Anti-anxiety/ Hypnotic (Barbiturates).

Question 1

Classification:

Answer 1

1- Barbiturates.

2- Binzodiazepines.

3- Other anxiolytics.

4- Other hypnotics.

Question 2

Barbiturates:

(Classification)..

Answer 2

1- Long duration of action:
(Phenobarbital).

2- Short duration of action:
(Penobarbital, Secobarbital, Amobarbital).

3- Ultra-short duration of action:
(Thiopental).

Question 3

Site of action of BARBITURATES:

Answer 3

• Neurones and synapses of mesencephalic reticular activating system (RAS).

Question 4

Mechanism of action of BARBITURATES:

Answer 4

Stimulate the release of GABA via:

• Increase the duration of chloride (GABA-gated) opening channels.

Question 5

Pharmacokinetics of BARBITURATES:

Answer 5

1- Absorption:
- will absorbed.

2- Distribution:
(Thiopental) is:
- highly lipid soluble.
- cross BBB rapidly.
- redistributed in the less vascular tissue.
- Very rapid onset of action (within 30sec.).

3- Excretion:
(Phenobarbital) is:
- excreted unchanged in urine.
- can increase its excretion by alkalinization of urine.

Question 6

Effects of BARBITURATES:

(CNS)..

Answer 6

Depression of CNS

• Low dose: Sedation.
• High dose: Hypnosis

Question 7

Effects of BARBITURATES:

(Respiratory)..

Answer 7

• Respiratory depression*
• Lethal dose: suppress the Hypoxic & Chemoreceptor response to CO2.
• Over dose: Respiratory depression and Death.

Question 8

Effects of BARBITURATES:

(CVS)..

Answer 8

• High dose: Hypotension (due to suppresstion ganglionic transmission), and suppress VMC.

Question 9

Effects of BARBITURATES:

(Liver)..

Answer 9

• Enzyme inducers.

- Decrease effects of many drugs.

Question 10

Therapeutic uses of BARBITURATES:

Answer 10

1- Anesthesia (Thiopental).

2- Sedative/Hypnotic.

3- Anticonvulsant (Phenobarbital): tonic-clonic seizures, status epilepticus, & eclampsia.

• Phenobarbital the drug of choice for treatment of young children with recurrent febrile seizures.
• Phenobarbital can depress cognitive performance in children.

Question 11

Adverse effects of BARBITURATES:

Answer 11

CNS:
(Drowsiness & mental confusion).

Hangover: in hypnotic doses..
(الشعور بالتعب بعد الإستيقاظ)

Inducing AminoLevulinic Acid (ALA) synthetase → increase porphyrin synthesis (contraindication in patients with acute intermittent porphyria).

Question 12

Contraindications of BARBITURATES:

Answer 12

1- Pregnancy: depress fetus.

2- Acute intermittent porphyria.

Question 13

Drugs interactions of BARBITURATES:

Answer 13

Reduce effects of many drugs such as:

Phenytoin, contraceptive, many anticoagulants.