This document discusses various types of animal toxicity studies that are required before a drug can be administered to humans. It describes how these studies help establish the therapeutic index and predict adverse effects in humans. The key types of studies mentioned are systemic toxicity studies (including single dose, repeated dose, reproductive, and local toxicity), allergenicity/hypersensitivity studies, genotoxicity studies, and carcinogenicity/oncogenicity studies. Each type of study has specific objectives, test models used, parameters evaluated, and methods for conducting the studies and evaluating results. The studies aim to assess benefits and risks of drugs and establish their safety profiles before human use.

1. ANIMAL TOXICITY STUDIES
Dr.k.vishnuvardhan babu

2. Why study toxicology???
Benefit –risk ratio can be calculated
Prediction of therapeutic index
Therapeutic index= Maximum tolerated dose
Minimum curative dose
Smaller ratio, better safety of the drug

3. why do we require non clinical
studies IN ANIMALS before
ADMINISTERED to man??
 Pharmacological effects are same in man as in animals
 Toxic effect in species will predict adverse effects in man
 Giving high doses in animals improves predictability to man
 Risk assessment can be made by comparison of toxic doses
in test species with predicted therapeutic dose in man

4. Relevant Test Models
 Pharmacodynamic responses
 Pharmacokinetic profile
 Species, sex, age of experimental animals
 Susceptibility, sensitivity and reproducibility of test
system
 In vitro: Isolated organs, tissues cell-cultures
 Mechanism of effect in vivo

5. Types of toxicology studies
Systemic toxicology studies
Single dose studies Repeated dose studies
Reproductive toxicology studies
Male fertility Female reproduction & Developmental
studies
Local toxicity studies
Hypersensitivity studies
Genotoxicity studies
Carcinogenicity studies

6. A. Systemic toxicology studies
Preliminary Definitive
• Maximum Non
Lethal dose
(MNLD) determined
• MTD and MLD
determined
• Evaluate effects
• Target organ of toxicity
may be determined
a) SINGLE DOSE STUDIES/ ACUTE TOXICITY

7. Preliminary studies
METHOD
 Single dose tested in 2 rodent species
 2 routes of administration
 Oral dosing of 2g/kg or 10 times of normal human dose
 Observation for 14 days after dosing
 MNLD established
 Symptoms , signs reported
 Microscopic and Macroscopic evaluation

8. Definitive studies
METHOD
 Group of 20 animals of either sex dosed at MNLD
 5 animals of each sex are observed for 48 hr and
conduct autopsy for early pathological changes
 Remaining 5 of each sex are observed for 14 days
 MTD and MLD established
 Signs of intoxication or recovery, changes in body
weight, pathological changes
 Complete macroscopic and microscopic examination
 Target organs can be identified

9.  Two mammalian species(one should be non-rodent)
 Long duration studies (30-180 days)
 Dose is dependent on dose-escalating studies
 Drug administered by clinical route
 Parameters monitored and recorded are:
 Behavioral
 Physiological
 Biochemical
 Microscopic observations
b) REPEATED DOSE STUDIES/SUB-ACUTE
OR CHRONIC TOXICITY

10. Chronic toxicity
 Objectives
 To evaluate the cumulative toxicity of chemicals.
 To assess carcinogenic potential.
 Duration
Rodents - 6 to 24 months; non-rodents - 12 months or longer
or up to 15 to 20% of species’ lifespan.
 Test System/Animal System
2 species required. Rodents, non rodents.
 Parameters
 Mortality
 Pathology and histopathology
 Weight change
 Clinical pathology of all animals (mortalities and
survivors)

11. B. Reproductive toxicology studies
a) MALE FERTILITY
METHOD
One rodent species(rat)
3 dose groups taken
(each with 6 adult males),
1 control
Drug treatment by clinical route for 28-72 days

12. Mated with females in 1:2 ratio
Females getting pregnant should be examined
After 13 days of gestation
All male animals sacrificed
•Weights of testis, epididymus recorded & examined for
their histology
•Sperms examined for motility & morphology

13. Segment I
13
Fertility and general reproductive
performance study
Segment II Teratogenicity
Segment III Perinatal and post-natal study
Fertility and early embryonic
development (rat)
Embryo- foetal development
(rat & rabbit)
Post natal development (rat) (post natal
survival of offspring), growth parameters,
vital senses, behavioral effects
b) FEMALE FETILITY
Drug administered to both males (28days) and females
(14 days) before mating
Implantation
Embryogenesis

14. C. Local toxicity studies
 Required when drug is administered by special
route (other than oral) in humans
 Study design:
 2 species along with control used
 Dose dependent on dose escalating studies
 3 dose levels

15. Types of local toxicity studies
Dermal toxicity studies
 Dermal photo-toxicity
studies
Vaginal toxicity studies
Rectal tolerance studies
Rats & Rabbit
Local signs (erythema, oedema),
histological examination
Guinea pig
Used in treatment of leucoderma
Examination of erythema &
oedema formation
Rabbit or Dog
Observation of swelling,
histopathology of vaginal wall
Rabbit or Dog
Signs of pain, blood or mucous,
histology examination of rectal
mucosa

16. Ocular toxicity studies
Parenteral drugs
Inhalation toxicity studies
Albino Rabbit
Changes in cornea ,Iris &
aqueous humor, histological
examination of eye
For intravenous/
intramuscular/ subcutaneous/
intra-dermal injection
Sites of injection examined
grossly and microscopically
One rodent and non rodent
species
Acute , sub-acute and chronic
studies performed
Observation of respiratory rate
Histological examination of
respiratory passages, lung tissue

17. D. Allergenicity/hypersensitivity
toxicology studies
Guinea Pig
Maximization test
Local lymph node assay
Determination of Maximum non
irritant or minimum irritant dose
Evaluation of Erythema and
oedema
Mice of one sex(either male or
female)
Drug treatment given on ear skin
Auricular lymph node dissection
after 5 days
Increase in 3h-thymidine used for
evaluation

18. E. Genotoxicity studies
To detect early tumorigenic effects in cases of chronic
illness
In vitro tests:
Test for gene mutation in Bacteria
Cytogenetic evaluation of chromosomal damage in
mammalian cells
E.g.; Ames’s Salmonella Assay detects increased
number of aberrations in metaphase chromosomes
DNA strand breaks, DNA repair or recombination,
Measurements of DNA adductsIn vivo tests:
Chromosome damage in rodent hematopoietic cells
E.g.; Micronucleus Assay

19. f. Carcinogenicity/ oncogenicity studies
Life-time Bioassays
Carcinogenicity studies are performed on:
Drug used for >6 months or frequent intermittent use for
chronic diseases
Chemical structure of drug indicates carcinogenic
potential
Therapeutic class of drugs which have produced positive
carcinogenicity

20. Group sizes of 50 animals/sex at each of 3 dose
levels
Control group is of double size
Record for onset of tumor development
Usually carried out for 24 months in rats and 18
months in mice (life span studies)
CONDUCT OF STUDY

21. EVALUATION OF RESULT
Incidence of cancers in control and test
 Trend towards increasing incidence with
increasing doses
Number of animals with single/multiple tumors
Macroscopic changes observed by autopsy
 Histopathology of organs and tissues

22. Thank you