Evaluating the safety of herbal medicines : integrated toxicological approaches

Many complex herbal mixtures are already commonly used worldwide, either for primary health care or as complementary or alternative medicines. Ancient traditional remedies—notably traditional Chinese medicine (TCM) and Ayurveda—have been passed down and refined over their long history of clinical use. Often perceived as innocuous, some herbs exhibit delayed or cumulative toxicity that may not be obviously attributed to the herbs, but instead identified by serendipity or unfortunate clinical findings. Given the large number of herbal products on the market and the relatively low budgets available for research to date, safety assessment in accordance with modern guidelines has been carried out on relatively few herbs. Despite these concerns, a recent survey of practitioners in Europe and China, although limited in scope, provides some reassurance that the vast majority of herbs in regular use are known to be relatively safe. Herbal safety is compromised when any element of the herbal medicine-practitioner-patient triangle is flawed. To meet the challenge, integrating emerging systems-based technologies with conventional means is essential. There remains a clear and urgent need for novel methods able to rapidly pinpoint indicators of major mid-term and long-term toxicities, to yield warning signals, and identify those herbal drugs and formulae that need further toxicological investigation. Recent advances in 'omics and bioinformatics techniques have made it possible to investigate efficacy and toxicity at the organism level and in an individual manner. When further developed and validated, these methods should enhance the detection of insidious toxicities, provide the necessary background information for effective pharmacovigilance, and aid mechanistic studies of specific herbal medicines.