by Eric Brand

This is the Xi Xin that should be in all of our clinics. Many Chinese materia medica scholars believe that only the roots of Xi Xin were used in Shang Han Lun times. In fact, the name Xi Xin means "thin acrid," which is thought to be a reference to the thin shape of the roots and their strong acrid taste. Over the centuries, the entire plant became commonly used as Xi Xin, and the whole plant is still widely seen in TCM pharmacies in China and abroad. However, the aerial portions of the plant have significant amounts of aristolochic acid (AA) and are associated with a high incidence of adverse events. The root is largely lacking in AA and is thus considered the safe product for internal use.

In the official pharmacopoeias of Hong Kong, mainland China, and Taiwan, only the root is now listed as the correct item for Xi Xin. If we look at older editions of the PRC Pharmacopoeia, we can see that the whole herb is listed in the 1995 edition, but in the 2005 edition only the root and rhizome are listed. This reflects the discovery of the harmful effects of AA and the trend to eliminate the clinical use of the aerial portion of the plant. Of course, it takes time for the message to get out, so it is not uncommon to still see the whole herb used in both China and the West.

At present, few practitioners understand the issues involved with Xi Xin. It is essential for us all to understand that the root is the product that should be used, not the whole herb.