"When we think of drug interactions, specifically, the National Cancer Institute actually defines this as a change in the way a drug acts in the body when taken with certain other drugs, herbals, or foods or when taken with certain medical conditions. Drug interactions may cause the drug to either be more or less effective or cause effects on the body that are not expected," Carissa Ganihong, PharmD, BCOP, oncology and bone marrow transplantation clinical pharmacist at Hackensack University Medical Center in New Jersey, told Jaime Weimer, MSN, RN, AGCNS-BS, AOCNS®, manager of oncology nursing practice at ONS, during a conversation about interaction pathways.

Music Credit: "Fireflies and Stardust" by Kevin MacLeod

Licensed under Creative Commons by Attribution 3.0

Earn 0.5 contact hours of nursing continuing professional development (NCPD), including 30 minutes of pharmacotherapeutic content, by listening to the full recording and completing an evaluation at courses.ons.org by July 10, 2027. The planners and faculty for this episode have no relevant financial relationships with ineligible companies to disclose. ONS is accredited as a provider of nursing continuing professional development by the American Nurses Credentialing Center's Commission on Accreditation.

Learning outcome: Learners will report increased knowledge related to drug interactions in oncology care.

Episode Notes

• Complete this evaluation for free NCPD.
• ONS Podcast™ episodes: Pharmacology 101 series
• ONS Voice articles:
• Are Your Patients Taking Herbs That May Interact With Their Cancer Drugs?
• Pharmacogenomics Testing Helps to Ensure That Effective Therapy Is Safe Therapy
• Use of Herbal Products Carries Risk for Drug Interactions, but Patient–Clinician Knowledge, Communication Remain Low
• What the Research Says About Drug Interactions and Medical Cannabis
• ONS books:
• Chemotherapy and Immunotherapy Guidelines and Recommendations for Practice (second edition)
• Clinical Guide to Antineoplastic Therapy: A Chemotherapy Handbook (fourth edition)
• ONS Huddle Cards:
• DPYD Gene and DPD Enzyme
• Pharmacogenomics
• ONS Oral Anticancer Medication Toolkit
• American Journal of Nursing articles:
• Understanding Pharmacokinetics: Part1: Drug Absorption
• Understanding Pharmacokinetics: Part 2: Drug Distribution
• Understanding Pharmacokinetics: Part 3: Drug Metabolism
• Understanding Pharmacokinetics: Part 4: Drug Elimination
• Journal of Nuclear Medicine Technology articles:
• Pharmacology, Part 1: Introduction to Pharmacology and Pharmacodynamics
• Pharmacology, Part 2: Introduction to Pharmacokinetics
• ClinPGx

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Highlights From This Episode

"One of the most notable food interactions that interacts with many different medications is actually grapefruit or grapefruit juice. This is known to be a very strong CYP3A4 inhibitor. … A lot of medications are metabolized through the CYP3A4 pathway. By inhibiting the effect of these enzymes, that can actually increase and significantly increase the concentrations of these therapies. It's not an interaction that's just limited to grapefruit. I would say grapefruit being in the food interaction is kind of one of the most well-known, but it can also be seen with other foods as well, like pomegranate juice or a very specific type of orange called Seville oranges. And this is really just due to the presence of a substance called furanocoumarins." TS 6:12

"There have been a pretty large number of genes identified that are responsible for coding some of those common enzyme families that I had been discussing, some of those CYP450 enzymes, but other enzymes as well that are important for drug metabolism. Based on the type of gene, there could be some different categories where patients are normal metabolizers, intermediate metabolizers, or poor metabolizers. There are some other categories as well based on the type of gene we're looking at. And that can ultimately impact the way you are able to metabolize drugs." TS 15:56

"Another common [geneotypic variation] that we always think about in oncology is G6PD, where if someone has G6PD deficiency, these patients can be at greater risk of hemolytic anemias when receiving certain types of therapies. Dapsone and rasburicase are just a couple that have been associated with this risk." TS 17:50

"One of the big concerns is always polypharmacy. Our patients truly can be on a lot of medications. In the field that I work in, transplant, patients automatically from their transplant are on many, many different medications that can potentially predispose them to side effects. … But I think when it comes to the many drug interactions that may flag in these situations, we really have to look at the patient as a whole. Like, how long have these patients been on these therapies? Are they having side effects? Have they been on the combination for a very long time now? So I think that not just looking at the drug reference and seeing that there are like 10 different interactions flagged, but really assessing your patient as a whole can be very important—just because real-world practice, of course, is not black and white. It's often very gray, so it's just important to use clinical judgment in those scenarios." TS 26:10