Cancer patients receiving chemotherapy should have all their medications and herbal supplements reviewed by a pharmacist who specialises in cancer therapy, researchers say.
More than half the patients in a recent study reported 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 lead study author Dr Allan Ramos-Esquivel of the University of Costa Rica in San Jose.
“These patients are at high risk of herb-drug interactions and drug-drug interactions,” he told Reuters Health.
Ramos-Esquivel and colleagues 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.
Working with a clinical pharmacist, the researchers identified 36 potential interactions in 26 patients, or 17 percent. The researchers then notified the oncologist who prescribed the anti-cancer drugs, and in all cases, oncologists modified the patients’ therapy.
“The treatment of cancer has shifted in the past decade to the use of more oral agents,” said John Bossaer of East Tennessee State University in Johnson City. Bossaer, who wasn’t involved with this study, has researched drug interactions and anti-cancer drugs.
“Because these newer drugs are taken orally, many patients (and I fear some clinicians) perceive them as safer,” he told Reuters Health by e-mail. “While these oral agents do not generally cause the life-threatening toxicities of IV chemotherapy, they cause many other side effects, which can be worsened by other medications.”
Herbal-drug interactions, in particular, are concerning because of unanswered questions and scientific gaps, Bossaer added. Herb-drug interactions go unnoticed because formal drug interaction studies don’t typically include them.
“Moreover, many patients do not openly disclose their use of herbal medications, either because of fear of judgment from their physician or assuming their use isn’t related to their treatment,” he said.
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 a two times higher risk of a drug interaction, the authors found.
“It is not as black and white as it may seem,” Bossaer said.
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.
“Patients or family members of patients should explicitly ask if a clinical pharmacist has checked their medications for any significant drug interactions,” Bossaer said. “Some may require a medication change, and others may require more frequent lab monitoring.”
