Download Classroom Expectations

CNS Depressants
Lab # 2
Objectives
•
To demonstrate the effect of different types
of CNS depressants as :
- General anaesthetics
- Hypnotics ‫المنومات‬
- Sedatives ‫المسكنات‬
- tranquilizers ‫المهدئات‬
To learn how to distinguish between their
signs if they are given as unknown drugs.
Introduction
• CNS depressants are drugs that can be used to
slow down brain activity or function .
• There are numerous CNS depressants; most
act on the brain by affecting the
neurotransmitter gamma-aminobutyric acid
(GABA).
• GABA works by decreasing brain activity.
• CNS depressants have ability to increase
GABA activity that they produce a drowsy or
calming effect that is beneficial to those
suffering from anxiety or sleep disorders.
General Anaesthetics
• They are drugs which produce reversible loss
of consciousness ‫ الوعى‬.
• Mechanism of action :
- They alter chloride channel opening cause
hyperpolarization so they decrease firing.
- They facilitate the inhibitory effects of GABA
.
Stages Of Anesthesia
I.
Stage of analgesia: decrease feeling of pain
but the patient is still conscious.
II.
Stage of excitement: delirium , respiration is
irregular and the consciousness is lost but the
feeling of severe pain is present.
III. Stage of surgical anesthesia: regular
respiration, relaxation of the skeletal muscles
and the feeling of surgery is lost.
The Target Stage
Stages Of Anesthesia
IV. Stage of medullary depression: severe
depression in vasomotor center in the
medulla and respiratory center. Without full
circulatory and respiratory support the result
is death.
Classification of General Anesthetics
•
There are two types of General Anesthetics
agents:
1) Inhaled Anesthetics
2) Intravenous Anesthetics
A- Inhaled agents:
1) Volatile liquid:
e.g. Halothane, Isoflurane, Enflurane, Desflurane,
Sevoflurane and Methoxyflurane.
2) Gas:
e.g. Nitrous oxide .
B- IV agents:
Ultra short acting Barbiturates ( e.g. Thiopental),
Ketamine, Propofol, Midazolam
(Benzodiazepines) and Fentanyl ( Opioid).
Hypnotics
• They are drugs that induce sleep in case of
insomnia. e.g. Barbiturates and
Benzodiazepines.
• Barbiturates & Benzodiazepines act by
enhance the actions of GABA.
Classification of Barbiturates
•
Based on the duration of action
1. Ultrashort acting: ( 15 minutes) e.g. Thiopental.
2. Short acting: ( 2-4 hours) e.g. Pentobarbital .
3. Intermediate acting: (4-6 hours) e.g. Amobarbital.
4. Long acting: ( 6-8 hours): e.g. Phenobarbital.
Sedatives
• Drug that cause sedation and to calm the
patient down without inducing sleep.
• When the dose increased they will induce
sleep.
• E.g. Chloral Hydrate
• Trichloroethanol is the active metabolite of
chloral hydrate .
• Trichloroacetic acid is the toxic metabolite .
Tranquilizers
• They are drugs which used to relieve mental
anxiety and stress.
• E.g. chlorpromazine (CPZ).
• Work by blocking dopamine (D 2 )receptor.
Righting reflex
• Test the ability of the mice to assume optimal
position .
• When it lost: (-ve)
• With Phenobarbital righting reflex –ve
• With Chloral hydrate: at sedative dose the
righting reflex is +ve , when the dose repeated it
will induce sleep and the righting reflex will be –ve.
• With chlorpromazine: righting reflex is +ve and
still +ve even the dose is repeated .
Chlorpromazine (CPZ)
• After injection of CPZ we can observe signs
as:
• Ataxic gait: loss of muscle coordination .
• Catalepsy : rigid body
• Grasping test (CPZ):
When you trying to put the mice on the cord, the
mice will fall down
Calculate the dose
Type
Example
Conc (g%) Dose (mg/kg)
Hypnotic
Phenobarbital
2%
200
Sedative
Chloral Hydrate
3%
150
Tranquilizer
Chlorpromazine
0.2%
40
Injection volume =
Dose (mg/Kg) x Body weight in Grams
Conc g% x 10000
= xxxxx ml