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Potential Drug-Drug and Herb-Drug Interactions in Patients With Cancer

Q HEALTH – Cancer patients receiving chemotherapy should have all their medications and herbal supplements reviewed by a pharmacist who specializes in cancer therapy, revealed a study led by Dr. Allan Ramos-Esquivel of the University of Costa Rica in San Jose.

The study reported that more than half the patients taking prescription medications, over-the-counter drugs or herbal supplements along with chemotherapy, and roughly one in six patients were using products that put them at risk for potentially harmful drug interactions.

“Patients with cancer frequently use herbal supplements and other medications,” said Dr. Ramos-Esquivel. Adding, “these patients are at high risk of herb-drug interactions and drug-drug interactions.”

The researchers surveyed 149 newly diagnosed cancer patients about prescription or over-the-counter drugs and herbal supplements they were taking as they started on new anti-cancer therapies, and identified 36 potential interactions in 26 patients, or 17%. The researchers then notified the oncologist who prescribed the anti-cancer drugs, and in all cases, oncologists modified the patients’ therapy.

The Journal of Oncology Practice, reported the methods used by the researchers was to ask patients starting a new anticancer therapy to complete a questionnaire to identify the concomitant use of any over-the-counter drug or herbal supplement. Potential DDIs and HDIs were identified using two different databases.

In this study, 84 patients, or 56% were using herbal supplements at the time of their first cancer drug prescription.

Using two or more medicinal products in addition to the anti-cancer therapy was associated with two times higher risk of a drug interaction, the researchers found.

“It is not as black and white as it may seem,” said John Bossaer of East Tennessee State University in Johnson City.

For example, he explained, the prostate cancer drug enzalutamide decreases the effectiveness of several medications, including ticagrelor, which is often used after stent placement for heart disease. A drug interaction may put the patient at greater risk for a heart attack, which isn’t typically noticed until the heart attack happens.

“This nuance requires both extensive drug and clinical disease-state knowledge,” Bossaer said. “This is exactly what clinical pharmacists are trained to do.”

A limitation of the study is that it relies on the self-reporting nature of the questionnaire. Future research should better identify drug and herbal interactions with chemotherapy, the study authors wrote in the Journal of Oncology Practice.