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A Doctor’s Advice: How to Use Cannabis During Chemotherapy

July 2, 2019
(Sopone Nawoot/iStock)

In popular culture, the terms “cannabis” and “cancer treatment” often go hand-in-hand. This idea is backed up by modern scientific research—a growing body of evidence supports the use of cannabis for the treatment of cancer and associated symptoms such as pain, nausea, and loss of appetite.

Unfortunately, lack of cannabis education for physicians coupled with the legal status of cannabis makes many oncologists reluctant to recommend cannabis to their patients. Because of this, patients often use cannabis without informing their doctors.


JAMA: Most Doctors Know Nothing About Cannabis

According to a 2018 survey of cancer patients, one in eight patients reported using cannabis to treat cancer symptoms. In the same study, only 15% of patients agreed with the statement “Cannabis interferes with other medications.”

This is a dangerous misconception. According to Dr. Joseph Rosado, cannabis physician, lecturer, and author of Hope and Healing: the Case for Cannabis, cannabis interacts with every medication that is processed through the liver, including all chemotherapy drugs.

(Courtesy of Dr. Joseph Rosado)

And he should know—to date, Dr. Rosado has treated nearly 400 cancer patients with cannabis medicine. I spoke with Dr. Rosado to learn more about cannabis and chemotherapy drug interactions.

How Does Cannabis Interact With Chemotherapy Drugs?

When cannabinoids such as THC and CBD are consumed orally, they interact with other medications that are processed by cytochrome P450 (CYP) enzymes in the liver. The interaction causes the levels of the other drug to rise, fall, or rise and then fall. Our bodies use CYP enzymes to metabolize 60% of the drugs on the market today, including all chemotherapy drugs and several anti-epileptic drugs, heart medications, and antifungal medications (drugs that ends with “azole”).


A patient’s guide to using cannabis for cancer

Chemotherapy drugs are cytotoxic, which means that they are toxic to all living cells. The goal of chemotherapy is to kill as many cancer cells as possible while minimizing the death of healthy cells. Because of the CYP interaction, patients who use cannabis medicine in conjunction with chemotherapy run the risk of having a different concentration of toxic chemicals in their blood than expected—making cannabis and chemotherapy a potentially dangerous combination.

Can Chemotherapy Patients Use Cannabis at All?

The good news, according to Dr. Rosado, is that cannabis can be used safely in conjunction with chemotherapy treatment. The interactions in the liver can be easily avoided by changing the way you administer your cannabis medicine.

CYP enzyme interactions in the liver mostly occur with oral (pills, edibles, and tinctures) and sublingual administration. “The liver can be bypassed if the mode of administration is changed, for example, using inhalation (vaping, smoking, inhalers), topical patches and creams, or intra-rectal or intra-vaginal routes (suppositories, ovules),” says Dr. Rosado.


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Of these methods, Dr. Rosado recommends inhalation. “It’s a matter of absorption,” he said. “When you inhale cannabis, 100% of the medicine is absorbed within three to five minutes through an exchange of gasses in the lungs. The cannabinoids bind directly to red blood cells, making their way into the bloodstream immediately. Because of this, patients get more bang for their buck with inhalation.”

Dr. Rosado says inhalation is even safer when patients use the acid (non-activated) form of cannabinoids like CBDA—these don’t appear to metabolize in the same way as non-acidic cannabinoids. To ensure that the cannabinoids aren’t activated, Dr. Rosado recommends that patients vaporize cannabis flowers at 131°F (55°C) or lower.

He also recommends vaporization over smoking. Smoking cannabis has negative effects that make it a poor choice for medicinal use.

What About Patients Who Can’t Inhale Cannabis?

Dr. Rosado says that patients should never use oral or sublingual cannabis during chemotherapy treatments. To avoid hazardous interactions, cannabis edibles should not be eaten within 1.5 to 2 hours of treatments. Further, he recommends that patients never use edibles when being treated for liver cancer. Liver cancer greatly reduces the liver’s ability to metabolize cannabis, not to mention the toxicity caused by the chemotherapy.


Can Cannabis Cure Cancer?

If a patient is unable to inhale cannabis, Dr. Rosado recommends a low-temperature tea made from cannabis buds.

Follow this recipe to make a medicinal cannabis tea:

  1. Bring water to a boil, then remove it from the heating element.
  2. Wait for the water to stop boiling. Water boils at 212°F (100°C). The water temperature should be lower than 220°F (105°C) when you add the buds, so the cannabinoids aren’t activated.
  3. Place the cannabis buds in the hot water, cover the pot, and steep for 20 minutes. You can also steep the tea in a French press.
  4. Strain out the buds and your tea is ready to drink.


Whatever method you use to take medical cannabis, always fully disclose any self-medication to your oncologist. Some cancers require more monitoring with cannabis use. For example, THC might affect estrogen levels (the jury is still out). Because of this, doctors pay more attention to the estrogen levels of patients who have hormone-producing cancers (such as ovarian, breast, prostrate, and testicular) and use cannabis.

