PRANESH KUMARM.PHARM

BBAU LUCKNOW

SCREENING OF

ANALGESICS & ANTIPYRETIC

INDEX:

INTRODUCTION

CLASSIFICATION

SCREENING OF NARCOTIC ANALGESIC

SCREENING OF NON-NORCOTIC ANALGESIC

SCREENING OF ANTIPYRETICS

REFERENCES

INTRODUCTION:

ANALGESICS: A drug that selectively relive pain by acting

in the CNS and Peripheral pain mechanism without significantly altering consciousness.

CLASSIFICATION:

ANALGESICS

NARCOTICS NON-NORCONICS

Screening of Narcotic Analgesics :

Principle:-Record the response of an animals to a painful

stimulus before and after administration of analgesics.

Methods

Mechanical Thermal Others

MECHANICAL METHODS:

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).

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

Thermal methods:

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

PROCEDURE: 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.cReaction 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

Tail-flick method:

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

Nalorphine antagonism : 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

Pethidine potentiation:

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.

Writhing Method:Principle:The painful stimulus is induced by IP injection of an

irritant substance (e.g.300mg/kg of 3% acetic acid) .

Screening of Non-narcotic Analgesics:

Writhing method: 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)

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

SCREENING OF ANTIPYRETICS:

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

REFERENCES:

Pullaiah T and Chennaiah E. Flora of Andhra Pradesh, 1st Edition, Vol I, Scientific publishers: 139, (1997).

Madhavachetty K, Sivaji K and Tulasi RK. Flowering plants of chittoor

district, 1st Edition, Students offset printers: 45, (2008).

Meena KL, Yadav BL, Studies of ethnomedicinal plants by Garasia tribes of sirohi district, Rajasthan, India. Ind J of Nat Prod and Res, 1 (4): 500-506, (2010).

Kokate C K. 20003. Practicals in Pharmacognosy, 1st Edition, Gyan offset

printers: 107-111, (2003).

Goyal RK and Shah BS. Practicals in Pharmacognosy, 5th edition, Nirali Prakashan: 128-55, (2001).