Abstract: Objective To study the acute toxicity reaction and to determine median lethal dose and its 99% confidence limit when mice received injection slightly alkaline embelin and ammonia solution from tail vein. Methods Mice received tail vein injection of slightly alkaline embelin and ammonia solution, pilot test was carried out to look for maximum 0% lethal dose and minimum 100% lethal dose. And then, twelve groups mice were injected slightly alkaline embelin and ammonia solution at 0.01 mL·g-1 from tail vein according to 1:0.8 geometric dilution, dose of each group was between minimum 0% lethal dose and maximum 100% lethal dose. Mice poisoning death in each group within 7 days after the treatment was observed. Dead mice were dissected to check primary organs. Median lethal dose and its 99% confidence limit were calculated. Results Mice mortality of the lowest dose group and the highest dose group was between 30% and 70%. There was approximate linear relationship between dosage logarithm and death probability unit, when tail vein injection dose was between 60 mg·kg^-1 and 448 mg·kg^-1. Median lethal dose and its 99% confidence limit were calculated by synthetic analyzing method. Conclusion With equivalent of embelin, mice received tail vein injection of slightly alkaline embelin and ammonia solution, median lethal dose was 153.525 mg·kg^-1 and its 99% confidence limit was 153.525±40.815 mg·kg^-1.

Key words: embelin, slightly alkaline dmbelin and ammonia solution, mice, acute toxicity, median lethal dose