NATURAL PRODUCT–DRUG INTERACTIONS IN ONCOLOGY: CHEMICAL BASIS, PHARMACEUTICAL CONSIDERATIONS, AND CLINICAL IMPLICATIONS

Abstract

Cancer patients frequently use natural products to help them with their illness in addition to their oncology treatment. Patients often choose to use complementary and alternative therapies to try to improve their overall quality of life and reduce adverse effects from their chemotherapy treatments. In many cases, patients are using herbal/multiple supplements or other phytochemicals at the same time as chemotherapeutic agents or targeted therapies. Unfortunately, this can lead to significant herb-drug interactions that can alter the patients' therapeutic outcome. These may occur via pharmacokinetic mechanisms (e.g., inhibition or induction of cytochrome P450 enzymes, transporters, or metabolism) and pharmacodynamic mechanisms (e.g., modifying the effectiveness or toxicity of the drug). The most common natural products that have been shown to have a potential effect on the absorption, distribution, metabolism, or elimination of chemotherapeutic agents and targeted therapies include St. John's Wort, turmeric, green tea, ginseng, garlic, and grapefruit. Knowledge of the chemical compounds responsible for these interactions is necessary to promote optimal pharmaceutical care and limit the negative clinical consequences. This review will identify the chemical basis for natural product-drug interactions in the oncology population and note key pharmaceutical considerations of formulation and metabolism, as well as evaluate the clinical implications based on the current literature. Keywords: Natural products; Herb–drug interactions; Oncology; Chemotherapy; Phytochemicals; Cytochrome P450; Drug transporters; Pharmacokinetics; Pharmacodynamics; Cancer therapy; Dietary supplements; Clinical implications