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Harm reduction tips for medicinal cannabis users

8 Jul 2022
This article was published 24 months ago. Content may no longer be relevant.

Although medically prescribed cannabis has been legal in New Zealand for several years now, we know that most of the estimated 266,000 people using cannabis for medicinal purposes are still doing so illegally – in many cases due to the cost, or because their doctor is unwilling to prescribe.

Not only are those people being pushed towards breaking the law to access their medicine, they are operating in a completely unregulated market where they risk buying unsafe or unsuitable products. So if you’re a patient who is buying your product on the illicit market, how can you stay safer?

Medicinal cannabis advocate, co-founder of Medical Cannabis Awareness NZ, and now Business Development Manager for Medleaf Therapeutics,  Shane Le Brun is one of the most informed people in the country on this subject. And so is Pearl Shomburg, convenor of Auckland Patients Group and a medicinal cannabis advocate, who uses cannabis herself for an auto-immune condition. We asked them both to share some harm reduction tips.


First up, the hairy problem of mould. Often thought of as the ideal climate for cannabis, New Zealand’s humid conditions are also ideal for growing mould and fungus – which is something you really want to avoid in your weed.

Luckily, because cannabis tends to be sold as a dried product, severe mould contamination is actually pretty uncommon. But home-grown cannabis will never be sterile, Shane says. “Failure to keep humidity low will result in an explosion in microbial and fungal growth, and outdoor growing is worse in this regard than indoor growing.”

How dangerous is mouldy cannabis, and how can we avoid it?

Although mould can cause fungal pneumonia, there have been very few reported cases of people getting sick from mouldy weed. But it’s still a genuine risk for patients who are immune-compromised.

Pearl once suffered a severe bout of fungal pneumonia herself from smoking mouldy cannabis. “The worst thing was,” she says, “I was too scared to seek medical help due to fear of police involvement….  I recovered, thanks to my youth and robust health at the time.”

Shane says some moulds can give off carcinogenic toxins, which are tested for in prescription products, including products that meet the Medical Cannabis Quality Standards. But if you’re growing it yourself, you should keep an eye on humidity levels.

“Humidity is critical when a plant is flowering and harvested,” he says. “Failure to keep humidity low will result in an explosion in microbial and fungal growth.”

Correct storage is essential to avoid mould, so he recommends you stay away from Ziplock bags. “Air equals gradual degradation of THC. I’ve seen data on the degradation of THC in flower when exposed to fresh air and it isn’t pretty.  Airtight jars with humidity-regulator packs are the best way to go for cannabis.”

Pearl also advises careful storage, but says fresh is always best, because THC can degrade quickly whether it’s in a glass jar or a Ziplock bag. “A constant supply of indoor-grown flower is best for patients rather than one annual outdoor grow.  I believe, as do others, that outdoor-grown is very special and quite different.  I look forward to future research that will define what those differences are.”

Shane says proper curing is even more important because it will give you a better-quality flower. Poorly-dried Cannabis usually smells of grass (the type you find on your front lawn, not the illicit kind), so that’s a red flag.

Unfortunately, proper curing takes time – generally about a month. In Shane’s opinion, the main culprits are the “larger volume” illicit suppliers, who grow large quantities in warehouses and often cut corners in their rush to get the stuff out the door. “Those high-volume growers or tinny house suppliers almost never do good quality curing.”

Pearl emphasises that most Green Fairies are exceptionally careful growing their plants, and primarily grow them organically. But she agrees there are some – “Goblins,” she calls them – who care more for profit than the patient, and “use the naivety of vulnerable sick patients to continue their trade under the helpful cover of Prohibition”.

“However, most patients have little trouble connecting to Green Fairies and are sometimes given direct contacts by their medical professionals.”

What about pesticides used to grow cannabis?

Pesticides are another story. There are some dangerous pesticides being used in the black market, Shane warns. For example, myclobutanil is commonly used to combat mould in vegetables, and generally that’s considered safe. But it should never be heated or burned, because at high temperature it breaks down to a form of cyanide. “It’s prohibited in tobacco production for that reason, and it should be prohibited in cannabis production too.”

Anyone growing cannabis in large volumes will need to use fungicide, and with no checks or balances required there’s every chance they could be using myclobutanil. “It’s always much safer to source from someone you know, then you can be more sure they’re not cutting corners.”

THC, CBD, indicas or sativas?

As any recreational or medicinal cannabis user will tell you, not all cannabis is created equal.

Cannabis is traditionally divided into three strains: indica, sativa and hybrid. Indica is thought to have a relaxing effect, sativa is more energising and hybrid is – you guessed it – a combination of both. However, some experts believe these terms have become more or less meaningless, and that’s where things get a bit complicated.

Put simply, it all comes down to the interaction between cannabinoids (most commonly THC and CBD), and some other chemical compounds called terpenes. These combine to produce the effects people associate with different strains. But the science is still out on exactly how it all works.

