OECD Guideline of Acute Inhalation toxicity

OECD Guideline test as per acute Inhalation toxicity:- 433 , 436

1. OECD Guideline Of Acute Inhalation Toxicity Presented by – Saurav Verma M.Pharm Phamacognosy Roll no – 242389 Semester- 2 nd Submitted to- Dr. Dinesh kumar (Assistant Professor) Head Of Department Pharmaceutical science DEPARTMENT OF PHARMACEUTICAL SCIENCE CENTRAL UNIVERSITY OF HARYANA, MAHENDRAGARH

2. INTRODUCTION Toxicity studies conducted according to OECD guidelines are designed to evaluate the potential hazards of chemicals, substances, and formulations. The Organisation for Economic Co-operation and Development (OECD) provides a series of standardized test guidelines to help ensure the safety of chemicals, chemicals used in products, and pharmaceuticals, as well as to evaluate their potential risks to human health and the environment. These studies are integral for regulatory purposes, safety assessments, and risk evaluations.  

3. Different categories of toxicity studies as per the OECD guidelines: Acute Toxicity Subchronic Toxicity Chronic Toxicity Carcinogenicity Reproductive And Developmental Toxicity Genotoxicity (Mutagenicity) Ecotoxicity (Environmental Toxicity) Skin And Eye Irritation Studies Sensitization Studies Acute And Chronic Aquatic Toxicity

4. Purpose: of OECD Guideline. The purpose of the OECD Guidelines for Multinational Enterprises on Responsible Business Conduct is to encourage positive contributions to economic, environmental, and social progress by multinational enterprises (MNEs), while minimizing any adverse impacts associated with their operations, products, and services.  OECD guidelines aim to ensure the safety of chemicals and chemical products by providing standardized methods for assessing their potential adverse effects on human health and the environment.  Promotes responsible business conduct. Enhance sustainable development etc.

5. Acute inhalation toxicity. Objective- The purpose of this guideline is to assess the toxic effects of a substance following short-term inhalation exposure. This helps determine the lethal concentration (LC50) for inhalation, which is the concentration of a substance that causes death in 50% of the exposed animals. The guideline also provides information on signs of toxicity, organ damage, and other acute health effects.

6. Principle - Aims to assess the acute toxicity of A test substance by inhalation, using A fixed concentration procedure that focuses on evident toxicity (clinical signs) rather than death as the endpoint, reducing the number of animals needed.  It is a principle of the method that only moderately toxic concentrations are used so that 'evident toxicity', rather than death/moribundity is used as an endpoint, and concentrations that are expected to be lethal are avoided.

7. OECD Test Guideline : Acute Inhalation Toxicity: 433 & 436 OECD Test Guidelines 433 (Fixed Concentration Procedure) and 436 (Acute Toxic Class Method) are used for assessing acute inhalation toxicity, with  433 focusing on "evident toxicity" rather than death as an endpoint and 436 using a stepwise procedure to determine toxicity classification.

8. OECD GUIDELINE- • Acute toxicity study for inhalation was documented as document no. 39 as OECD GUIDELINE FOR THE TESTING OF CHEMICALS Acute Inhalation Toxicity. • Guideline 436 (2009) • Guideline 433 (2017) • The original acute inhalation Test Guideline 403 was adopted in 1981.

9. Initial Consideration In accordance with this Test Guideline all available information on the test article, including existing studies (e.g. TG 436) whose data would support not doing additional testing should be considered by the testing laboratory in order to minimize animal usage. Information that may assist in the selection of the most appropriate. 1. species 2. strain 3. sex 4. mode of exposure

10. PRINCIPLE OF THE TEST • This revised TG 403 has been designed to obtain sufficient information on the acute toxicity of a test article to enable its classification and to provide lethality data (e.g. LC50, LC01 and slope) for one or both sexes as needed for quantitative risk assessments.

11. This Guideline offers two test methods. The first method is a Traditional protocol in which groups of animals are exposed to a limit concentration (limit test) or a series of concentrations in a stepwise procedure for a predetermined duration of usually 4 hours. Other durations of exposure may apply to serve specific regulatory purposes. The second method is a (C x t) protocol in which groups of animals are exposed to one (limit concentration) or a series of multiple concentrations over multiple durations.

