Screening of
Antipyretic
Drugs
Presenter:-
Dr Arun Singh
3rd Year Resident Doctor
Department of Pharmacology
SMS Medical College,Jaipur

Outliner's
Introduction
Antipyretic Drugs
Screening Models
Antipyretic Activity-yeast Induced Pyrexia Method
Antipyretic activity of Bauhinia Racemose Lam in Rat
Antipyretic activity of Gracilaria Corticataj
Antipyretic activity in Rabbits

Introduction
• An antipyretic is a type of medication that will prevent or reduce
fever by lowering body temperature from a raised state.
• They will not affect normal body temperature if the patient does not
have a fever.
• Generally, most non-steroidal anti-inflammatory drugs (NSAIDs)
work by inhibiting prostaglandin synthetase within the hypothalamus.
• Fever, or pyrexia, occurs when the body reaches a temperature above
what is considered "average".
• Bear in mind, however, that this "average" temperature can vary from
person to person within certain parameters.

• It is generally accepted fever exists at a temperature above 37 degrees
Celsius when the thermometer is placed under the armpit, or over 37.5
degrees Celsius when measured orally or rectally.
• Fever usually results from microbes such as bacteria or viruses
triggering the body's defense mechanisms.
• Antipyretics (literally "against the fire") are drugs that reduce fever.

Antipyretic Drugs
• The drugs which lowers the elevated body temperature to the
normal .
• Drugs used are :
1. Aspirin (Non-selective COX Inhibitor)
2. Paracetamol (Inhibitor of PG’s synthesis)

Mechanism of action
• Antipyretic drugs resets the thermostat toward normal and
rapidly lowers the body temp of febrile patients by increasing
heat dissipation as a result of peripheral vasodilation and
sweating.
• Inactivation of COX enzyme.

Screening models
Brewer’s yeast
suspension
method
Antipyretic
activity in
rabbits
Antipyretic
activity in rats

Antipyretic activity-yeast induced pyrexia method
• The body temperature of each albino Wistar rats was recorded by
measuring rectal temperature at predetermined intervals.
• Albino wistar rats are grouped into four containing six in each
group.
• The rats are trained to remain quiet in a restraint cage.
• A thermistor probe is inserted 3 to 4 cm into the rectum and
fastened to the tail by adhesive tape.
• Temperature is recorded on a thermometer.

• After measuring the basal rectal temperature, animals are given
subcutaneous injections of 10 ml/kg of 15% w/v yeast suspended in a
0.5% w/v methylcellulose solution.
• At the 19th hr after yeast injection the rectal temperature of the rats
were recorded.
• After yeast injection the test drug is administered with dose 250, 500
mg/kg to III & IV group animals.
• Propylene glycol at dose of 5ml/kg was injected to the control group.
• The II group of rats received the standard drug paracetamol at the dose
of 150 mg/kg at the 19th hr after yeast injection.

• Subcutaneous injection of yeast suspension markedly increased the
rectal temperature 19th hr after its administration.
• Rectal temperature of all the rats was recorded again on the 20th, 21st
and 22nd hr after yeast injection.
Group Category Drug Solution
Group-I Control Propylene glycol (5ml)
Group-II Standard drug Paracetamol (150mg)
Group-III Methanolic extract of Tephrosia purpurea
(250mg)
Group-IV Methanolic extract of Tephrosia purpurea
(500mg)

Evaluation
• A decrease of body temperature for at least 0.5°C
for more than 30 min as compared with the
temperature value before administration of the
test compound is regarded as positive effect.

Antipyretic activity of Bauhinia Racemose Lam in
rat
• The plant Bauhinia racemose Lam belongs to the
“Caesalpiniaceae” Family.
• It is popularly known as “Apta” in Marathi, “Kanchnal” in Hindi.
• Dhar et al, (1968) reported the antipyretic activity in mice from
the hydro alcoholic extracts of Bauhinia racemose.
• The plant Bauhinia racemose Lam. Belongs to the
“Caesalpiniaceae” Family. It is popularly known as “Apta” in
Marathi, “Kanchnal” in Hindi.

Dhar et al, (1968) reported the antipyretic activity in mice from the hydro alcoholic
extracts of Bauhinia racemose.
Thirty-six healthy Wistar Albino rats of 200- 250gms were divided into six groups of six
animals each, with 50% sex ratio.
The initial rectal temperature of each animal was recorded by digital thermometer and its
hourly variation was noted for 3 and their average was recorded
The pyrexia was induced by injecting a suspension of 15% of brewer’s yeast and 2% gum
acacia in normal saline subcutaneously below the nape of neck in the volume of
1ml/100gm of animal weight.

