Pseudohyperaldosteronism and associated hypokalemia are serious adverse effects caused by glycyrrhizinic acid (GA) present in Kampo medicines containing Glycyrrhizae Radix (GR); GA is the major component of GR. To obtain knowledge about the effective and safe use of Kampo medicines, we analyzed the quantities of GA in Kampo medicines by HPLC. The quantities of GA in 13 Kampo decoctions containing GR (2-6 g/day) were found to be almost 2-3.5 fold higher than those of the corresponding Kampo extract products. Among the Kampo extract products containing GR (3 g/day), the GA quantity in Shoseiryuto was significantly lower compared with that in the others, and Pinelliae Tuber as well as Schisandrae Fructus were found to contribute to the decrease in GA quantity. The GA quantity in the Yokukansakachinpihange decoction was found to be lower than that in the Yokukansan decoction; this was caused by the presence of Pinelliae Tuber and Citri Unshiu Pericarpium. Analysis of inter-product variations in GA quantities among the Kampo extract products revealed a maximum 2.6-fold difference in the quantities in the Shoseiryuto extract products from different companies. Our analyses show that GA quantities in Kampo medicines are influenced by the presence of concomitant crude drug constituents. This results in differences in GA quantities between decoctions and extract products having the same Kampo formula, and also among the Kampo extract products from different companies. It is recommended that GA quantities in Kampo extract products should be presented to prevent the adverse effects caused by GA.
