This document provides an overview of toxicity testing methods for acute, subacute, and chronic toxicity studies. It discusses the importance and history of toxicity testing, as well as standard methods and guidelines established by organizations like OECD and EPA. A variety of in vivo and in vitro toxicity tests are described, including acute, repeated dose, genotoxicity, carcinogenicity, and local toxicity studies. The document also addresses the large number of animals used annually for toxicity testing globally and the regulatory framework for animal testing in India.

1. ANIMAL TOXICITY TEST FOR ACUTE,
SUBACUTE & CHRONIC TOXICITY.
PRESENTED BY
SINDHU K
MVSC SCHOLAR,
DEPT OF VPT, COVAS.

2. TOXICITY STUDIES - INTRODUCTION
• Toxicology classically has been defined as the study of poisons & concerned with the
adverse effects of xenobiotics.
• Casarett 1996 defined it as a science that defines the limits of safety of chemical
agents for human & animal populations.
• Toxicological screening is very important for the development of new drugs and for
the extension of the therapeutic potential of existing molecules.
• The US-FDA states that it is essential to screen new molecules for pharmacological
activity and toxicity potential in animals (21CFR Part 314).
• Toxicity tests are mostly used to examine specific adverse events or specific end
points such as cancer, cardiotoxicity, and skin/eye irritation.
• Toxicity testing also helps calculate the No Observed Adverse Effect Level (NOAEL)
dose and is helpful for clinical trails.

3. HISTORY OF TOXICITY STUDIES
• Paracelsus (Father of Toxicology): determined specific chemicals responsible
for the toxicity of plants and animals (dose-response relationship).
• "All substances are poisons; there is none which is not a poison. The right
dose differentiates a poison and a remedy”
• Paracelsus
• Mathieu Orfila, determined the relationship between poisons and their
biological He is referred to as the father of modern toxicology.

4. SOURCES OF TOXIC SUBSTANCES
• Classified based on their
• chemical nature
• mode of action
• class (exposure class and use class)
• Exposure class: Food, air, water or soil.
• Use class: drugs as drug of abuse, therapeutic drugs, agriculture chemicals,
food additives, pesticides, plant toxins and cosmetics

5. EVIDENCES
The use of sheep brain for the production of rabies vaccine has been
phased out in 1992
Classical swine fever virus vaccine is produced in PK-15 Cells instead using
large number of rabits
PPR, FMD and sheep pox vaccines are also produced using cell culture vero,
BHK-21 and vero cell culture system respectively.
The use of laboratory animals e.g., rabbit and G. pig has been now
abandoned for the isolation or typing of mycobacetria with the availability
of improved synthetic media.

6. BIOMEDICAL ETHICS
• Before conducting any toxicological testing in animals or collecting
tissue/cell lines from animals, the study should be approved by the
Institute Animal Ethics Committee (IAEC) or the protocol should
satisfy the guidelines of the local governing body.

7. NECESSITIES OF TOXICOLOGICAL STUDIES
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.

8. MAGNITUDE OF USE OF ANIMALS
It has been estimated that approximately 20 million animals are being
used for testing and are killed annually; about 15 million of them are
used to test for medication and five million for products.
China has become one of the biggest countries using lab animals, as is
evident in the higher numbers and quality of lab animals (e.g., specific
pathogen free, or SPF1; genetically modified) increasingly used in
scientific research—16 million a year, compared to 12 million in the 25
European Union countries in 2005 (FELASA 2007)—and the increased
publication of animal experiment results in international journals.

9. ,
Japan was second only to the US, which used 17.3
million animals in 2005. The third largest use in
2005 was Great Britain, which used 1.9 million
animals.
People for the ethical treatment of animals (PETA)
reported that the National Centre for Laboratory
Animal Sciences (NCLAS) in Hyderabad, supplies
approximately 50,000 animals to laboratories every
year and to 175 institutions in India, including
pharmaceutical companies and educational
institutions.

10. ,
In India, among rodentia group of animals e.g. mice. rat, G.pig, rabbit,
mice is predominantly used in most of cases followed by other rodentia.
The number of monkeys used in research has now drastically reduced in
institutions.
Use of some other unique animals like hamster, cotton rat, gerbil is not
much common.
There are inbred strains of mice which are used for research and
genetically modified laboratory animals are also imported into India by
some of institutes.
The information with regard to available laboratory animals resource in
different institutions/universities in India is not precisely known.

