cns depressants lab # 2. objectives to demonstrate the effect of different types of cns depressants...
TRANSCRIPT
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 )receptor.2
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