Challenge tests and kampo medicines: case report and review of the literature

In order to diagnose Kampo medicine-induced liver injury, a challenge test using the suspected medicine is the most reliable method of assessing the relationship between Kampo medication and liver injury. However, such a challenge test may cause severe liver injury. We examined the clinical features and safety of challenge tests conducted by a physician in a case of Kampo medicine-induced liver injury that we encountered as well as in the previous literature (six cases) in Japan. In all cases except two, one-third of the daily dose was given a few times for the challenge test (challenge dose was not described in two cases). The reaction induced by the challenge peaked 1-3 days after challenge. Mild eosinophilia (6%) was observed in two cases. All liver injuries induced by challenge cleared within 2 weeks, and neither severe nor fatal liver injury was observed. In conclusion, a challenge with a small dose of Kampo medicine conducted in our case and in the previous literature induced mild and reversible liver injury. The safety and availability of challenge with a small dose of Kampo medicine should be further examined in a larger population with Kampo medicine-induced liver injury.