This document discusses various methods for pharmacological and toxicological screening of substances. It provides details on: - Types of toxicity testing including acute, sub-acute, sub-chronic, and chronic toxicity tests. - Methods for determining lethal dose 50 (LD50) and lethal concentration 50 (LC50) values which represent doses/concentrations that are lethal to 50% of test subjects. - Specific acute oral toxicity testing methods like Karber's method, Miller-Tainter method, and up-and-down method. - Testing procedures which involve administering graduated doses of a test substance to rodents and making observations to determine health hazards.

1. (DEPARTMENT OF PHARMACOLOGY)
PHARMACOLOGICALAND TOXICOLOGICAL
SCREENING METHODS
• PRESENTATION TOPIC :
• Oral toxicity
• SUBMITTED TO : Dr NAGARATHNA P.K.M
• PRESENTED BY: DIANA MORIA

2. • Toxicology is the scientific study of adverse effects that
occur in living organisms due to chemicals. It involves
observing and reporting symptoms, mechanisms,
detection and treatments of toxic substances, in
particular relation to the poisoning of humans.

3. • Any undesirable &/ or unintended effects of drug,
• 1. Predictable (type A reactions)
• 2. Non-predictable (type B reactions)

4. • LD50 represents the individual dose
required to kill 50% of a population of test
animals. It is an index determination of
medicine and poison’s virulence. lower the
LD50 dose, the more toxic the pesticide.

5. • The concentrations of the chemical in air
that kills 50% of the test animals during the
observation period is the LC50 value.
Other durations of exposure (versus the
traditional 4 hours) may apply depending
on specific laws

7. • Karber’s method
• Miller and Tainter method
• Lorke’s method
• Fixed dose method
• UP and down method

8. • Acute toxicity 14 days
• Sub-acute (repeated doses) toxicity 28 days
• Sub-chronic toxicity 3 months
• Chronic toxicity 6 months to 2yrs
• Special toxicity e.g. Carcinogenicity

11. • Test substances :- at doses that are
known to cause marked pain and
distress due to corrosive or severely
irritant actions, need not be
administered.
• Moribund animals shall be humanely
killed.

12. • It is the principle of the test that, based on
a stepwise procedure with the use of a
minimum number of animals per step(3)
• sufficient information is obtained on the
acute toxicity of the test substance .
• .

13. • Selection of animal species:-
• The preferred rodent species is the rat,
although other rodent species may be
used. Normally females are used .
• should be nulliparous (8-12weeks)
wt_/+20
• Male can also be use if they shows better
sensitivity to the TS.

15. • The animals are randomly selected, marked to permit
individual identification, and kept in their cages for at
least 5 days prior to dosing to allow for acclimatisation to
the LC.

16. • TS:- should be administered in a constant
volume .
• Liquid sample should be use in undiluted form at
constant conc.
• Other vehicles can also be use
s/no dose Dosage form
1 1ml/100gBW liquid
2 2ml/100gBW Aqueous solution

17. • TS is given in a single dose using dose by gavage using
stomach tube .
• Its given in a smaller fraction over a period not exceeding
24hours
• Animal should fast prior to dosing

18. • 3 animals are use for each step
• Dose level to be used as the starting dose
is selected from one of the above 4 fixed
levels 5,50.300,2000mg/kg
• If there is no information about the
compound it is recommended to start using
300mg/kg

19. The limit test is primarily used in situations
where the experimenter has information
indicating that the test material is likely to be
nontoxic.
 Information about the toxicity of the test material
can be gained from knowledge about similar
tested compounds, taking into consideration the
identity and % of components known to be of
toxicological significance

20. • Observe the animal individually at for
30mins for period of 24hrs
• Special attention at the 1st 4hrs daily for
14days
• Time in which toxicity appears or
disappears is important and recovery
period.

22. • Data: all data should be summarize in a tabular form
containg the following information
Time
course of
death
No of
animal
used
No of
animals
found
death
No of
animals
killed for
human
reason
Time of
death

23. • Should contain the follow
• Test substance
• Vehicle
• Test animal
• Test condition

24. • Tabulation of response data and dose level
for each animal are noted .
• BW , time of sacrifice and time and date of
death.
• Histopathology and necropsy finding .

25. • In a study of toxic characteristics of
substance, acute oral toxicity testing is
initial step.
• Gives information on health hazards.
• Test substance administered orally, in
graduated doses to several groups of
experimental animals.
• One dose used per group.

26. • At least 5 rodents at each dose level of same
sex are used.
• Observations for effects & death are made.
• After completion of study in one sex, study in
another sex is carried out.
• Studies suggested in rodents but can be
adopted for studies in non-rodents.

27. • As 1st alternative to conventional
acute toxicity test. Testing in 1 sex
usually females is considered
sufficient.
• Uses fewer animals. Causes less
suffering to the animals.
• Uses only moderately toxic doses,
doses expected to be lethal should be
avoided

28. Principle of test substance
Description of method
Housing and feeding
Preparation of animal
Preparation of dose
Dose administration

29. • Procedure involves 2 step study
• 1- sighting study
• 2-main study

30. • Purpose : to allow selection of appropriate
starting dose
• For the main study.
• Single dose is administered in a sequential
manner.
• Sighting study is completed when decision on
starting dose is done

31. • No of animal and dose level
• Usually 5 animals are use
• Limit test
• Observation same
• report

32. • Up and down testing approach was 1st
described by Dixon and Mood.
• Bruce in 1985 proposed to use it for acute
toxicity determination of chemicals .
• Estimates confidence intervals for LD50

33.  In procedure (main test ) 1-animal dosed at a
time, at minimum of 48hrs interval.
Suggested starting dose is 175 mg/kg or can be
selected from 1.75, 5.5, 17.5,
55,175,550,2000mg/kg .
 Animal receives 1st dose a step below the level
of the best estimate of LD50 .

34. • consist of a single ordered dose
progression in which animal are dose
and kept for minimum of 48hrs
• First animals receive dose step below
level of best estimate of LD50 if
animal survives next dose is increase
by factor of 3.2times original dose
• And decreases if animal dies.

35. • Limit test for 2000
• Limit test for 4000
• Limit test for main test

36. • Its calculate using likelihood method ,
following dixion .assume 𝜕 as death or
delay death
• L=L1L2………Ln
• Li=1-f(Zi) if animal survives
• Li =f(zi) if animal dies
• Where Zi=⟮log (di)- µ ] ̸ 𝜕 di]

37. • After main test and estimation of
LD50 its possible to compute the
interval estimates for LD50.
• The wide confidences interval should
be narrow
• If main test is repeated should be
close to the original value
• Test report

39. Hyposalivation/Xerostomia
Xerostomia, also known as dry mouth
and dry mouth syndrome, is dryness in
the mouth, which may be associated with
a change in the composition of saliva, or
reduced salivary flow, or have no
identifiable cause

40. • It is an immune mediated process where Tcells
mediate the destruction of the basal cells of the
epithelium,
• Its while associated with erythema and ulcer
• Often occurs in buccal mucosa, tongue and
gingiva.

42. • Its rare in oral cavity ,usually occurs on skin.
• Occurs due to autoimmunity
• Antipsychotics .spironolactone and
sulphonamide
•others

43. •Thank You