Karen Getchell's Bio Image

Karen Getchell

Karen Getchell has been a cannabis educator and patient advocate for nearly 20 years. She is the co-founder of Byron's Botanicals, a hemp-derived CBD-infused product manufacturer.

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  • Michele Nitti

    I am extremely confused by this doctors tea recipe since CBD and THC are hydrophobic and are not soluble in water. Maybe I am misunderstanding.

    • Dermy

      Hi Michele, CBD & THC have low solubility in water. For example, 1g of cannabis added to 1L of boiling water and left for 15 minutes will give you about 1mg of THC per 100 ml (see: Hazekamp, A., Bastola, K., Rashidi, H., Bender, J., & Verpoorte, R. (2007). Cannabis tea revisited: a systematic evaluation of the cannabinoid composition of cannabis tea. Journal of Ethnopharmacology, 113(1), 85-90.). Some cannabinoids are more soluble than others. For example, the acid analogues (eg THCA) are more soluble than their neutral forms. If you search Google Scholar for the title of the paper referenced above, you should be able to download the paper.

    • Joseph Rosado

      You’re correct Michele Nitti and good point! They are hydrophobic, the purpose of the tea is to obtain the acid forms, i.e., cbda and thca; both Dr. Dustin Sulak and Ethan Russo promote the use of the tea.

  • Morgan Gritley

    nice to get some info on what and how to use medical mj. thanks.

  • julioinglasses

    Where do I begin?

    My liver cancer is being held in check by a daily dose of Rick Simpson Oil. I had two TACE procedures. After the first one the cancer returned…then, after the second TACE I was advised to not stop RSO application…I didn’t…now I am 24 months in remission, and, I am about to be released from the liver transplant list because my liver is so healthy…this following being Stage 4 cirrhosis! I am down to Stage 1!

    • Alisohn Floyd-Thompson

      God Bless you and thank you for sharing!!!!! I’m a die heart believer RSO cures cancer, no doubt!!!!

  • Dmember

    “The water temperature should be lower than 220°F (105°C) when you add the buds, so the cannabinoids aren’t activated.”

    So for this medical treatment you don’t want activated cannabinoids?

  • viper643

    The oncologist that I recently conferred with was totally ignorant of cannabis as a medicine. I gave him the link to a Leafly article about the interaction of THC and pain blocking drugs . He expressed no interest; so I’m searching for a different doctor. Sadly, the majority of medical doctors are indoctrinated with the Reefer Madness mentality.

  • freewheelinfranklin543

    Allopaths also tell their chemo patients not to take vitamins while on chemo either. And THC isn’t soluble in water. This article sounds like BS. Leafly has gone downhill.

    • Dermy

      See my comment below (answer to Michele Nitti) – a small amount of THC is soluble in water, more so in boiling water. But not very much – looks like about 10mg/L according to the paper I referenced below……

  • freewheelinfranklin543

    Oh! Jeeze! They are going to censor aka moderate my comment. Now I remember why I hardly ever come here anymore.

  • freewheelinfranklin543

    Goodbye. Wont be back!

  • Joseph Rosado

    Pretty much all medications are metabolized via the CYP 450 system and therefore will affect how the medical cannabis is metabolized in the liver when taken orally and/or oro-mucosally. When in doubt, inhale or use topically, intra-rectally or intra-vaginally, although all “bypass” the liver initially, eventually they do make their way to the liver and kidneys, but to a lesser concentration than oral and ori-mucosal.

  • Joseph Rosado

    Should other questions arise, please reach out to me via Thank you

  • F.R.

    Brewing at less than 220°F (105°C)? OK. But how on earth would you even GET the water to 220 deg when it tops out and boils at 212?

    Vaporizing cannabis at 131°F (55°C) or lower? Vaporizing occurs near the boiling point. Cannabinoids simply do not vaporize at that low a temperature.

    If surviver patients’ anecdotal reports are to be considered, daily doses exceeding 500mg of THC and 200mg of CBD are common. Vaporizing that much Cannabis oil isn’t very practical, and at 55°C it’s impossible.

    In-vitro studies showing cannabinoid activity on cancer cells have focused on the decarboxylated “activated” forms. The value of the acidic forms is debatable.

    The interaction of CBD (in particular) via Cyt P-450 was foisted as a theoretical concern. In practice, it’s been reported as quite minor. No harm in avoiding concurrent administration, but like avoidance of vitamin C, it’s mostly alarm-mongering.

    Too much nonsense. This article is below standards. The good doctor may have encountered 400 patients who use small doses of cannabis, and he’s promoting a nice book, but that’s about it.

  • Easy, mix the cannabinoids with olive oil because olive oil is digested by the lymphatic system.

  • When it comes to your health choose wisely. And when it comes to cannabis choose KanaRelief

  • MataH

    Well I suppose the confusion about this article is that it deals with the associated symptoms of cancer medical treatment, such as pain, nausea, and loss of appetite, that’s a completely different program than treating the cancer itself isn’t it?

  • MataH

    Anyone in Australia knowing where to go what to do to get the RSO treatment for bowel cancer?