OECD GUIDE LINE 423Acute Oral Toxicity-Acute Toxic Class Method Guided By Presented by Dr. Najeeb Jahan Shamim Ahmed Ilmul Advia Kamal Ahmad NIUM, Bangalore-91
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.
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.
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.
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.
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.
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.
CONTD…. GHS of classification improve the knowledge of hazardous chemical and move towards the elimination of it mainly which are carcinogenic in nature.
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.
OECD WAY OF WORKING Data collection Analysis Discussion Decision Implementation Peer review
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.
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.
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.
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.
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.
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.
PREPARATION OF ANIMALS Animals are randomly selected and marked it. Kept animal in their cage at least five days prior to dosing.
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.
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.
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.
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.
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.
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.
BODY WEIGHT Individual weight of animal should be determined shortly prior to test substance is administered and at least weekly thereafter.
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.
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.
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