Barbiturates are CNS depressants that were historically used as sedatives and hypnotics. They are synthesized from urea and malonic acid. Barbiturates work by enhancing the effects of the neurotransmitter GABA, causing neuronal hyperpolarization. They can cause sedation, hypnosis, narcosis, general anesthesia, and even death depending on dosage. Barbiturates are classified based on their duration of action and chemical structure. While formerly widely used, barbiturates have been replaced by safer alternatives due to risks of overdose, tolerance, and drug interactions.

1. Barbiturates
Presented By
Rasel mahbub
&
Ananta sutradhar

2. CNS depressants
 CNS depressants are substances that can slow brain activity by
selectively depressing neuronal activity in posterior
hypothalamus.
 Barbiturates are derivatives which is synthesized by urea &
malonic acid.
Malonic acid
Barbituric acid
Barbiturates
 It was first prepare by a german scientist Adlof Von Baeyer in
1864,combining urea from animal & malonic acid from apples.

3.  It was used as sleeping aid(hypnotic only) from 1903-
1950.Since 1950 they have been popular drug in the
UK,these were previously popular drug of abuse.
 It was estimated that 27000 peoples died from
barbiturates overdose in the UK between 1959-1974.

4. Synthesis

5. Progressive grade of CNS
depressant
Sedation
Hypnosis
Narcosis
General anaesthesia
Coma
Death

6. Classification
according to duration of action
.Ultra-short acting Properties
1.Theopental act within second
2.Hexo-barbitone D/A:30 min
Main use:
as I/V anaesthesia

7. Short acting Properties
1.Pento-barbitone D/A:2 hours
2.Quino-barbitone Main use:
as sedative

8.  Intermediate acting Properties
 1.Amilo-barbitone D/A:3-6 hour
 2.Allo-barbitone Main use
 3.Buto-barbitone Hypnotic
 4.Vin-barbitone

9. A)Long acting Properties
1.Barbitone D/O:>6 hour
2.Pheno-barbitone Main use:
3.Mepho-barbitone Anticonvulsant
4.Apo-barbitone

10. According to chemical structure
 1.Oxybarbiturate
 (If oxygen is present)
 2.Thiobarbiturate
 (If oxygen is replaced by sulpher)

11. Mechanism Of Action
 Barbiturates are general depressants of all cell of the
body,acting as a cellular histotoxic agent.But the cell of the
CNS are more sensitive to barbiturate action.
 1.Barbiturate induce sleep by selectively depressing RAS in
the brain stem.
 2.Barbiturate selectively depress neuronal activity in
posterior hypothalamus,amygdaloid nucleus& limbic
structure (CNS depression)
 3.Barbiturates depress monosynptic pathway of spinal
cord(anticanvulsion)
 4.Barbiturates have also GABA like activity or enhance
GABA activity.

12. Mechanism of action
Barbiturate+GABA
Activation of GABA receptor
Opening of chloride channel
Increase the duration of GABA gated channel opening
Hyperpolarisation of cells
Depression of CNS

13. Pharmacological action of
Barbiturates
 A.On CNS
 1.Mild degree of sedation to general anaesthesia.
 2.Anticonvulsant effect.
 3.Respiratory centre depression
 B.On CVS
 1.Hypotension
 2.Decrease heart rate
 3.Circulatory collapse

14.  C.On liver
 1.Enzyme induction,so increase metabolism of itself &
other drugs.
 2.Stimulate glucoronyl transferase.
 D.On kidney
 1.Antidiuretic effect (increase ADH)
 2.Decrease urinary output by depressing GFR

15.  E.On eye
 1.No effect (normal dose)
 2.Miosis ( toxic effect)
 F.On GIT
 1.Constipation (on prolong use)

16. Structure

17. Indication
1.As anticonvulsant
tetanus
eclampasia,
epilesy
cerebral haemorrhage
convulsant drug poisoning
during surgical anaesthesia
2.As sedative & hypnotic
3.Intravenous anaesthesia
4.Hyperbilurobinaemia & kernicterous

18.  5.Haemolytic jaundice
 6.Cholestasis
 7.In narco analysis &narcopathy
 8.Identifying the dominant cerebral haemisphere for
speech prior to neuro surgery
 9.Kernicterus in children

19. Contraindication
 1.Pulmonary insufficiency,pulmonary emphysema
 2.In idiosyncratic patient
 3.Acute intermittent pophyria
 4.In impaired renal function
 5.In hepatic failure
 6.Ptient with suicidal tendency
 7.CCF & hypovolmic shock

20. Adverse effect of Barbiturates
 1.Pain;Localized or diffuse myalgic,neuralgic or
arthritic pain especially in psychoneurotic patient.
 2.Allergic skin lessions
 3.After effects
 drowsiness
 Hangover effect
 Over excitement
 Night mares & night terrors
 weakness & lethargy

21.  4.Drug automatism
 5.Enzyme induction (so tolerance develops rapidly)
 6.Idiosyncratic reaction:barbiturates precipitate
attacks of acute porphyria in sussceptible individual.

22. Doses of barbiturates
 The typical dose of phenobarbital use as
anticonvulsant,,
 For adult:50-100 mg,2/3 times per day
 For newborn:2-4 mg per kilogram of body weight per
day
 For infant:5-8 mg per kilogram pf body weight
 For sedation before surgery 100-200 mg,one hour
before surgery

23. Commercial brand name available
in BD
 Brand Name Manufacturer
 Barbit Incepta pharma
 Genesia DS Square
 Nelepsin Beximco
 Parotin ACI pharma

24.  Sedative:Drugs that reduce anxiety,excitement & exert
calming effect without effecting mental function.It is
usually lower or normal dose,not higher dose.
 Hypnotic:Drugs those cause of sleep are called
hypnotic. Usually higher dose not normal or lower
dose
 Sedative given day time hour,they makes patient
drowsy not sleep
 Hypnotics are given at night of sleep