screening of analgesics & antipyretic
TRANSCRIPT
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
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