The aqueous extract was given orally to group 1& 2 of 100,200mgkg
The alcoholic extract was given orally to group 3& 4 of 100,200mgkg.
The 5 group is given with paracetamol of 100,200mgkg/
Sixth group is given with saline sol of 0.5 ml serve as negative control.
Rectal temperature was recorded at 1,2&3 hour.
The difference in temperature between 0 hour and at the end of 3 hr it is compared.

Aqueous and alcoholic extracts of Bauhinia racemose Lam. produced significant
antipyretic activity in rats, which was induced by brewer’s yeast.
The temperature was brought back to normal after 4 hrs of post administration of
extracts.
The aqueous extract @200mg/kg body weight and alcoholic extract @100mg/kg and
200mg/kg body weight was found to have significant effect and was found significant
at 5% level of significance.

Antipyretic activity of Gracilaria Corticataj
Gracilaria corticata J.Agardh is red seaweed belonging to Rhodophyceae member
shows much attention in the present study for antipyretic activity.
Gracilaria corticata J.Agardh were collected from Hare island, Thoothukudi in the
southeast coast of Tamil Nadu.
The shade dried samples were grounded to fine powder & 3g powdered sample
was packed in Soxhlet apparatus and extracted with methanol for 8 hrs.
The excess amount of methanol was evaporated, and fine methanol crude
powder was prepared and stored in the refrigerator for the antipyretic activity.

Swiss albino rats were weighing (150-240 gm) and male albino rats
(15-18 gm) were used.
The animals were housed in the departmental animal house under
standard conditions (26±2°C and relative humidity 30-35%) in 12 hours
light and 12 hours dark cycle respectively for 1 week before the
experiment.

The experimental treatment was carried out as;
Group I: Control group animals Normal saline 5ml/kg
Group II: Animals were treated with Paracetamol (10mg/kg)
Group III: Animals were administered with 200mg/kg methanol extract
Group IV: Animals were administered with 400mg/kg methanol extract

Results
• Antipyretic activity of methanol crude extract of
Gracilaria corticata
J. Ag. was studied by determining the effect on yeast-
induced pyrexia in albino rats.
• The result expressed that methanol extract of different
doses caused lowering of the body temperature up to
4h following its administration.
• The effect of methanol extract on yeast-induced
pyrexia showed that the rectal temperature was
markedly elevated to 41.7°C, after 18h the
subcutaneous injection of yeast suspension decreased
to 40.7°C within 1h of 200mg/kg methanol extract of
Gracilaria corticata J. Ag.

• Treatment followed by 39.6°C at 2h and further
reduced to 38.2°C at 4h showing a considerable
decrease in compared to paracetamol.
• 400mg/kg methanol extract also showed the
decreased in temperature from 41.4°C to 39.6°C
after 1h of treating with the administration of the
methanol crude extract of Gracilaria corticata J. Ag.
• When the time was increased up to 4hr,the results
were observed significant reduced temperature to
37.2°C.
• Both 200 and 400mg/kg marked antipyretic activity
detected were significantly different than the
controls (p<0.05).

Generally, for all concentration of
methanol crude extract of Gracilaria
Corticata J. Ag. Showed marked
antipyretic activities, hence, 400mg/kg
methanol extract was highly effective
than 200mg/kg.
This result revealed that the
methanol extract of
Gracilaria Corticata
J. Ag. Have detectable
antipyretic activity as
compared with standard
paracetamol.

Antipyretic activity in rabbits
Purpose and Rationale:
 Lipopolysaccharides from Gram-
negative bacteria ,e.g., E.coli, induce
fever in rabbits after i.v. injection.
 Body weight of 150 g are used.
 Initial temperature is noted down.
 Fevered by injection of 10mlkg
Brewer's yeast suspension by s.c. .
 The room temperature is kept at 22-24c.̊

The animals are receiving the test and standard drug by oral
The rectal temperature are recorded in 30-, 60-, 120- and 180-min post dosing
Evaluation :
• The difference between the actual values and the starting values are registered for each time
interval.
• The maximum reduction in rectal temperature in comparison to the control group is calculated.

• Results are compared with effect of the standard drug ,e.g.,
aminophenazone 100 mg/kg.