Repeated dose toxicity study

This study is also called as

"Subacute toxicity study"

This is an important study to test the safety of an chemical during the drug discovery process.

Transcript

1. Repeated Dose Toxicity studies (Subacute/Sub-chronic toxicity study) Oral, Dermal and Inhalation routes Dr. K. Nandakumar Professor, Department of Pharmacology MCOPS, MAHE, Manipal
2. Objectives of this Presentation • The presentation will help the students of Master of Pharmacy (Pharmacology and related disciplines) to comprehend the topic– ”Sub-acute toxicity studies” , in their curriculum. [PCI syllabus: Toxicological Screening Methods (MPL202T)]. • To describe how subacute toxicity studies are performed in industries, to meet regulatory requirements. • Describe OECD 407, 410 and 412 guidelines pertaining to repeated dose toxicities of test chemicals administered via oral, dermal and inhalation routes.
3. Generally we adopt OECD guidelines (1) The initial guidelines were published in 1981 (2) Revised in 1995 to include neuro and immunotoxicities. (3) Ammended in 1998, to obtain information related to endocrine disruptors Oral route – Guideline no. 407 [28 d], 408 [90 d] (Rodents), 409 (Non-rodents) Dermal route – Guidelines no. 410 [28 d], 411 [90 d], Inhalation route – Guidelines no. 412 [28 d], 413 [90 d].
4. Principle of the Test OECD 407 OECD 410 OECD 412 Test substance administered once daily, by oral route, for 28 d. Animals observed closely, each day for signs of toxicity Test substance administered dermally for 28 days. Observed closely, each day for signs of toxicity Test substance - inhalation administered for a defined period. Observed closely, each day for signs of toxicity Establish dose dependent relation-ship for the toxic effect Allows to determination of the No-Observed Adverse Effect Level (NOAEL) and provide information on selection of doses for long term studies
5. Selection and Preparation of Animals OECD 407 OECD 410 ECD 412 Rats are the preferred species. Lower species - increase variability: dissecting smaller organs. Other species are accepted under suitable justification. Young healthy adult animals of commonly used laboratory strains should be employed. Females should be nulliparous and non pregnant. The strain which has be adopted shall be in accordance to the chronic study. Dosing should be initiated as early after the weaning period. At any case dosing should not be delayed more than 9 weeks old. Body weight variation should not exceed greater than 20%
6. Housing and Selection of doses Husbandry conditions similar to Acute toxicity studies: Temperature – 19 to 25o C, RH – 55%- 65% ; Light : dark- 12:12, Free access to standard pellet and potable drinking water Selection of doses: (Minimum 3 doses) First High dose is decided - - This dose should induce toxic effect but not severe toxicity or death - Toxicokinetic data, SAR, Previous experience, Efficacy study, LD10 may help in predicting this dose High Dose Low Dose Medium Dose - Usually 2 to 4 times reduced as compared to the highest dose levels. - Preferentially falls on the human exposure dose. - Should not produce any observed toxic effect - May be 10 times lower than the medium dose levels or higher dose levels
7. Grouping and number of animals 25 males + 25 Females Control (5 M+ 5F) Low dose (5 M+5F) Medium dose (5M+5F) High dose (5M + 5F) Satellite receives high dose (5M+5F) 5 groups Additional animals can be kept in each group if interim sacrifices are planned. Exposure to various routes is as per acute toxicity exposure. Satellite groups helps to identify delayed type of toxicity and withdrawal effects. Limit dose studies can be done at 1000 mg/kg
8. Mode of exposure of Test substance OECD 407 Oral route OECD 410 Dermal route OECD 412 Inhalation route Test substance - orally administered for a defined period. Observed closely, each day for signs of toxicity Test substance - skin administered for a defined period. Observed closely, each day for signs of toxicity Test substance - inhalation administered for a defined period. Observed closely, each day for signs of toxicity
9. Observations Daily observations: Clinical observations, General health record of animals, Mortality and morbidity – Preferably at the same time on each day and at anticipated peak period Weekly observations: - Body weight changes, Food and water intake - Behavioral, neurological and autonomical profiles End observations: - Functional observations like grip strength, auditory, visual stimuli etc. - Vaginal smears, Blood collection, Gross necropsy and organ collection - Additional Blood sampling can be done to establish Toxicokinetics and pharmacokinetics as per ICH guidelines
10. Parameters assessed - Hematological parameters - Clinical biochemistry - Targeting to assess liver, kidney and heart functions - Metabolic profiles and electrolyte balance - Hormones and Endocrine related endpoints - Wet weight of organs - All the major weighable organs shall be weighed - Expressed in terms of organ indices - Gross necropsy and Histology of all the Organs. - Satellite group will undergo the same procedure after 14 days of post treatment. [28 +14 d] - Reporting
11. THANK YOU