Ethical considerations and challenges in herbal drug trials with the focus on scientific validity and risk assessment.

Scientific validity and risk assessment are two main ethical issues which raise specific challenges and are unique to clinical trials investigating crude extracts/fractions from herbal materials. There are considerable challenges for both clinical investigators and ethics committee members in dealing with such issues, many of them remain unresolved, resulting in a large variation in ethical requirements, justification, and decisions. Despite a remarkable surge in herbal medicine research globally, a number of clinical investigators or even ethics committee members have limited confidence in dealing with related ethical issues. In this article, we extensively review and discuss the two main ethical issues (i.e., scientific validity and risk assessment) and highlight key considerations that are important for ethical review and justification for the conduct of herbal drug trials.