Yokukansan is a Kampo formula that is commonly used by the elderly because it is expected to improve peripheral symptoms of dementia and delirium. However, side effects from its use are frequently reported in the elderly. In particular, pseudoaldosteronism caused by the licorice contained in yokukansan leads to hypertension, hypokalemia, and muscle weakness, which may result in death. This study aimed to identify the risk factors of pseudoaldosteronism with yokukansan use. Using cases reported in the Japanese Adverse Drug Report (JADER) database, the reporting odds ratio (ROR) was calculated and compared to assess the risk of pseudoaldosteronism for each licorice-containing Kampo formula. We also analyzed the risk factors for pseudoaldosteronism in patients taking yokukansan. Yokukansan (ROR 2.4, 95% confidence interval (CI) 1.9-2.8; p < 0.001) had a higher risk of pseudoaldosteronism than that of other licorice-containing Kampo formulas. Furthermore, the results of a logistic regression analysis in patients taking yokukansan showed that the licorice dose (OR 1.5, 95% CI 1.2-2.0; p < 0.01), older age (<70 years, OR 5.9, 95% CI 1.8-20; p < 0.01), dementia (OR 2.8, 95% CI 1.6-4.9; p < 0.001), low body weight (<50 kg, OR 2.2, 95% CI 1.1-3.5; p 0.034) were risk factors for pseudoaldosteronism, Although not significant, treatment with loop diuretics (OR 1.8, 95% CI 0.98-3.5; p 0.059) tended to increase the risk of pseudoaldosteronism. In summary, patients must understand the risk factors when considering taking yokukansan and reduce the licorice dose they consume.

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Individual differences in gut microbiota can affect the pharmacokinetics of drugs. Yokukansan is a traditional Japanese kampo medicine used to treat peripheral symptoms of dementia and delirium. A study examining the pharmacokinetics of the components of yokukansan reported large individual differences in the pharmacokinetics of glycyrrhizic acid (GL). It is known that GL is metabolized by intestinal bacteria to glycyrrhetinic acid (GA), which is absorbed in the gastrointestinal tract. Thus, the gut microbiota may affect GL pharmacokinetics. We aimed to clarify the relationship between the gut microbiota composition and pharmacokinetics of GL in yokukansan. Mice were orally administered yokukansan, following the administration of various antibiotics, and the plasma concentration of GA and composition of gut microbiota were measured. The GA plasma concentration was low in mice treated with amoxicillin and vancomycin. The composition of gut microbiota revealed a different pattern from that of the control group. Mice with low plasma levels of GA had lower levels of the phylum Bacteroides and Firmicutes. Additionally, bacteria, such as those belonging to the genera Parabaceroides, Bacteroides, Ruminococcus and an unknown genus in families Lachnospiraceae and Ruminococcaceae, exerted positive correlations between the gene copies and plasma GA levels. These bacteria may contribute to the absorption of GA in the gastrointestinal tract, and multiple bacteria may be involved in GL pharmacokinetics. The pharmacokinetics of GL may be predicted by evaluating the composition of gut bacteria, rather than by evaluating the amount of a single bacterium.