Abstract: Objective To compare the acute toxicity of Xuezhining and its separated prescriptions in mice and to explore the mechanism of prescription compatibility, so as to provide a foundation for safe and rational drug use in clinic. Methods Xuezhining was divided into seven combinations by referring to the combination of prescription, single flavor and the characteristics of lipid lowering effect, namely Cassiae Semen and Crataegi Fructus (group 1), Cassiae Semen and Nelumbinis Folium (group 2), Cassiae Semen and Polygoni Multiflori Radix Praeparata (group 3), Polygoni Multiflori Radix Praeparata and Nelumbinis Folium (group 4), Cassiae Semen and Crataegi Fructus and Nelumbinis Folium (group 5), Cassiae Semen and Crataegi Fructus and Polygoni Multiflori Radix Praeparata (group 6), Cassiae Semen and Crataegi Fructus and Polygoni Multiflori Radix Praeparata and Nelumbinis Folium (group 7). The classical method of acute toxicity was used to compare the difference of acute toxicity among Xuezhining and its separated prescriptions. Results The maximum dosage (MFD) of all components of seven groups were respectively 39.60, 34.80, 42.00, 21.60, 37.20, 38.40 and 39.60 g·kg-1, which were respectively equal to 19.05, 14.87, 16.15, 11.87, 12.49, 12.31 and 10.15 times of the clinical daily dosage in 70 kg humans. The MFD of water extracted components of all groups referred were respectively 192.00, 320.40, 192.00, 300.00, 218.40, 177.60 and 192.00 g·kg-1, which were respectively equal to 92.31, 136.92, 73.85, 164.84, 73.36, 56.92 and 49.23 times of the clinical daily dosage in 70 kg humans. The sequence of acute toxicity of all-components of all groups is group 4>group 2>group 5>group 6>group 1≈group 7>group 3; The sequence of acute toxicity of water extracted components of all groups is group 6>group 1≈group 3≈group 7>group 5>group 4>group 2. The main acute toxicity symptoms and signs are poor spirit, negligent action and prostrate. Conclusion The results of the acute toxicity of combinations mentioned above were less than Cassia Semen and Polygoni Multiflori Radix Praeparata which were previously reported in laboratory. It is suggested that the separated prescriptions of Xuezhining which divided according to the prescription structure of traditional Chinese medicine can reduce the degree of acute toxicity of Cassiae Semen and Polygoni Multiflori Radix Praeparata. It also proved that the compatibility of traditional Chinese medicine in safety control is scientific and reasonable. The mechanism of detoxification should be further researched.

Key words: Xuezhining, Cassiae Semen, Polygoni Multiflori Radix Praeparata, compatibility, acute toxicity