Lab 3 Introduction Pain an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage Analgesics Drugs used to relief or suppress the pain ID: 515796
Download Presentation The PPT/PDF document "ANALGESIC DRUGS" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
ANALGESIC DRUGS
# Lab
3# Slide2
Introduction
- Pain:
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
- Analgesics :
Drugs used to relief or suppress the pain.Slide3
pain is associated with electrical activity in small diameter primary afferent fibers of peripheral nerves .
These nerves have sensory ending in the peripheral tissues and activated by noxious stimuli of various kinds :
Chemical stimuli
Thermal stimuli
Mechanical stimuliSlide4
Types of afferent sensory nerve fibers :
C- fibers
A
- fibers
Non
-
myelinated
Myelinated
Low conducting velocity
High
conduction velocity
Cause
a dull burning and non-localized pain
Cause a sharp and localized pain Slide5
Nociceptors
A Sensory receptor that
sends signals that cause the perception of
pain
in response to a potentially damaging
stimulus.
These receptors are activated by mechanical, thermal and chemical stimulants.
Provide information about the location, intensity and duration of a noxious stimulus to the body
Nociceptors are connected to primary afferent nerve fibers.Slide6
Pain Mediators
pain mediators include :
bradykinin
,
leukotriene
, substance P, histamine, Ach, 5-HT and prostaglandins
they increase the sensitivity of the nerve ending to other pain mediators
Slide7
Pain Mediators
Mechanism of action of the
paim
mediators to cause pain :
Direct :
stimulate of the nerve ending directly via
nocieceptors
.
Indirect :
increase the sensitivity of nerve ending to other pain mediators.Slide8
Analgesics are divided into
Narcortic
analgesics
(
opioid
analgesics )
e.g.
Morphine
Non- narcotic analgesics
( non-
opioid
analgesics )
( non- steroidal
anti-inflammatory drugs )
NSAIDs
e.g.
AspirinSlide9
Opioid analgesics
Opioid include natural (
Morphine
),
semisynthetic
(
Heroin
) and synthetic (
Fentanyl
).
They reduce moderate to severe pain without loss of consciousness.
They act by binding to specific receptors located primarily in the brain and spinal cord.Slide10
Opioid analgesics
The major classes of
opioid
receptors are(
μ
,
κ
,
δ
) mu, delta and kappa.
Each receptor type has subtypes: mu1, mu2, delta1, delta2, kappa1, kappa2 and kappa3.
Most of the currently available
opioid
analgesics act primarily at the mu receptor. Slide11
Mechansim
of action :
All
opioid
recptors
are linked through G-
proiten
by inhibition of
adenylate
cyclase
i.e
facilitate opening of K channels (
causing
hyperpolarization
) and inhibit opening of Ca channels ( inhibiting transmitters release )
They stimulate the release of endogenous
opiod
peptide (
endorphins and
enkephalins
) which cause
decresing
in release of pain mediators.Slide12
Side effects:
Dependency
and
tolerance
Nausea and
constipation
CNS:
drowsiness, lightheadedness, euphoria or
dysphoria
, or confusion.
Urinary retention
Respiratory depression
, particularly in elderly or debilitated patients
Miosis
(
constriction of the pupil
)Slide13
Non opioid
analgesics (
NSAIDs
)
Aspirin and other NSAIDs are useful for the treatment of pain from injury (
mild to moderate
)
Examples for NSAIDs :
Cox (
cyclooxygenase
) non selective :
Aspirin, Ibuprofen,
Diclofenac
…etc
Cox2 selective :
Celecoxib
and
Rofecoxib.Slide14
Phospholipids
Phospholipase
A
2
Arachidonic Acid
Prostaglandins
Thromboxanes
Prostacyclin
COX
Leukotrienes
LipoxygenaseSlide15
LAB WORK
Objective :
To show the analgesic effects of different analgesics using different methods.
Writhing test.
Hot plate method.Slide16
Writhing test
Principle
:
Pain is induced by injection of noxious chemical as Acetic acid 0.1% at volume 0.3 ml.
Writhing means stretching behavior of the abdominal and at least one hind limb.Slide17
Procedure:
1.First inject the mouse with acetic acid and calculate the number of writhing/20 minutes and this will be control test.
2.Inject the second animal with aspirin and inject the third one with morphine.
3.After 5 minutes inject the animals with acetic acid then calculate the number of writhing/20 minutes.Slide18
Procedure:
4.Compare the number of writhing for each drug and comment on the results (a drug has more number of writhing >>> more potency as analgesic
. Slide19
Drug
No. of writhing/20 minutes
Control
Acetic cid
Test 1
Morphine acetic acid
Test 2
Aspirin acetic acid
5 min’s
5 min’sSlide20
Hot plate method
principle:
The paws of the mouse are very sensitive to heat at temperature which are not damaging the skin .
At temperature of 55 C
the mouse will jump and licking the paws.
The time till these response occur is calculated and is prolonged after administration of analgesics.
Slide21
Procedure:
Put the mouse on the hot plate and record the time taken in order to jump or licking the fore paws.
Record the time in seconds this is the control time.
Weight the animal and calculate the dose of Morphine and Aspirin
At 5 min’s interval ( for 30 min’s ) place the animal on the hot plate and record the time to see the response .
Compare the time need to see the response the drug with longer time is more potent as analgesic.Slide22
Drug
Time interval
zero
5
10
15
20
25
30
Morphine
aspirinSlide23
Conc (g%)
Dose mg/Kg
Morphine
0.2%
20
aspirin
3%
300