Medicinal cannabis: uses and side effects
Medicinal cannabis (medical marijuana) is cannabis that has been prescribed by a doctor to relieve symptoms or to treat a medical condition. There are several types of medicinal cannabis (both natural and man-made) that can be accessed in Australia, but access is tightly regulated. Research into the effectiveness and safety of medicinal cannabis for treating various conditions is ongoing.
Cannabis is probably most well known as a recreational drug. Also called marijuana, hash, pot, grass or weed, various parts of the Cannabis sativa plant can be used and taken in different forms. For example, marijuana (the dried leaves and buds of the plant) can be smoked and hashish (the dried plant resin) can be baked into foods (such as cookies) and eaten.
What are the effects of cannabis on the body?
In addition to its mind-altering effects, cannabis has medicinal effects such as pain-relieving, anti-nausea and anti-inflammatory properties. What’s more, when cannabis or cannabis products are used in a controlled way, these medicinal effects can be achieved without the feeling of getting ‘high’ or ‘stoned’.
The Cannabis sativa plant contains up to about 100 different substances called cannabinoids that are involved in the workings of the endocannabinoid system – a communications system in the brain and body. By acting on specific receptors in this system, cannabinoids can influence your immune system, mood, memory, learning, sleep and appetite.
The 2 main types of cannabinoids that have been studied for medicinal use are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD).
- Tetrahydrocannabinol (THC) is the type that can make you feel ‘high’. THC can also relieve pain, reduce muscle spasms and prevent or reduce nausea and vomiting. It also has anti-inflammatory properties and can help stimulate appetite and improve sleep.
- Cannabidiol (CBD) doesn’t have mind-altering properties, so doesn’t cause you to get high. It reduces the psychoactive effects of THC, and may reduce side effects of THC, such as anxiety. CBD may be helpful in controlling seizures and pain. It is also being investigated for the treatment of several other conditions.
Research into several of the other cannabinoids and their possible uses as medicines is ongoing.
What can medicinal cannabis be used for?
Medicinal cannabis (medical marijuana) has been investigated for treating a variety of medical conditions, including:
- chronic pain (ongoing pain);
- neuropathic pain (nerve pain);
- cancer pain;
- nausea and vomiting associated with cancer chemotherapy;
- improving appetite in people with cancer and HIV/AIDS;
- multiple sclerosis; and
- certain types of epilepsy.
Medicinal cannabis has also been prescribed for people with terminal illnesses as part of their palliative care.
Types of medicinal cannabis
Medicinal cannabis may be a synthetic (man made) cannabis product or a natural Cannabis sativa plant extract. Pharmaceutical cannabis preparations include oils, tinctures and other extracts. Both synthetic and natural extract products can relieve symptoms without harmful psychological or THC-related effects.
Types of medicinal cannabis include the following.
- Nabiximols is a standardised cannabis extract containing approximately equal amounts of THC and CBD. The brand Sativex is the only currently available medicinal cannabis registered on the Australian Register of Therapeutic Goods. It is given as an oromucosal (mouth) spray.
- Dronabinol is a synthetic form of THC taken by mouth as a capsule.
- Nabilone is a synthetic cannabinoid with similar actions to THC. It is available as a capsule that is swallowed.
Controlled and standardised herbal cannabis (plant products) can also be used as medicinal cannabis.
How do you take medicinal cannabis?
You can take medicinal cannabis by mouth as a tablet, capsule, oil, liquid or mouth spray. It can also be taken as a nasal spray. Products that are applied to the skin (patches, gels and creams) have been developed, and raw cannabis can be vaporised for medical use, but not smoked.
How is medicinal cannabis different from marijuana?
Medicinal cannabis comes from cannabis that is grown specifically for medicinal and research purposes. While it is now legal in Australia for cannabis to be grown by approved organisations for these reasons, it’s still illegal to grow your own cannabis or to get it from unapproved sources.
Medicinal cannabis is a medical product made by a pharmaceutical company, which means that the quality and amounts of ingredients are known and regulated. When you smoke marijuana, you are exposed to unpredictable levels of cannabinoids and possibly also impurities. Smoking cannabis from unapproved sources (‘street cannabis’) is more likely to cause side effects, and any type of smoking is bad for your health. It is also illegal to use cannabis for non-medical purposes and to take marijuana for recreational use.
Safety and side effects of medicinal cannabis
Medicinal cannabis is carefully formulated, but there is no standard dose that is suitable for all patients or all conditions. So, the dose is usually started low and gradually increased to maximise its effectiveness while minimising the side effects.
The side effects depend on the type of medicinal cannabis used, and can vary from person to person. They may include:
- tiredness or drowsiness;
- nausea and vomiting;
- changes in appetite;
- dry mouth;
- loss of balance;
- convulsions; and
- problems with thinking, memory and concentration.
More severe psychological side effects, including hallucinations, euphoria, confusion, paranoia and psychosis are possible but rare at low doses.
Medicinal cannabis is not recommended for people with current or past problems with mental illness (including anxiety and depression), people with unstable heart disease and pregnant or breastfeeding women.
Depending on the type of medicinal cannabis you take, you may need to avoid driving or operating heavy machinery. Check with your doctor. It is a criminal offence to drive under the influence of drugs.
Before prescribing medicinal cannabis, your doctor will want to check whether you are taking any medicines, as they may interact with the cannabis.
Does medicinal cannabis really work?
While research into its effectiveness is still ongoing, some results have been promising. However, more evidence is needed to show that medicinal cannabis is effective, and which forms and doses are best. At the moment, medicinal cannabis is usually only recommended when other treatments have not been effective.
There is limited evidence that medicinal cannabis has possible benefits for the following conditions.
Relief of some types of chronic (ongoing) pain. For use in chronic pain, most studies have looked at the use of tetrahydrocannabinol (THC) or THC-rich extracts together with other treatments. There is some evidence that medicinal cannabis can help relieve neuropathic pain to some degree, as well as improve sleep. However, there is currently no clear evidence that it improves overall quality of life or functioning.
Relief of some symptoms related to cancer and its treatment. According to the Cancer Council Australia, medicinal cannabis may be of benefit to some people with cancer as an add-on pain medicine in people with moderate to severe pain; to relieve nausea and vomiting in people undergoing chemotherapy; and to improve appetite in people who have had significant weight loss and muscle wasting.
Reducing seizure frequency and severity in people with epilepsy. The strongest evidence is for the use of a particular type of medicinal cannabis (CBD) in children with certain types of epilepsy.
Relieving muscle spasticity in people with multiple sclerosis (MS). The only currently TGA-registered medicinal cannabis product – Sativex – is indicated for use in people with MS who have muscle spasticity (continuous contraction of muscles that causes stiffness and tightness and can interfere with functioning) that has not responded to other treatments.
How to access medicinal cannabis
The use of medicinal cannabis is highly regulated in Australia. Only doctors (not patients) can apply to the Therapeutic Goods Administration (TGA) to access it. Both specialists and general practitioners (GP) can help people access medicinal cannabis.
Ask your doctor whether medical marijuana may be suitable for you. They may be able to help you access it (if you are a suitable candidate) as an unapproved drug through the Special Access Scheme or Authorised Prescriber Scheme. These are programmes that the Australian Government Department of Health is using to help the appropriate people access these medicines. However, access may still be limited in some states and territories.
The other way to access medicinal cannabis is through a clinical trial. Talk to your doctor about whether there are any clinical trials starting that you may be able to enrol in.
Last Reviewed: 30/10/2018
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