The Pulse

Why some doctors are in favour of medical cannabis

by Bianca Nogrady

The politics of medical cannabis may be complicated. But for some people it makes a world of difference in relieving pain, nausea, seizures, and other symptoms.



[Image source: iStockPhoto | Trevor Smith ]

With the recent political debate around medical cannabis trials, you could be forgiven for thinking that the notion was something altogether new.

In fact, cannabis has been used medicinally for thousands of years in India and Asia. It was introduced to western medicine in the mid-nineteenth century by an Irish doctor William O'Shaughnessy, upon his return from service in India, and become a popular therapy around the world.

Even former US president Richard Nixon's 1972 National Commission on 'marihuana' supported studies of its use in the treatment of conditions such as glaucoma, migraine and cancer (although Nixon subsequently ignored his own Commission's findings and instead declared a 'war on drugs').

The criminalisation of marijuana saw it swiftly fall from medical favour. However, it seems that medical cannabis's star is once again rising, with some evidence suggesting it may offer considerable relief in conditions where few other treatments are able to help.

Making people more comfortable

Cannabis's therapeutic benefits stem from the way it stimulates with the body's own method of making us feel good, known as the endocannabinoid system, explains Emeritus Professor of Anaesthesia Laurence Mather, from the Northern Clinical School at the University of Sydney.

"The endocannabinoid system in the body is not a pain relieving system like the endorphin system, like for morphine-type things, it's more a general wellbeing system, and it works by making people feel more comfortable with themselves," Mather says.

"It doesn't ablate pain, it makes the body more accepting."

Cannabis helps with a very specific type of pain that does not appear to respond well to pain relieving treatments, such as opioids or non-steroidal anti-inflammatory drugs (NSAIDS).

"It does not work, for example, in post-operative pain … and in acute pain such as from a surgical incision," Mather says.

However, it is showing considerable promise in treating what is called 'neuropathic pain', which generally refers to pain that stems from diseased or damaged nerves. For example, researchers in the United States are testing the use of cannabis to treat the pain associated with sickle cell disease  a condition in which mutated blood cells can cause lifetime chronic pain that has been described as being worse than the pain of labour or cancer.

No-one's smoking anything It's estimated thousands of Australians are risking arrest by using cannabis for medical reasons. A national clinical trial has been announced but legalisation could be many years away, and then for expensive pharmaceutical drugs only. RN's Background Briefing investigates the science and the politics of medical cannabis.

Stimulating appetite

The appetite stimulating effects of marijuana  more commonly known as 'the munchies'  have also proven useful in countering the bodily wasting associated with a range of conditions from HIV/AIDS to cancer.

"That was observed back in the '60s and '70s, particularly by the recreational users of the time … they noticed the incidence of weight gain was more favourable in those that used cannabis than others," Mather says.

This observation led to the development of a drug called dronabinol, which is a synthetic version of the main psychoactive component of cannabis  tetrahydrocannabinol (THC). This drug is used not only to treat weight loss associated with HIV/AIDS and cancer, but also the nausea and vomiting often associated with cancer therapies.

Other conditions

While THC is the most famous of cannabis ingredients, it is not the only one proving beneficial in the medical arena. Another drug, nabiximols, an oral spray which is available in Australia under the brand name of Sativex, contains both THC and cannabidiol, and is used for the treatment of muscle spasms associated with multiple sclerosis.

Given cannabis's potential to alter our mood, thinking and behaviour, it should come as no surprise that it's also being investigated for treatment of psychological disorders such as post-traumatic stress disorder. A recent US study found a 75 per cent reduction in PTSD symptoms with the use of medical cannabis, and in many US states medical cannabis is approved for use in individuals with PTSD.

There is also growing support for the use of cannabis to treat severe childhood epilepsies, such as Dravet's syndrome, with anecdotal evidence from parents suggesting cannabis drastically reduced the frequency of their children's seizures.

Fewer side effects

Likewise, some argue that medical cannabis could provide a much safer and more pleasant alternative to the existing pain relief options used in palliative care.

"The side effects of many things that are used for treating these conditions such as heavy duty pain and things of that kind  treating them with opioids or treating with NSAIDS  are far more dire than they are from cannabis," says Mather.

"People can die from morphine, they stop breathing; people can die from paracetamol because it buggers their livers, people can die from NSAIDS because it buggers their kidneys, but cannabis doesn't do any of these things."

Like any drug, cannabis has its side effects, although what's interesting with medical cannabis is that the effects most sought after by recreational users are generally the effects most avoided by medical users, says emergency medicine specialist Dr David Caldicott, from the Australian National University and Calvary Hospital in Canberra.

"The product that is beginning to emerge globally is one that is bred and used for largely recreational purposes and so these are strains now which contain a much higher concentration of the psychoactive component, which is THC, and that isn't necessarily the most useful component," says Caldicott.

"Many people who consume this product medicinally actually don't like this effect, they choose strains, say for example in the US, that are much lower in THC concentration and higher in the cannabidiol concentrations."

In parts of the world where medical cannabis is legal, considerable effort has gone into developing strains of marijuana that are carefully tailored for medical use, to reduce the unwanted side effects and boost the more desirable ingredients.

Lack of good data

But medical cannabis presents a conundrum for medical professionals. Its illegality in large parts of the world means most medical users are self-medicating and this also makes it a difficult drug to study in clinical trials.

As a consequence, a significant proportion of medical cannabis research is based on self-reported use and outcomes, rather than large, carefully-designed, randomised trials, says Professor Ian Olver, head of the Cancer Council Australia.

"Probably two decades ago I remember sitting on a panel that reviewed the evidence [for medical cannabis], and in most cases the evidence is anecdotal," says Olver. As a result, he is cautious about the idea of more widespread availability of medical cannabis but acknowledges that there may be some patients for whom it is their only recourse to relief.

"If you've got a patient who's been through conventional therapy and has not responded, you're sympathetic to them if they find something that's worked, but that's quite different to saying something should be widely available for everyday use of pain," he says.

Olver says there is also concern about the possible side effects of smoking marijuana, even for medical purposes, as this could introduce cancer-causing chemicals into the lungs.

However Caldicott says there are other methods of delivery being considered, such as e-cigarettes, which would not only be more palatable for non-smokers but could avoid the potential side-effects of smoking. The active components of cannabis can also be infused into tinctures, which could be a useful option for use in children.

Ultimately, the medical cannabis debate is not about making it widely available for a broad range of health conditions  as currently occurs in many states in the US  but about giving a small number of patients an option where they may have none.

"Medical cannabis is never going to replace paracetamol," says Caldicott.

"We're not talking about the sky falling in, we're talking about a niche market which would be very tightly regulated."