Abstract

Background: Some oncological patients tend to have constipation. To relief this symptom, they are induced to take natural products which could be responsible for herb-drug interactions,and giveunexpected therapeutic effects.In this paper we will discuss, as examples, clinical events resulting from the concomitant use ofthese products and chemotherapy.
Methods: The study was performed based on the critical analysis of real clinical cases occurred with the patients followed at the Observatory of Herb-Drug Interactions, head office in Faculty of Pharmacy University of Coimbra (OIPM/FFUC; www.oipm.uc.pt), in collaboration with the Oncology Hospital (Portuguese Institute of Oncology).
Results: From the data collectedthe risk of inefficacy of the treatments could be from the intake of mucilaginous products and anthraquinonederivatives. The first canreduced the absorption of the oral chemotherapy, as Tamoxifen, used inconcomitant intake. In this group the predominance goes to seeds as Chia, Flaxseed, Hollyhock and Plantains andother mucilaginous products as Algae and Mallow. The second group corresponds to herbs with anthraquinonederivativesthatwere many times the first choicedue to its intense laxative activity. These compounds are present in plants as Aloe, Buckthorn and Sene. They can decrease absorption of drugs, especially the ones that have low oral absorptionand, consequently,they can cause an inefficacy of the treatment. Pharmacodynamic interactions can also occur. For example, extracts of Aloe are capable to promote angiogenesis and inhibit irreversibly CYP3A4 increasing plasma concentration of drugs or even decreasing active metabolites from pro-drugs.
Conclusion: Oncological patients are easy targets for marketing such products and may bevictims of dangerous interactions that, at the limit, can result in death. Furthermore, it is important that doctorsare also aware of these questions to help in the identification of problems and avoid failure of treatmentsby inefficacy or increase of toxicity effects. The discussion carried out in this paper will serve as a preliminary alert about the issue that can be used to perform further studies.