ABSTRACTAimFor the purpose of reducing both the consumption of crude drug resources and patient burden in preparing the decoctions, we developed a new preparation method for the decoctions of Kampo formula: immersion of powdered crude drugs in hot water (IPCD method), inspired by a method of decoction that was widely used in the Song period of China.MethodsEphedra herb (terrestrial stem of Ephedra sinica), scutellaria root (root of Scutellaria baicalensis), and Kampo formulas that contain several crude drugs including ephedra herb and scutellaria root were powdered, and then immersed in hot water to extract the ingredients. The residue was filtered out using a commercially available tea server. The contents of marker compounds in the decoctions were measured.ResultsUsing the IPCD method, the amounts of marker compounds from ephedra herb and scutellaria root transferred to hot water exceeded by 1.3–1.4‐fold that obtained by the standard method of decocting the same amounts of cut crude drugs for >30 min. The amount of transferred marker compounds reached a plateau within 4 min after the beginning of immersion, suggesting that only 4 min of immersion is sufficient for the IPCD method. The sludge residue of powdered crude drug produced by immersion could be easily filtered with a commercially available tea server.ConclusionUsing this method, the same or greater amounts of marker compounds were transferred in the decoctions in a much shorter time with lower consumption of crude drugs than with the usual decoction method.