on conditions medicinal cannabis can be effective in treating can be found here.