What are the dangers of drug interactions with herbal medicines?

Plants have been used in the treatment of many diseases since ancient times, while also having served as a major source of modern single compound drugs. Herbal medicines continue to be widely used globally due to specific health beliefs [1,2] and due to scientific information becoming more and more available on their benefits to patients as well as their safety [3]. It is true that many plants that have been used traditionally for therapeutic and culinary applications are generally safe, but it is also important to know that some plants are highly toxic and can even be deadly [3]. When patients take herbal medicines in conjunction with their prescribed allopathic medicines, interactions may occur between the phytochemicals in the herbalmedicines and active ingredients of prescription drugs through several mechanisms, which can be defined as either pharmacokinetic or pharmacodynamic in nature. These interactions can impact on the pharmacological activity, blood levels, metabolism or toxicity of allopathic drugs [1,2]. Herbdrug interactions are based on the same pharmacological principles as drug-drug interactions [4]. In contrast to single compoundcontaining allopathicmedicinal products, herbalmedicines usually contain a complexmixture of phytochemicals that are producedas secondary metabolites. An herbal medicine (e.g. extract or plant material) can easily contain more than 150 ingredients, which makes identification of the causing factor for adverse effects and interactions difficult [5]. In addition, adverse effects due to herbdrug interactions are in general poorly reported and documented, a problem exacerbated by the lack of disclosure by patients of its use to their healthcare providers [2]. Pharmacokinetic interactions specifically refer to changes (i.e. enhancement or inhibition) in the absorption, distribution, metabolism, and excretion of drugs instigated by the co-administered herbal medicine [1], while pharmacodynamic interactions include synergistic or antagonistic pharmacological effects [6].