CNS Depressants Lab # 2

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

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

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

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

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

Sedative – hypnotics: Classification

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

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)

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

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

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)

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