Estimation of residual rate and apparent half-life time of drugs using the method of acute mortality of animals

The ip LD50 of mice was determined from “log dose-death probit” straight line. The mice were divided into 5-6 groups, 20 or 40 mice in each group. The same doses( which should be in the range of LD5-LD35) were injected at intervals varied from 0.5 to 72 h. The mortality o each group after 2 dosages was obtained and its corresponding dose was found from the above-mentioned straight line. The residual % after the first dosage=( Corresponding dose of that mortality-Given dose)/(Given dose) *100%. On the basis of “interval time-residual % relationship”, a curve of dynamic change in residual % after initial dosage was drawn, taking residual % in log to make the diagram a straight line during elimination phase. This line resembled that obtained by the method of blood drug concentration. By this method, the t1/2 of quinidine sulfate, caffeine, sulfadiazine sodium, and the pesticide Beauveria bassiana were estimated to be 4.1,2.5,19, and 29 h,respectively.