11. Standard Methods
 Multiple methods have been standardized (certified) by multiple
organizations
 American Society for Testing and Materials (ASTM)
 Organization for Economic Cooperation and Materials (OECD) –
(Europe based)
 National Toxicology Program (NTP)
 All above standardized protocols available from US EPA,
Federal Register and researchers that developed the programs

12. REGULATORY MECHANISMS IN INDIA
• Institute Animal Ethics Committee (IAEC)
• Committee for the Purpose of Control and Supervision of Experiments in
Animals (CPCSEA)
• Drugs & Cosmetics Act, 1940, Appendix-I
• Department of Animal Husbandry, Dairying & Fisheries, Ministry of
Agriculture, New Delhi-2001
• Department of Biotechnology.
• The Prevention of Cruelty to Animals Act, 1960 as amended up to 30th
July 1982 and Animal Welfare Board

13. RELEVANT TEST MODELS
Pharmacokinetic profile
Pharmacodynamic response
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

14. In vivo
toxicological
models

15. IN-VIVO >< IN-VITRO
1.In Vivo Studies
In vivo safety pharmacology studies should be designed to define the
dose-response relationship of the adverse effect observed
The time course of the adverse effect should be investigated
e.g. onset and duration of response
2.In Vitro studies
In vitro studies should be designed to establish a concentration-effect
relationship

16. TYPES OF TOXICITY STUDIES
• Single dose studies/ Acute toxicity studies
• Repeated dose studies / sub-acute or Chronic studies
• Local toxicity studies
• Allergenicity / Hypersensitivity toxicology studies
• Genotoxicity studies
• Carcinogenicity / Oncogenicity studies

17. 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

18. ,• Acute toxicity testing- study the effect of a single dose on a
particular animal species.
• Acute toxicity testing be carried out with two different animal
species (one rodent and one non-rodent).
• In acute toxicological testing, the investigational product is
administered at different dose levels, and the effect is observed for
14 days. All mortalities caused by the investigational product during
the experimental period are recorded and morphological,
biochemical, pathological, and histological changes in the dead
animals are investigated.

19. ,
• The LD50 was used as an indicator of acute toxicity previously. The
determination of the LD50 involves large numbers of animals, and the
mortality ratio is high. (24 h testing)
• Graphical method
• Arithmetical method (karbers’s) method. when number of animal is small)
Because of these limitations, modified methods
were developed:
1. The fixed dose procedure
2. The acute toxic category method
3. The up-and-down method

20. Test report
The test report should include the following information:
• Test substance:
• Physical nature,
• Purity
• Physicochemical properties;
• Identification data;
• Source of substance;
• Batch number

21. CONTD
Vehicle (if appropriate):
• Justification for choice of vehicle (if other than water).
Test animals:
• Species/strain used and justification for choice made;
• Number, age, and sex of animals at start of test;
• Source, housing conditions, diet, etc.;
• Individual weights of animals at the start of the test.

22. OECD
Organization for Economic Cooperation and Development (OECD)Test
Guidelines (TGs 402, 403, 420, 423, and 425) describe acute systemic testing.
• Fixed Dose Procedure (OECDTG 420)
• AcuteToxic Class method (OECDTG 423)
• Up‐and‐Down Procedure (OECDTG 425)
• Acute DermalToxicity (OECDTG 402)
• Acute inhalation toxicity (OECDTG 403)

23. Six OECDTest Guidelines describe short‐term repeat‐dose toxicity
testing
• Repeated Dose 28‐day OralToxicity Study in Rodents (TG407)
• Repeated Dose 90‐Day OralToxicity Study in Rodents (TG 408)
• Repeated Dose DermalToxicity: 21/28‐day Study (TG 410)
• Sub-chronic DermalToxicity: 90‐day Study (TG 411)
• Repeated Dose InhalationToxicity: 28‐day or 14‐day Study (TG 412)
• Sub-chronic InhalationToxicity: 90‐day Study (TG 413)

24. 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

25. .• Rodents and non-rodents are used to study the sub-chronic toxicity of a substance.
• Dose: Expected therapeutic level (daily) or expected therapeutic level to increasing dose
phase-wise manner.
• The test substance is administered orally for =/>90 days, and regular body weight
variations, biochemical and cardiovascular parameters changes, and behavioral changes
are observed.
• At the end of the study, the experimental animals are sacrificed. Gross pathological
changes are observed, and all the tissues are subjected to histopathological analyses.
• There should be little individual variation between the animals, and the allowed weight
variation range is ±20%.
• Used to determine the maximum tolerable dose and nature of toxicity.

26. .Chronic toxicity studies are conducted with a minimum of one
rodent and one non-rodent species.
• The test compound is administered over more than 90 days, and the animals
are observed periodically.
• A chronic toxicology study provides inferences about the long-term effect of
a test substance in animals, and it may be extrapolated to the human safety
of the test substance.
• The report on chronic oral toxicity is essential for new drug entities. There
should be little individual variation between the animals, and the allowable
weight variation range is ±20%.

