The document discusses OECD Guideline 423 for acute oral toxicity testing. It outlines that the guideline uses a stepwise testing process with only 3 animals per step to classify chemicals according to their toxicity while minimizing animal use. The testing involves observing animals for signs of toxicity after administering chemical doses and determining subsequent dose levels based on mortality responses. The goal is to classify chemicals according to the globally harmonized system to improve knowledge of hazardous chemicals.

1. OECD GUIDE LINE 423
Acute Oral Toxicity-Acute Toxic Class Method
Guided By Presented by
Dr. Najeeb Jahan Shamim Ahmed
Ilmul Advia Kamal Ahmad
NIUM, Bangalore-91

2. INTRODUCTION
 Organization for the economic co-
operation and development.
 Established in 1961.
 This test guide line encompasses different
area of development like
education, health, finance, market, industr
y and chemicals etc.
 Headquarter is in Paris (France).
 Membership-34 countries.
 Secretary general is Angel Gurria.

3. CONTD….
 For oral acute toxicity study we follow the
precise LD50 rule.
 The concept of LD50 was given by Trevan in
1927.
 In LD 50 we consider that a single dose of
substances that can be expected to kill the 50%
of animals in a test group.
 This test have gained a general acceptance for
comparing and classifying the toxicity of
chemicals.

4. CONTD…
 Itbecomes a routine test framework for
the oral acute toxicity study
 This study required up to 100 animals for
each chemical (substance) test.
 OECD test guidelines adopted this test as
401 for oral acute toxicity, but animal
welfare organization objected to this test
and request to use minimum number of
test animals.

5. CONTD….
 Forum of OECD test guide line made a
meeting and after a periodical review in the
light of scientific progress developed an
alternative method for oral acute toxicity. In
this method the number of tested animals
reduced up to one third.
 Adopted OECD test guideline 401 was deleted
in 2002. Now we adopt the OECD test guide
line 423 for acute oral toxicity.

6. CONTD…
 This toxicity study is based on acute toxic
class method (ATC).
 ATC method is a sequential testing procedure
using only 3 animals of one sex per step at any
of the defined dose level.
 Depending upon the mortality or moribund
status of the animals on average 2-4 steps may
be necessary to allow the judgment on the
acute oral toxicity of test substances.

7. CONTD……
 Globally Harmonized System (GHS) for the
classification of a chemical: Before this
system for a single hazard substance, there are
different standard in different country so that it
is very difficult to prevent the toxicity of the
substances.
 GHS of classification of substance came in
existence in 1992. according to this system a
toxic substance have same labeling all over the
world.

8. CONTD….
 GHS of classification improve the knowledge
of hazardous chemical and move towards the
elimination of it mainly which are carcinogenic
in nature.

9. MISSION
 Mission of the organization for economic
co-operation and development is to
promote policies that will improve the
economic and social well being of people
around the world.
 OECD guideline set an international
standard on a wide range of thing, one of
them is safety of chemicals.
 OECD council make decision, and
government implement it.

10. OECD WAY OF WORKING
Data collection
Analysis
Discussion
Decision
Implementation
Peer review

11. INITIAL CONSIDERATION
 Test substances, at dose that are known to be
causes marked pain and distress due to
corrosive or severely irritant actions, need not
to be administered.
 Moribund animals or animals obviously in pain
or showing sign of severe distress shall be
humanely killed.

12. CONTD…
 But these animals are considered in the
interpretation of the test result in the same
way as animal that died on test.
 According to OECD guide line calculation
of precise dose of LD50 is not necessary
but allow the determination of defined
exposure ranges where lethality is
expected.

13. CONTD…
 All information about the test substances
should be available in laboratory prior
conducting the study.
 This information is necessary to satisfy all
concerned that the test is relevant for the
protection of human health and help in
selection of most appropriate starting dose.

14. PRINCIPLE OF THE TEST
 Itis based on the stepwise procedure and
use the minimum number of animal per
step.
 Substance is administered orally to a
group of experimental animal at one of the
defined dose.
 Absence or presence of mortality of the
animals at one step determined next step.

15. DESCRIPTION OF THE METHOD
 Selection of animal species: the preferred
rodent species rat, although other rodent
may be used.
 Normally Healthy young adult nullipara
non-pregnant females are used
 Each animal at the commencement of its
dosing should be between 8-12 weeks.

16. HOUSING AND FEEDING CONDITION
 Temperature in the experimental animal
should be 220C ( 30C).
 Relative humidity at least 30% preferably
not exceed 70%.
 Lighting should be artificial.
 For feeding conventional laboratory diet
should be given.

17. PREPARATION OF ANIMALS
 Animals are randomly selected and
marked it.
 Kept animal in their cage at least five days
prior to dosing.

18. PREPARATION OF DOSE
 In general test substance should be administered
in a constant volume over a range of dose.
 Maximum dose for administration should not be
exceeded.
 In rodent dose should not normally exceed 1
ml/100gm of body wt. but in case of aqueous
solution 2 ml/100 gm body wt. can be
considered.
 Dose must be prepared shortly prior to
administration.

19. PROCEDURE
 Administration of dose:
 Test substance administered in a single
dose by gauge using a stomach tube or
suitable intubation cannula.
 In unusual condition when a single dose
is not possible the dose may be given in
fraction over a period but not exceeding
24 hours.

20. CONTD..
 Animal should be fasted prior to dosing.
 After the period of fasting, animal
should be weighed and then test
substance should be administered.
 After administration of test substance
food may be withheld for a further 3-4
hours in rats and 1-2 hours in mice.

21. NO. OF ANIMAL AND DOSE LEVEL
 3 Animals are used for each step.
 The dose level which are used as starting
dose is selected from one of four fixed
dose 5, 50, 300 and 2000 mg per kg body
wt.
 If there is no information about the
substances which are to be tested then for
animal welfare reason it is recommended
to use the starting dose of 300 mg/kg body
wt.

22. OBSERVATION
 After dosing animals are observed very
keenly for first 30 minutes and special
attention given during first four
hours, periodically for 24 hours.
 However the duration of observation
should not be fixed rigidly.
 It should be determined by toxic reaction
and length of recovery period.

23. CONTD…
 The time at which sign of toxicity appear
and disappear are important.
 All the observation record systemically
like changes in
skin, fur, eyes, respiratory, circulatory, AN
S, somatomotor activity and behavioral
pattern.
 Also observe
tremor, convulsion, diarrhoea, salivation, l
ethargy, sleep and coma.

24. BODY WEIGHT
 Individual weight of animal should be
determined shortly prior to test substance
is administered and at least weekly
thereafter.

25. PATHOLOGY
 All the tested animal should be subjected
to gross necropsy.
 All the gross pathological changes should
be record for each animals because it yield
useful information.

26. DATA AND REPORTING
 Individual animal data should be provided.
 All data should be summarized in tabular
form.
 No. of animal displaying the toxicity.
 No. of animal found dead during test.
 Time of death of individual animal.
 Necropsy finding.

27. CONCLUSION
OECD GUIDE LINE 423
 Economic
 Less number of animals are used
 The chemicals also classify according to their
toxicity
 It improve the economic and social well being of
people around the world by providing the safety
documentation of chemicals, which are to be
used as medicine