Cannabis and cancer: what pharmacists want you to know

pharmacist talking to woman

Cannabis is a drug derived from the cannabis plant. It contains chemicals that have an effect on the brain and body.

Carlo De Angelis and Sweta Bhimani, Odette Cancer Centre pharmacists, have been studying cannabis and its effects for several years, and in particular in preparation for the legalization of marijuana in Canada last year.

“People typically think of cannabis or marijuana for its psychoactive properties — that it makes you high,” Carlo said. “But, cannabis contains hundreds of cannabinoids – chemicals that interact with the endocannabinoid system in our body and alter the way that system communicates with our body and brain.”

Tetrahydrocannabinol (THC) and cannabidiol (CBD) are the cannabinoids found in highest amounts in plant-based products.

As pharmacists, Carlo and Sweta look at cannabis use and its potential for medicinal purposes through the same lens that they view any other drug or medication.

They say they hear many misconceptions about plant-based cannabinoids. It’s your choice whether or not to use cannabis; if you choose to use, Carlo and Sweta have some information and tips:

It’s not a cure for cancer.

There’s no human research data or evidence to show cannabis cures cancer. There’s been a few studies in animals, and you might hear stories online or from a friend, but until there’s fulsome research about this, we must say cannabis is not a cure for cancer.

It may or may not help with side effects of cancer treatment.

There’s a perception that cannabis can help with many cancer-related symptoms and side effects. Again, we need more research and trials.

For example, we hear often that cannabis is a good way to combat chemo-related nausea and vomiting. While anecdotally some people may find this is true, as pharmacists we rely on research evidence. The existing studies look at cannabis versus a placebo. Against a placebo, the cannabis is better at managing nausea/vomiting. But there are no studies that compare cannabis to the current standard of care. We have traditional therapies to prevent and manage chemo-related nausea or vomiting that have undergone rigorous testing and so we encourage people to try those first.

More research is needed.

As mentioned above, we’d like to see more research comparing cannabis to traditional therapies. However, there are challenges when it comes to research, for example ensuring consistency from batch to batch from the same grower or between growers offering a product similar in THC and/or CBD amount. There is also a need for us to understand how to best deliver the cannabis.

If you choose to use cannabis, tell your healthcare provider or talk to a pharmacist.

Cannabis is a legal substance in Canada and so we want to open up the conversation and ensure you are using this drug safely. Cannabis can interfere with other medications so we routinely ask patients if they use cannabis, just as we ask about other drugs, supplements or remedies. A pharmacist can consider your own personal history to assess your risk for adverse effects.

Cannabis can have adverse effects.

Many people think that cannabis never has adverse effects, that is, an undesired harmful effect. This is not true. Ultimately this is a drug, and most drugs have a risk of an adverse effect. Psychosis, anxiety or other negative effects can occur. Some people are more at-risk for adverse affects than others – please talk to your pharmacist.

If you choose to use:

  • Use a licensed vendor. This ensures that the product purchased is free of contamination from pesticides or other illicit substances
  • Say no to smoking or vaping. There’s enough evidence to show these methods of delivery are harmful to your lungs.
  • Talk about it. If you are undergoing cancer treatment (or treatment for another health condition), let your health care team or pharmacist know that you use cannabis.

More resources:

Cannabis and Cancer

About the author


Alexis Dobranowski

Alexis Dobranowski is a Communications Advisor at Sunnybrook.