27. DOSE
• High dose: Produce significant retardation of growth or some
pathological changes (10 times the expected maximum clinical
dose).
• The low dose is about twice the expected maximum clinical dose
• Third dose is medium dose fixed midway between the high and
low dose

28. .• During the study period, the animals are observed for normal
physiological functions, behavioral variations and alterations
in biochemical parameters at regular intervals (atleast every
14 days).
• At the end of the study, tissues are collected from all parts of
the animal and subjected to histological analyses.

29. 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

30. 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

31. 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

32. 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

33. IN VIVO TESTS
 In vivo test for chromosomal damage using mammalian
hematopoietic cells.
 Chromosome damage in rodent hematopoietic cells
E.g.; Micronucleus Assay

34. 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

35. NOTE ON STEM CELLS
STEM CELLS NOW EMERGING AS AN ALTERNATIVE TO LABORATORY ANIMALS Drug company
interest in stem cell drug testing was demonstrated in July 2008, when GlaxoSmithKline
entered into a $25 million-plus agreement with the Harvard Stem Cell Institute.
By testing drugs on specific cells and tissues created from iPS cells, we can even predict a
patients individual response to a treatment realizing the vision of personalized medicine.
In the current issue of Stem Cells and Development (2007), Cezar and her colleagues revealed
a novel way to test drug toxicity: by monitoring the behaviour of embryonic stem cells
exposed to a drug-candidate compound.
Studying how potential drugs affect embryonic stem cells could provide a far more accurate
prediction of a drug's potential toxicity than conventional animal models can.
Currently, the most successful development of stem cells as in vitro models for toxicology
testing is in human cardiac tissue.

36. ,

37. OECD GUIDELINES FOR ACUTE, SUB-CHRONIC & DERMAL
TOXICITY STUDIES
ACUTE
• 401 ~ Acute Oral Toxicity
• 402 ~ Acute Dermal Toxicity

38. SUB CHRONIC
• 407 ~ Repeated Dose Oral Toxicity ( Rodents : 28 days / 14 days study )
• 408 ~ Sub-chronic Oral Toxicity Test ( rodents : 90 days study )
• 409 ~ Sub-chronic Oral Toxicity Test ( Non-rodents : 90 days study )
• 410 ~ Repeated Dose Dermal Toxicity ( 21/28 days study )
• 411 ~ Sub-chronic Dermal Toxicity (90 days study )

39. CHRONIC
• 452 ~ Chronic Toxicity Studies
• 453 ~ Combined Chronic Toxicity/Carcinogenicity studies

40. DEFINITIONS RELATIVE TO DOSES
ACUTE STUDIES
ED 50 : The median effective dose = the dose for which
half(50%) of the animals exhibit an effect (E) and half of
animals exhibit no effect
LD 50 : The median lethal dose = the effect may be defined as
specific toxic event (tremors) & sometimes defined as lethality
ED10 & ED90 are doses at which 10% & 90% of the animals
respectively demonstrate effect

41. GENERAL STUDIES
• LIMIT DOSE : a dose which is considered high enough that if no mortality /
significant toxicity is seen in animals receiving this dose, no higher doses are
required
eg : Limit doses(EPA/OECD)
1.Acute Oral Toxicity 5000mg/kg
2.Acute Dermal Toxicity 2000mg/kg
3.21-days Dermal Toxicity 1000mg/kg
4.Chronic Studies of Pesticides 1000mg/kg
Note: the limit dose of a non-nutritive material added to diet is generally
considered to be 5% (50,000ppm)

42. SUB-CHRONIC & CHRONIC STUDIES
• ADI: Acceptable Daily Intake (established for food
additives/ residues & published by EPA)
• NOEL: No Observed Effect Level. Dose at which no effect is
seen
• NOAEL: No Observed Adverse Effect Level. Dose at which
no adverse/toxic effect is seen

43. CHRONIC STUDIES
• MTD: Maximum Tolerated Dose. Is the highest dose that can be tolerated
without significant lethality from causes other than tumors.
(for EPA studies MTD for chronic studies with pesticides is a dose which
produces an approximate 10-15% decrement in body weight gain)
• HTD: Highest dose tested. Highest dose that can be expected to yield
results relevant to humans. This is a proposed new dose which would be
selected based on evaluation of results of sub-chronic studies.

44. VEHICLES USED FOR DOSING
• ORAL: Water, Methylcellulose or Carboxymethylcellulose(0.5-5%
aqueous suspension), Oil( corn, peanut, sesame)
• DERMAL: Physiological saline, Water, Ethanol, Acetone, Mineral
oil
• PARENTERAL: Physiological saline(sterile), sterile water for
injection

45. CLINICAL SIGNS OF TOXICITY
RESPIRATORY: blockage in the nostrils, changes in rate & depth of
breathing, changes in color of body surfaces
• Signs like dyspnea, abdominal breathing, gasping, Apnea, Cyanosis,
Tachypnea, nostril discharge = involvement of CNS respiratory
center, pulmonary edema, cholinergic inhibition, pulmonary cardiac
insufficiency.

