Single dose and repeated dose toxicity studies.pptx

SINGLE DOSE AND REPEATED DOSE TOXICITY STUDIES: FACTORS AFFECTING SUCH STUDIES AS SPECIES,SEX, ROUTE AND DOSE LEVEL

1. A Presentation on Single dose and repeated dose toxicity studies: Factors influencing such studies as species, sex, route, and dose level By – Ayansh Singh M.S.(Pharm.) Regulatory Toxicology

2. Objectives of Non-Clinical studies

3. Introduction Single-Dose Acute Toxicity Testing A single-dose study involves administering a test substance to animals at various dosage levels only once. This helps researchers understand the initial impact of the substance and its potential for acute toxicity. Observations are made over a specific period, often 14 days, to assess mortality, morphological changes, and biochemical alterations in the animals. Repeated-Dose Toxicity Studies Repeated-dose studies delve deeper, investigating the effects of administering the substance to animals at different doses over a defined period, ranging from weeks to months, or even longer for chronic studies. This allows researchers to assess the potential for sub-acute and long-term adverse effects that may not be evident in a single-dose study.

4. Single Dose Toxicity Animals are usually administered with a single dose of the test compound or on rare occasion, in the form of multiple smaller doses given over a period of 24 hours. All animals are monitored for mortality, clinical signs, body weights, and food consumption for14 days. Blood and urine samples may be collected on Day 15 from all surviving animals and subjected to clinical pathology analysis (i.e., hematology, coagulation, clinical chemistry, and urinalysis). Upon completion of the 14-day observation period, all surviving animals are euthanized and subjected to a complete necropsy.

5. Repeated Dose Toxicity The objective of repeat-dose toxicity studies is to evaluate adverse effects of compounds when administered to the experimental animals repeatedly for a period of time. The duration of repeat-dose studies can be short (e.g., daily dosing for up to 14 days), subchronic (up to 3 months), or chronic (longer than 3 months and usually up to 2 years). An example of a study design for a 28-day repeat-dose toxicity study with a 28-day recovery period in rats is following-

6. Recommended Duration of Repeated-Dose Toxicity Studies to Support Marketing

7. Histological examinations of tissues commonly performed in single-dose and repeated-dose toxicity tests. Adrenal gland Peripheral nerve All tissue lesions Pituitary Aorta Prostate Bone with bone marrow Seminal vesicle Brain Skeletal muscle Epididymis Skin Esophagus Small intestine Eye Spinal cord Heart Spleen Kidneys Stomach Large intestine Testes Liver Thymus Lung Thyroid Mammary gland Trachea Mesenteric lymph nodes Urinary bladder Ovary Uterus Pancreas Vagina

8. Steps involved in Toxicity Testing

9. Factors Affecting Single and Repeated Dose Toxicity Species - The rat should normally be used for testing because it has been used extensively for toxicokinetic and toxicological studies. The use of other or additional species may be necessary if critical toxicology studies demonstrate evidence of significant toxicity in these species or if their toxicokinetics is shown to be more relevant to humans. Justification should be provided for the use of alternative or additional species . When the product administered is a pro-drug, its conversion to the active substance should be demonstrated in the species under study. Sexes - A minimum of four animals of one sex should be used for each dose tested. If there are data available that demonstrate substantial differences in toxicity between males and females, the more sensitive sex should be chosen. If there are no such data, then the use of both sexes (four males and four females) is strongly recommended. Justification should be provided for the sex of the animals used.

10. 3. Route of Administration - In general, the medicinal product should be administered by the same route as that intended for humans. Other routes of administration may be selected, if justified based on pharmacological, pharmacokinetic/toxicokinetic and/or toxicological information. In addition to systemic toxicity, effects at the site of administration, and if different, the intended clinical site of administration should be evaluated. 4 . Dose levels - a low dose, sufficient to produce the desired therapeutic effect or result in systemic exposure comparable with that expected at the intended clinical use. A high dose, selected to enable identification of target organ toxicity or other non-specific toxicity, or until limited by volume of dose. Limit doses for acute, subchronic, and chronic toxicity studies of 1000 mg/kg/day for rodents and non-rodents are considered appropriate in all cases except those discussed in the Guideline ICH M3 (R2). An intermediate dose, such as the geometric mean between the high and the low dose.

11. References OECD (2008),  Test No. 407: Repeated Dose 28-day Oral Toxicity Study in Rodents , OECD Guidelines for the Testing of Chemicals, Section 4, OECD Publishing, Paris, https://doi.org/10.1787/9789264070684-en . OECD (2010),  Test No. 417: Toxicokinetics , OECD Guidelines for the Testing of Chemicals, Section 4, OECD Publishing, Paris,  https://doi.org/10.1787/9789264070882-en . Kale, V. P., Bebenek , I., Ghantous , H., Kapeghian , J., Singh, B. P., & Thomas, L. J. (2022). Practical Considerations in Determining Adversity and the No-Observed-Adverse-Effect-Level (NOAEL) in Nonclinical Safety Studies: Challenges, Perspectives and Case Studies. International Journal of Toxicology, 41(2), 143–162 European Medicines Agency. (2009). ICH M3 (R2) Non-clinical safety studies for the conduct of human clinical trials and marketing authorization for pharmaceuticals.

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