Pharmacokinetics and pharmacodynamics in interactions between medicinal herbs and drugs

© 2018 Nova Science Publishers, Inc. There is a regulatory structure for herbals in the European Community. The European Medicines Agency (EMA) and the National Competent Authorities (NCAs) are in charge of registration of herbal medicines. The European Food Safety Authority (EFSA) is dealing with herbal food supplements. Reporting of interactions between herbalmedicines, can be traced within a pharmacovigilance network. Such networking does not exist for food supplements. The quality of reporting is important to enable the investigation of interactions between herbals and drugs. In contrast with conventional drugs, characterization of herbal preparations implies several quality issues, starting with the right plant species and the way the herbal material was processed. Mechanisms of action should be taken into account in order to explain synergism or antagonism based on pharmacokinetics and/or pharmacodynamics. St. John’s wort is a plant species that can interfere with a whole list of medications (see Table 1). Interaction with hormonal contraceptives is an interesting example, as combination with St. John’s wort or Hypericum perforatum herb may lower the effectiveness of the former, and lead to unwanted pregnancy. Interactions caused by other herbals are discussed. Special attention is given to cardiovascular effects, like additional anticoagulant or antiplatelet activity, although predictions are not always easy to make with Ginkgo biloba and hawthorn as examples. Cannabis is presented as a complicated case, with mainly effects on the central nervous system. Attention is focused on the concomitant use of herbals during chemotherapy of cancer. Recommendations are mainly based upon experimental data, as clinical trials are scarce. These data suggest alleviation of toxicity of chemotherapeutic agents, but do not exclude enhanced toxicity. The chapter ends with recommendations for investigating possible interactions of herbals with conventional drugs. Gathering reliable information on causality of interactions, means asking the right questions.

ISBN:9781536135527

Publication year:2018