46. MOTOR ACTIVITY
Changes in frequency & nature of
movements
Signs like decrease/increase in
spontaneous motor activity,
Somnolence, Loss of righting reflex,
Anesthesia, Catalepsy, Ataxia, Unusual
locomotion, prostrations, Tremors &
fasiculations = CNS, sensory, autonomic
& neuromuscular system

47. CONVULSIONS
Marked involuntary contractions or seizures of contraction of
voluntary muscles
Signs like Clonic convulsions, Tonic convulsions, Tonic-Clonic
convulsions, Asphyxial convulsion, Ophisthotonos = CNS, respiratory
failure, neuromusculsr & autonomic systems.

48. REFLEXES
• CORNEAL
• PINNAL
• RIGHTING
• MYOTACT
• LIGHT(pupillary)
• STARTLE REFLEX
All signs indicates involvement of CNS, sensory, autonomic &
neuromuscular systems

49. OCULAR SIGNS
• Lacrimation, Miosis, Mydriasis, Exophthalmos, Ptosis,
Chromodacryorrhea ( red lacrimation ), relaxation of nictating
membrane, corneal opacity, iritis, conjunctivitis.
Mainly due to autonomic system involement

50. CARDIO-VASCULAR SIGNS
• Bradycardia, tachycardia, vasodilation, vasoconstriction,
arrhythmias
• Due to autonomic, CNS, cardiac-pulmonary insufficiency,
myocardiac infarction, cold environment.

51. OTHER SIGNS
• Salivation
• Piloerection
• Analgesia
• Muscle tone - hypotonia
- hypertonia
• GIT signs: dropping feces, emesis, diuresis(hematuria &
involuntary urination)

52. AUTONOMIC SIGNS
• Sympatomimetic – piloerection, partial mydriasis.
• Sympathetic block – ptosis, diagnostic if associated with sedation.
• Parasympathomimetic – salivation, miosis, diarrhoea.
• Parasympathomimetic block – mydriasis (maximum), excessive
dryness of mouth.

53. TOXIC SIGNS OF ACETYLCHOLINESTERASE INHIBITION
MUSCARINIC EFFECTS NICOTINIC EFFECTS CNS EFFECTS
Bronchoconstriction,
Increased
bronchosecreation.
Muscular twitching Giddiness, anxiety,
headache
Nausia & Vomiting Fasciculation Apathy , confusion
Diarrhea Cramping Depression, drowsiness,
seizures,
Bradycardia Muscular weakness Ataxia
Hypotension Respiratory depression
Miosis confusions
Urinary incontenance coma

54. EFFECTS OF DECREASED BODY WEIGHTS ON RELATIVE
ORGAN WEIGHTS OF RATS
• Decreases = liver
• No change = heart, kidneys, prostrate, spleen, ovaries.
• Increases =adrenal gland, brain, epididymides, pituitary,
testes, thyroid, uterus.

55. Human studies
1. General considerations for clinical studies
2. Specific considerations for clinical studies
a. Protocol design
b. The study population
c. Statistical analyses
3. Sequence of clinical studies
a. Early clinical studies
b. Further clinical studies
4. Submitting reports of clinical studies to CFSAN (Center for Food
Safety and Applied Nutrition)

56. PHASES OF DRUG DEVELOPMENT
(ANIMAL MAN)
PHASE III PHASE IV
PHASE I
PHASE IPRECLINICAL PHASE II
Product Approval
(NDA/MAA)
Patient studiesEntry to man
(IND / CTA)
None
Healthy subjects
Safety and
tolerability
Genetic toxicity
(in vivo)
Repeat dose
toxicity testing
+
Bioanalysis /
Toxicokinetics
Drug Metabolism
Reproductive
Toxicity Testing
(teratogenicity)
Patients
Small scale
efficacy studies
Patients
Large scale
multicentre
studies
Chronic (long term) toxicity testing
+
Bioanalysis / Toxicokinetics
Reproductive Toxicity Testing
(fertility and pre/post natal)
Carcinogenicity studies
Drug Metabolism
Patients
Large scale
post-marketing
studies
As required
Genetic toxicity
(in vitro)
Single / repeat dose
toxicity studies
+
Bioanalysis /
Toxicokinetics
Safety Pharmacology
Drug Metabolism
Lead candidate
Identified
Non-clinical
MOLECULE

57. DISCUSSION SESSION
• ,

58. REFERENCES
• CRC hand book of toxicology
• Google images & Wikipedia
• Online Related materials from slideshare

59. THANK YOU