A drug that selectively relieves pain by acting in the CNS and Peripheral pain mechanism without significantly altering consciousness

1. SCREENING
OF
ANALGESICS & ANTIPYRETIC

2.  INTRODUCTION
 CLASSIFICATION
 SCREENING OF NARCOTIC ANALGESIC
 SCREENING OF NON-NORCOTIC ANALGESIC
 SCREENING OF ANTIPYRETICS
 REFERENCES

3. ANALGESICS:
A drug that selectively relive pain by acting in
the CNS and Peripheral pain mechanism
without significantly altering consciousness.

4. ANALGESICS
NARCOTICS
NON-
NORCONICS

5. Principle:-
Record the response of an animals to a painful
stimulus before and after administration of
analgesics.
Methods
Mechanical Thermal Others

6.  Tail clip method:
 Animals: Mice/Rats
 Instruments: Artery clamp, stop watch
 Group: 6-10 Mice
 Test substances: 12.5mg/kg morphine HCl via s.c
 Procedure:
Test sensitivity of animal to artificial pain
produced by clipping artery clamp(not exceeding 15 sec).

7. Administration of dose via s.c route
Test sensitivity of animal to artificial pain at
30,60,90 min observed
If no attempt to remove the clip is made during
15sec at one of the three observations
Positive analgesic response

8.  Hot Plate Method:
 Material
 Animal: Mouse
 Instrument: Hot plate analgesiometer
 Painful stimulus: Heat (55°C)
 Drug used: 0.63 mg/kg Morphine via s.c

9. Mice dropped on hot plate( 55°C)
The reaction times taken i.e. at nearest fifth of second, 5min, 10min before drug
administration(normal time)
Drug administered s.c
Reaction time taken at 10 , 20 , 30 , 45 , 60,90,120,180 and 240min
The response considered positive when reaction time after drug administered is
longer than 30 sec at least once
Positive analgesic action

10.  Material
 Animal: Mouse
 Instrument: Tail-flick analgesiometer
 Painful stimulus: Heat (by applying a beam of light 130°C)
 Drug used: 4mg/kg Morphine hydrochloride via s.c route

11.  This test is designed to show morphine like
properties in a drug.
 Animals: Male rats
 Procedure:
Toxic dose of a drug was injected to the animals
Peak effects are observed
0.5- 10.0 mg/kg nalorphine inj via i.v route
Reduces the toxicity

12.  Animals: Grp of 20 mices.
 Drugs used: 2,4,8mg/kg pethidine ,
Test substance (25% of LD₅₀).
 Procedure: Grp of 20 mice are divided into half-
groups of 10 for each of three doses of pethidine:
2,4,8mg/kg.
 The other half given pethidine and test substance.
 The percent analgesia is calculated with the aid of a
thermal test.

13.  Writhing Method:
Principle:
The painful stimulus is induced by IP injection of an
irritant substance (e.g.300mg/kg of 3% acetic
acid) .

14.  Material
 Animal: Mouse
 Painful stimulus: Chemicals e.g.300mg/kg of 3% acetic
acid
 Drug used: NSAID e.g. Na salicylate
 Procedure:
Grp of 6 mice taken
i.p inj of 300mg/kg of 3%acetic acid given
Writhing observed(control)

15. Test substance given orally 15min prior to acetic
acid
Total no of stretching episodes observed for 20
min
No of writhing observed is less compared control
Positive analgesic action

16. Brewer’s yeast suspension method:
Procedure:
Taken rats avg wt (150-200gm)
Body temp recorded by rectal thermometer
15% Brewer’s yeast + 0.9% saline sol inject rat subcutaneously &
placed for 18 hrs.
When body temp rises test drug given
Record response at 30,60,120,180 min

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