Sedatives And Hypnotics

Question 1

Sleep cycle

Answer 1

Stage 0: awake
EEG shows a activity when eyes are closed and B activity when eyes are open

Stage 1: dozing

Stage 2: unequivocal sleep
Theta waves, little eye movement. Subjects easily arousable. 40-50% of sleep time

Stage 3: deep sleep transition
Theta and delta waves. Not easily arousable

Stage 4: cerebral sleep
Delta activity. Difficult to arouse. Night terrors might occur here.

REM sleep:
EEG has waves of all frequency. Irregular and darting eye movements dreams and nightmares

Question 2

Classification

Answer 2

1. Barbiturates
   Long acting- phenobarbitone
   Short acting- pentobarbitone, butobarbitone
   Ultra short acting- thiopentone, methohexitone
2. Benzodiazepines (BZD)
   Hypnotic- diazepam, flurazepam, nitrazepam
   Antianxiety- diazepam, alprazolam, lorazepam
   Anti convulsant- Diazepam, lorazepam, clonazepam
3. Non BZD hypnotics
   Zolpidem, zopiclone, zaleplon
4. Melatonin receptor agonist
   Ramelteon

5. Misc- 
chloral hydrate (no longer used), anti histamine ( promethazine), opioids etc

Question 3

Sedative and hypnotic definition

Answer 3

Sedative: drug that reduces excitement and calms the person without inducing sleep.

Hypnotic: drug that produces sleep resembling normal sleep
[ hypnotic at lower dose may act as sedative ]

Question 4

MOA of benzodiazepines

Answer 4

They potentiate the inhibitory effects of GABA

Benzodiazepines->
⭕️Bind to specific site (In between alpha and gamma) on GABAa receptor
⭕️Increase in frequency of opening of chloride channels
⭕️Increase in GABA mediated chloride channel
⭕️Increase electro negativity within cell -> Membrane hyper polarisation
⭕️CNS depression

Question 5

Use of benzodiazepines

Answer 5

1) sedation-
⬇️ time required to fall asleep, ⬇️ night awakenings and produces refreshing sleep.
⬆️ time spent in stage 2 and ⬇️ stage 3,4 & REM (action via midbrain reticular formation)
* long term use of BZDs for insomnia is not recommended due to tolerance, dependence and hangover effects*

2) Skeletal muscle relaxant
⬇️ spinal and supraspinal reflexes involved in muscle tone
(Acts on GABA in medulla)
Useful in spinal injuries, tetanus, cerebral palsy

3) Anti anxiety
Some BZD (diazepam, lorazepam) have selective anti anxiety property when given at low dose.
This is due to their action on the limbic system
Tolerance does not develop even on chronic use.

4) Anti convulsant
IV diazepam/ lorazepam are used to control life threatening seizures

5) pre anaesthetic medication and general anaesthesia (adjunct)
Pre anaesthetic- sedative, anxiolytic, amnesiac effects
(Patient will not be anxious -> no HT -> pt fit for surgery [also, pt will not remember the peri operative events later] )
GA- muscle relaxant properties