Sedative & Hypnotic Drugs
Sedative: Drugs that reduce anxiety, excitement, and exert a calming effect without affecting mental functions are called sedative
Hypnotics: Drugs
that produce hypnosis is called hypnotics.
Hypnosis: It is a sub
conscious condition in which the objective manifestations of the mind are more
or less inactive, accompanied by abnormal sensitivity.
Classifications of hypnotics: Hypnotics are mainly two types.
1. Barbiturate
hypnotics
2. Non- barbiturate hypnotics
Barbiturate hypnotics: They are sub divided into four classes:
a) Long acting barbiturates (8-12 hours)
For example: Barbitone, Phenobarbitone
b) Intermediate acting barbiturates (6-8 hours)
For example: Allo- barbitone, Amilo barbitone
c) Short acting barbiturates (3-6 hours)
For example: Pento barbitone, Seco- barbitone
d) Ultra short acting barbiturates (0.5-3 hours)
For example: Thiopental sodium
Non barbiturate hypnotics: They are sub divided into two classes:
a) Organic group: Benzodiazepines (Diazepam,
Oxazepam, Nitrazepam)
Aldehyde derivatives (Paraldehyde)
Alcohol (Chloral hydrate)
Carbamate derivatives (Ethinamate)
Miscellaneous (Anti- histamines, scopolamine)
b) Inorganic group: Sodium Bromide (NaBr),
Potassium Bromide (KBr), Ammonium Bromide (NH4Br)
Clinical use of sedatives and hypnotics:
To relief
anxiety and depression
For hypnosis
Sedation and
amnesia before and after surgical procedure
In the
treatment of epilepsy and seizure
Pre
medication prior to anaesthesia
For muscle
relaxation
Diagnosis
aids or for the treatment in psychiatry
As a component of balanced anaesthesia
BARBITURATES
Barbiturates: Barbiturates
are the derivatives of barbituric acid.
Mechanism of action of barbiturates: Mechanism of action of barbiturates is schematically shown below:
Barbiturates + GABA ।Activation of GABA Receptor । Opening of Cl- channel ।Hypotension of cells ।CNS depression
Pharmacological action of barbiturates:
1) On CNS:
Mild degree of sedation to general anesthesia, anti- convulsant effect,
respiratory depression
2) On CVS:
Hypotension, decrease heart rate
3) On kidney:
Increase ADH secretion, Depress GFR.
4) On GIT:
Constipation may occur in prolonged use.
5) On liver:
Stimulate glucoronyl transferase enzyme secretion
6) On eye: Toxic dose causes myosis.
Therapeutic use of barbiturates:
1) Used as
sedative & hypnotics
2) In
narco-analysis and narcolepsy.
3) As
anti-convulsant: Tetanus, Epilepsy.
4) During
surgical anesthesia
5) Sometimes
used to antagonize unwanted CNS stimulant drug.
6) Cholestasis
7) Help in diagnosis & therapeutic use for
psychiatric patient.
Adverse
effect of barbiturates:
1) At hypnotic
dose, drowsiness may contain for long time
2) Nausea,
vomiting, diarrhea
3) Paradoxical
excitement: In some persons, barbiturates repeatedly produce excitement rather
than depression
4)
Hypersensitivity: Rash, localized swelling at eye, leaps etc.
5)
Respiration: In hypnotic dose, the effect of respiratory system is minor. But
serious respiratory depression may occur sometimes.
6) Tolerance & dependence: Cellular and
pharmacokinetic dependence may occur.
Barbiturate poisoning: 20%-70% of poisoning occurs due to barbiturates. It occurs due to
suicidal or accidental.
Fatal dose is ten times of clinically used dose.
Symptoms of barbiturate poisoning:
1) On CNS:
Drowsiness, respiratory depression, slow breathing, coma.
2) On CVS:
Hypotension, dehydration, shock.
3) Lungs:
Pulmonary edema, bronchopneumonia
4) Kidney:
Cerebral depression, renal failure.
5) Eye: Miosis
6) Skin:
Lesion
7) Death from: Respiratory depression
Treatment of barbiturate poisoning:
1) Removal of
unabsorbed drug by stomach wash.
2) Artificial
respiration and oxygen inhalation
3) Use
activated charcoal as specific antidote
4)
Hemodialysis
5) Forced
alkaline diuresis
6) Use cardio
tonic agent: for example, dopamine
7) Use antibiotic to prevent pulmonary infection
Benzodiazepines
Benzodiazepines are the drugs which have
sedative, hypnotic, anti- anxiety, anti-convulsant and muscle relaxant
properties. They are more popular than barbiturates.
Classification of benzodiazepines:
Based on duration of action, benzodiazepines are
three types:
a) Short acting ( Half life is less than 5 hours)
For example: Triazolam, Midazolam
b) Intermediate acting (Half life is within 8-15
hours)
For example: Lorazepam , Oxazepam
c) Long acting (Half life is upto 200 hours)
For example: Diazepam, Nitrazepam, Clonazepam,
Flurazepam
Mechanism of action of Benzodiazepines:
Mechanism of action of Benzodiazepines is
schematically shown below:
Benzodiazepines
।
Binds with GABA receptor in brain
।
Enhance GABA activity
।
Opening Cl- channels
।
Hyperpolarization of cells
।
CNS depression
Pharmacological
action of benzodiazepines:
1) Show
anxiolytic and tensiolytic effect.
2) Sedative
and hypnotic effect
3) Anti-
convulsant effect
4) Skeletal
muscle relaxant effect
5)
Neuromuscular blockage
6) Coronary vasodilation
Therapeutic use of Benzodiazepines:
1) Treatment
of anxiety
2) As sedative
and hypnotic
3) Used as
skeletal muscle relaxant
4) Used as pre
anesthetic medication
5) Used as
anticonvulsant
6) For general
anesthesia
7) Management
of alcohol withdrawal syndrome
8) In case of endoscopy and cardioversion
Antidote of Diazepam: ‘Flumazenil’ is very active antagonist of Benzodiazepine
Adverse effect of Benzodiazepine:
1) Dry mouth
2) Light
headache
3) Lassitude
4) Ataxia
5) Drowsiness
6) Ataxia
7) Confusion
8) Acute
overdose causes prolong sleep
9) Tolerance and dependency
Advantage of Benzodiazepine over Barbiturates:
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