12. DESCRIPTION OF THE METHOD Selection of animal species Housing and feeding conditions Preparation of animals Mode of exposure Head/nose-only exposure technique Whole-body exposure technique Exposure conditions Particle size Generation of test atmospheres Chamber airflow Chamber temperature Relative humidity Concentration of test chemical Particle size distribution Nominal concentration

13. 1. Selection of animal species:- Healthy young adult animals of commonly used laboratory strains should be used. • The preferred species is the rat and justification should be provided if other species are used. 2. Preparation of animals 1. Females should be nulliparous and nonpregnant. 2. On the exposure day, animals should be young adults 8 to 12 weeks of age, and body weights should be within ±20% of the mean weight for each sex of any previously exposed animals of the same age. 3. Animal husbandry The temperature of the experimental animal maintenance room should be 22±3°C. The relative humidity should ideally be maintained in the range of 30 to 70%, though this may not be possible when using water as a vehicle. Before and after exposures, animals generally should be caged in groups by sex and concentration, but the number of animals per cage should not interfere with clear observation of each animal and should minimize losses due to cannibalism and fighting.

14. EXPOSURE CONDITIONS:- 1. Administration of concentrations 2. Particle-size distribution 3. Test article preparation in a vehicle 4. Control animals

15. MONITORING OF EXPOSURE CONDITIONS- 1. Chamber airflow 2. Chamber temperature and relative humidity 3. Test article: Nominal concentration 4. Test article: Actual concentration 5. Test article: Particle size distribution

16. PROCEDURE- • Two study types are described below: 1. the Traditional protocol 2. and the C x t protocol Both protocols may include a sighting study, a main study, and/or a limit test or testing at limit concentration.

17. Main study - Exposure Session I-Testing at the limit concentration • 1 animal/sex per concentration/time point; 10 animals in total a • Target concentration = limit concentration. • Expose five groups of animals at this target concentration for durations of 15, 30, 60, 120 and 240 minutes, respectively. Exposure Session II - Main Study • 1 animal/sex per concentration/time point; 10 animals in total. • Expose five groups of animals at a lower concentration d (1/2L) with slightly lower duration of exposure.

18. Exposure Session III - Main Study • 1 animal/sex per concentration/time point; 10 animals total. • Expose five groups of animals at a lower concentration d (1/4L) with slight longer exposure durations. Exposure Session IV' - Main Study • 1 animal/sex per concentration/time point; 10 animals total. • Expose five groups of animals at a lower concentration d (1/8L) with slightly longer exposure durations Exposure Session IV - Main Study • 1 animal/sex per concentration/time point; 10 animals total. • Expose five groups of animals at a higher concentration e (2L) with slightly shorter exposure durations

19. Results- Tabulation of chamber temperature, humidity, and airflow; - Tabulation of chamber nominal and actual concentration data Tabulation of particle size data including analytical sample collection data, particle size distribution. Individual body weights of animals collected on study; date and time of death if prior to scheduled euthanasia, time course of onset of signs of toxicity and whether these were reversible for each animal Necropsy findings and histopathological findings for each animal, if available Lethality estimates (e.g. LC50, LD01) including 95% confidence limits, and slope (if provided by the evaluation method) Statistical relation, including estimate for the exponent n ( C x t protocol). The name of the statistical software used should be provided.

20. Reference - OECD GULIDELINE . OECD Test Guidelines [cited 2022 9 December]. Availablefrom : https://www.oecd.org/chemicalsafety/testing/oecdguidelinesforthetestingofchemicals.htm OECD guidelines for testing of chemicals number 423 ( acuteoral toxicity- acute toxic class method) 2001. p.1-5 [cited2022 16 December]. Available from: https://www.oecd-ilibrary.org/environment/test-no-423-acute-oral-toxicity-acute-toxic-class-method_9789264071001-e (PDF) OECD GUIDELINES FOR ACUTE ORAL TOXICITY STUDIES: AN OVERVIEW . Available from: https://www.researchgate.net/publication/373895537_OECD_GUIDELINES_FOR_ACUTE_ORAL_TOXICITY_STUDIES_AN_OVERVIEW [accessed Apr 05 2025]. OECD guidelines for testing of chemicals number 423 ( acuteoral toxicity- acute toxic class method) 2001. p.8. [cited 202216 December]. Available from: https://www.oecd-ilibrary.org/environment/test-no-423-acute-oral-toxicity-acute-toxic-class-method_9789264071001-en (PDF) OECD GUIDELINES FOR ACUTE ORAL TOXICITY STUDIES: AN OVERVIEW . Available from: https://www.researchgate.net/publication/373895537_OECD_GUIDELINES_FOR_ACUTE_ORAL_TOXICITY_STUDIES_AN_OVERVIEW [accessed Apr 05 2025].