1. CNS Depressants
Lab # 2

2. CNS Depressants: Classification
They are classified according to their pharmacological action into:
1- Sedative – hypnotics
2- Tranquillizers
3- Anaesthetics

3. I- Sedative - hypnotics
Definitions
Sedatives:
Drugs which calm the patient & cause sedation and in large doses cause sleep
Hypnotics:
Drugs which induce sleep that resembles the natural sleep
Ex. Barbiturates

4. Sleep Definition: Sleep cycle:
Physiological depression of consciousness
Sleep cycle:
Starts with latency period → NREM → REM → cycles of NREM alternate with REM (about 4 cycles)
NREM
REM
- Non rapid eye movement
- Lasts for 90 min.
- Thinking
- Rapid eye movement
- Lasts for 20 min.
- Dreaming

5. II- Tranquillizers Definition:
Tranquillizers are drugs which relief mental anxiety & stress without affecting the consciousness
Ex. Chlorpromazine (CPZ)
MOA: D2 receptor antagonist

6. III- Anaesthetics Definition: MOA:
Drugs which cause unconsciousness & generalized loss of pain sensation, thus allow surgical procedures to be carried out
Ex. thiopental (IV) , halothane (inhalation)
MOA:
Interfering with propagation of nerve impulses by interfering with electrolytes movement through the cell membrane

7. Sedative – hypnotics: Classification

8. 1- Barbiturates MOA: Classification:
They have GABA like action → ↑ opening time of chloride channels → ↑conductance of chloride ions → hyperpolarization
Classification:
1-Long-acting
2-Intermediate-acting
3-Short acting
4-Ultrashort acting

9. 2- Benzodiazepines MOA: Ex.
Bind non-selectively to BZD receptors omega1 (GABA-dependant) & omega2.
chloride dependant →hyperpolarization
‡ omega1 → ‡ GABA receptors
Gi protein → ↓cAMP → relaxation
Ex.
- Diazepam (sedative)
- Triazolam (hypnotic)

10. 3- Non-barbiturate Non-BZD
1- 5-HT agonist e.g. buspirone (5-HTA1)
2- Chloral hydrate (prodrug) converted to trichloroethanol
3- Antihistamine e.g. diphenhydramine
4- Paraldehyde
5- Promethazine

11. General signs for CNS depressants
1- ↓ vitality
2- ↓ excitability
3- ↓ HR & RR

12. Specific signs of sedative-hypnotic
Drugs: thiopental, phenobarbital & chloral hydrate
Sings:
1- Staggering gait
2- Sleeping posture
3- Loss of righting reflex (onset time)
4- ↓ Touch & pain reflexes (lost with thiopental)

13. Specific signs for CBZ Signs: 1- No loss of righting reflex
2- Creeping gait
3- Abdomen touches the ground
4- State of catalepsy (loss of muscles control)→ onset time
5- ↓ Touch & pain reflexes