Oncology Pharmacists Should Be Aware of the Benefits, Risks of Cannabis


Cannabis is comprised of over 480 compounds and 70 distinct cannabinoids, but tetrahydrocannabinol (THC) and cannabidiol (CBD) are the 2 most commonly used.

Although cannabis is still considered a Schedule I agent by the Drug Enforcement Administration, many patients with cancer are turning to cannabis products for relief. Because of this, and changing attitudes around marijuana use, oncology pharmacists should educate themselves on the uses and dangers of combining marijuana with chemotherapy, according to a session at the Hematology/Oncology Pharmacists Association 2020 Meeting in Tampa, Florida.

Cannabis is comprised of over 480 compounds and 70 distinct cannabinoids, but tetrahydrocannabinol (THC) and cannabidiol (CBD) are the 2 most commonly used, according to presenter Alyssa Heiden, PharmD, BCOP, clinical oncology pharmacist at Children’s Hospital Colorado. Heiden added that she has seen an increase in the use of cannabis products.

“In my institution here in Colorado, I have seen a lot of cannabis use in patients in recent years,” Heiden said.

In a cross-sectional anonymous survey of 926 adult patients with cancer, 222 respondents said they were active cannabis users according to Heiden. Notably, most respondents said they preferred to get information about cannabis products from their cancer team, but less than 15% actually received this information from their cancer physician or nurse.

Legally, cannabis exists in a gray space. Heiden explained that legalization has been left largely to individual states to decide, and added that pharmacists should stay aware of changing laws. Pharmacists should not recommend a specific source for obtaining cannabis, Heiden said, and should refrain from giving specific instructions on use or obtaining the drug for a patient.

The most important step for pharmacists, Heiden said, is to ask patients about which product they are using or are interested in.

THC is a central and peripheral partial CB1 and CB2 agonist. Based on current research and recommendations, Heiden said its proposed therapeutic effects include nausea and vomiting control, appetite stimulation, pain management, and decreased ocular pressure.

CBD has a low affinity for CB1 and CB2, and works to break down anandamide, GPR55, and TRPV. Heiden said its proposed therapeutic effects include epilepsy treatment, appetite stimulation, and pain management.

Overall, Heiden said cannabis products can have positive effects on some negative aspects of chemotherapy.

  • Controlled clinical trials and anecdotal evidence have supported the use of cannabis for nausea and vomiting. In addition, the FDA has approved dronabinol and nabilone—2 THC-derived drugs for chemotherapy-induced nausea and vomiting.
  • Some evidence supports the use of cannabis products for increasing appetite in patients receiving chemotherapy. Dronabinol is indicated for the loss of appetite due to AIDS.
  • There is limited data supporting the use of cannabis products to treat and prevent peripheral neuropathy from vinca alkaloids, platinum agents, and taxanes. CBD also has notable anti-inflammatory properties.
  • Studies have supported the use of cannabis products as a short-term sleep aid, especially for patients with chronic pain due to cancer.
  • For patients with anxiety, THC may increase their symptoms while CBD can act as an anxiolytic.
  • Notably, Heiden said there is insufficient evidence that cannabis can have anticancer effects in humans.

Despite these potential positive effects, Heiden emphasized that cannabis products can have significant treatment interactions for some cancer drugs. She recommended several resources for understanding these interactions, including the Natural Medicines database, and Memorial Sloan Kettering’s resources.

Aside from drug interactions, significant adverse effects of cannabis can include cardiovascular effects (tachycardia, hypotention, and hypertension), hyperemesis syndrome, bronchodilation, decreased gastrointestinal motility, and sedation.

Heiden also outlined her hospital’s policy as a case study of the various issues health systems should consider when designing a cannabis policy. At Children’s Hospital Colorado, Heiden said any patient who wants to use medical marijuana must complete a release and waiver of liability form. The pharmacist is only involved in ensuring that the method is either oral or topical (inhaled methods are not permitted), and to ensure that patients have a medical marijuana card.

Any dose administered in the hospital must be given by the patient, their legal guardian, or a parent, and the pharmacist must complete a drug interaction check. Heiden added that they have a cannabis consult team to meet with patients and their families.

Finally, Heiden said, it is important to keep an open dialogue with patients.

“I think we need to keep an open mind, and be honest with [patients] so that they can come to us, and be honest with us at any point during their care,” Heiden concluded.


Heiden A. Chemotherapy and Cannabis: Best Buds? Presented at: Hematology/Oncology Pharmacists Association 2020 Meeting: Tampa, FL; March 12, 2020.

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