OBJECTIVE: To investigate the sedative and hypnotic activity of paeoniflorin and freeze-dried Sini San powder on mice and provide a reliable method for determining the pharmacodynamic material basis of Sini San.METHODS: Male adult mice weighing 20-22 g were used in this study. Three experiments were carried out. Synergism with pentobarbital was used as an index for hypnotic effect. Loss of the righting reflex was used to determine the start of sleep.Sleep latency and sleeping time were recorded in each experiment.RESULTS: The coefficient of variation of the suprathreshold dose(55 mg/kg) was significantly lower than that of the threshold dose. The sleep latency of mice was significantly decreased, and the sleeping time of mice was significantly prolonged. The effects of paeoniflorin and Sini San on prolonging the sleeping time of mice induced by pentobarbital sodium were significantly stronger than those in the control group.CONCLUSION: Paeoniflorin produces significant sedative and hypnotic effects, and there is an obvious dose-effect relationship.