LD50 determination of
Procaine
Purpose
Study the method, procedure and
calculation of LD50 determination.
Principle
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.
Death rate
There are a
maximum slope
in 50% death
rate and two
mind ends
which the right
is longer than
the left.
Dose
Figure 1
The relationship between
death and dose
Death rate
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.
LgLD50
Figure 2 The relationship
between
death rate and
logarithm dose
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.
5
4
3
2
Death rate
1
0.1 0.2 0.3 0.4 0.5 lgD
Logarithm dose
Figure 3
The relation between probit and logarithm dose
Methods
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.
18g
19g
20g
21g
22g
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.
Results
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).