LD 50 determination of Procaine. Purpose Study the method, procedure and calculation of LD 50 determination. Principle
LD50 determination of Procaine
Study the method, procedure and calculation of LD50 determination.
The lethal dose is usually used to evaluate the degree of acute toxicity of the drug. Half lethal dose is one of the indicators because it is the highest sensitivity point on the dose – reaction curve. Long tail “s” like curve (figure 1) is drawn by using death rate as the ordinate and the dose as the abscissa for certain relation between dose and biological reaction.
it is because the number of the animals selected randomly which have high sensitivity or have no sensitivity is completely small, while the sensitivity of majority animals are close to each other while.
The relationship between death and dose
There are a maximum slope in 50% death rate and two mind ends which the right is longer than the left.
Figure 2 The relationship between death rate and logarithm dose
The curve figure 1 is transformed to the following curve (figure 2) with features of the symmetry of the left and right and the point of symmetry in 50% death rate by using logarithm transformed dose as abscissa. At the point, the slope is maximum and the change is obvious. That is to say that the reaction of the animal to the drug dose is most sensitive, and dose is the most accurate and error is minimus.
5 4 3 2 1
0.1 0.2 0.3 0.4 0.5 lgD
Probit, a kind of function in mathematics, is the transform of the death rate, and it has a line relation with the logarithm dose (figure 3).
The transformation is called probit method and LD50 can be calculated by diagram or formula.
Figure 3 The relation between probit and logarithm dose
1.Separate the male from the female, and weigh them respectively. Put the mice of the same weight class(eg,18.0~18.9g)into the same mouse cage.
2.Mark the same signal on all the mice in the same cage.
3.Randomly,divide the mice into 5 groups of 10 mice each with similar sex and weight in the turns of the weight class(from big to small or in inverse).
Number of group 1# 2# 3# 4# 5#
Number of mice 1 2 3 4 5
5 1 2 3 4
4 5 1 2 3
3 4 5 1 2
2 3 4 5 1
4.Inject intraperitoneally 1% procaine to the mice in each group with the dose of 130mg/kg, 153mg/kg,180mg/kg,212mg/kg and 249mg/kg respectively using 1:0.85 as the ratio between adjacent groups . Number the dead in each group within 30 min.
5.Calculate LD50 and 95% confidence limit by improved Kou” method and Bliss method.
Experiment report should cover : 1) the batch number, specification, manufacturer, physical and chemical properties, concentration of the drug and the temperature in the laboratory. 2) the species, sex, weight range, groups, route of administration, toxic symptom, death time and death rate of the animal. 3) the result should be calculated by SPSS (edition higher than 10.0).