Dr Ethan Russo is a psychopharmacology researcher and medical adviser for Rua Bioscience, and has more international credentials than you could fit on this page. In a recent interview with the US National Library of Medicine he said the indica and sativa labels are misleading, because they don’t categorise the actual biochemical profile of the plant.

“The degree of interbreeding/hybridization is such that only a biochemical assay tells a potential consumer or scientist what is really in the plant.”

Here in Aotearoa, Shane says, the market is so underdeveloped that product differentiation is a bit of a moot point. “I think there is too much emphasis on strains in NZ, when for most people, just accessing better quality indoor-grown is more important.”

In his opinion, any THC strain will offer benefits for the vast majority of people. So if you’re looking for CBD-dominant or balanced strains, you could be worrying about something that’s not only beyond your control, but less important than you think.

On the other hand, Pearl says for some patients it’s useful to understand the different strains. “Indica terpenes offer a sedative, calming effect, while sativa can be much more enervating and uplifting.  Seizure patients do not do well on sativa strains, as the enervating, uplifting effects of sativa on the brain exacerbate seizure activity.”

Because there are no labelling requirements for non-pharmaceutical medicinal cannabis products in Aotearoa, you can’t really be sure of what you are getting unless you have a trusted supplier. If you decide to go this route rather than getting a prescription from a doctor, Pearl recommends talking to a Medical Herbalist, via Auckland Patients Group. “They are specialists in plant medicine, and are very knowledgeable about the interactions of plant medicines and pharmaceutical products.”

For those who want to do further reading on cannabis strains or other issues around medicinal cannabis in a New Zealand context, this MCANZ publication is full of great information.

When shouldn't I use medicinal cannabis? Should I talk to my GP?

Although there are a few contraindications for medicinal cannabis use, Shane says most people using CBD in New Zealand can’t afford a dose that’s high enough to be a problem. 

A history of schizophrenia in the family is one known risk factor, but he says prohibitionists would pitch that as a reason for a blanket ban on anyone with mental health issues using it, which is just factually incorrect. “Many people use cannabis for conditions as varied as PTSD, bipolar or anxiety, particularly when used in moderation.

“Most GPs don’t understand this, so patients would be better going to a specialist cannabis clinic for advice …  Of course, that’s not without problems, as specialists are private and cost extra, but it’s worth it if you want a robust screening process for contraindications.”

Pearl says Medical Herbalists are well trained in this area, and can support patients growing their own, or making their own products using Green Fairy flower.

All GPs can now prescribe a small range of the available products in NZ including flower. However, they are still often hesitant to do so, and sometimes judge the patient as a drug seeker, which can make it harder for them to obtain the legal product they were previously prescribed.

She says better education would help give the GPs confidence to prescribe cannabis products, or to support those patients growing their own or using Green Fairy products.

Will medicinal cannabis interact with other drugs?

Comparing the harm of cannabis versus alcohol ahead of the 2020 cannabis referendum, The NZ Medical Journal stated that  “it is almost impossible to die from a cannabis overdose”.

However, research suggests that using cannabis with some common medications, including blood thinners and drugs used to treat cancer and HIV, may cause significant drug interactions. Shane is of the opinion that these interactions can be overstated, again due to the generally low doses people are taking.

But it’s best to be safe and watch your intake.

The best place to research drug-to-drug interactions is the NZ formulary, a medical resource for GPs which is also open to the public. If you search Cannabidiol + tetrahydrocannabinol interactions you should get a comprehensive suite of risks.  (Note: There is one recent study missing, which assesses the risk of using Warfarin with CBD – here’s a link.)

Dr Geoff Noller, an Otago-based medical anthropologist who is currently researching New Zealanders’ use of medicinal cannabis, is also concerned about drug interactions. He said while it’s true many of the legally-available products are low dose, the illicit market is far more unpredictable. Without regulation, one dose could be significantly different from the next. That’s a potential risk for drug-to-drug interactions, but it’s particularly concerning for patients who are psychiatrically vulnerable.

“This is one reason why the recently passed drug checking legislation is so important. Where possible, those using non-prescribed cannabis-based medicines should attempt to have their medicines checked."

Is vaping better than smoking? And why?

It's a good idea to vape rather than smoking, for the sake of your lungs. Although smoking cannabis hasn’t been directly linked to cancer like it has for tobacco, cannabis smoke can still cause emphysema.  

It’s important to heat cannabis to the right temperature, so you don’t burn it. That’s why vaping is essential – because the devices  allow you to control the temperature.  Most people heat their product to between 180 and 205 – above that, vaporizers will start to trigger a little bit of smoke.

Some of the cheaper vapes aren’t very accurate, but Shane says even a modestly priced dry herb vape is a vast improvement on smoking. Sadly, most vapes are still considered to be a drug utensil under the Misuse of Drugs Act, and are therefore prohibited in New Zealand. A few have been registered and approved as medical device, but these are prohibitively expensive.

Both Shane and Pearl agree that legally available vapes are very accurate, and should be subsidised to give patients control over their health. Until that happens, MCANZ is quietly selling them at a modest price, as a “middle finger” to the MoH ruling.


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