Progress in the design and quality control of placeboes for clinical trials of traditional Chinese medicine

In recent years, new preparations of traditional Chinese medicines (TCMs) have been developed, increasing the need for their clinical trials. Using placeboes rather than control drugs is increasingly popular in clinical trials of TCMs, as the therapeutic effects of the tested TCMs can be more properly judged. The basic attributes of TCM placeboes include similarity, safety, applicability and controllability. In particular, it is necessary to have similarities in appearance, color, smell and taste between the tested TCMs and placeboes. This is quite difficult for some TCMs due to their distinctive smell and taste. On the other hand, according to the TCM theory on homology of medicine and food, many foods also have certain bioactivities, potentially further complicating the selection of materials for TCM placeboes. In this review, firstly, studies on the special smell and taste of TCMs were introduced. Then, the preparation quality evaluation processes for TCM placeboes were summarized and discussed, based on the relevant literature published in recent years and the research results from our own lab. This review will facilitate the further research and development of TCM placeboes.