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Pharmacology MidTerm > Barbiturates > Flashcards

Barbiturates Flashcards

1
Q

What is the mechanism of action of barbiturates?

A

Enhance GABA effects, but bind at a different site than benzodiazepines.
Glutamate receptor inhibition.
Blocks sodium channels at high doses, exerting an anesthetic effect.

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2
Q

Compare barbiturates to benzodiazepines.

A

Barbiturates are stronger and more effective, but less safe.

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3
Q

Why have benzodiazepines replaced barbiturates?

A

Barbiturates:
- Induce rapid tolerance.
- Induce drug-metabolizing enzymes.
- Cause physical dependence.
- More withdrawal symptoms.
- Produce coma at toxic doses.

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4
Q

How are barbiturates classified?

A
  1. Long-acting.
  2. Short-acting.
  3. Ultra-short-acting.
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5
Q

What is the duration of action of long-acting barbiturates?

A

1-2 days.

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6
Q

What is the duration of action of short-acting barbiturates?

A

3-8 hours.

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7
Q

What is the duration of action of ultra-short-acting barbiturates?

A

20 minutes.

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8
Q

List a long-acting barbiturate.

A

Phenobarbital.

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9
Q

List short-acting barbiturates.

A

Pentobarbital.
Secobarbital.
Amobarbital.

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10
Q

List a ultra-short-acting barbiturate.

A

Thiopental.

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11
Q

What are long-acting barbiturates useful for?

A

Treatment of tonic-clonic seizures, status epilepticus, eclampsia, and febrile seizures.

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12
Q

What are short-acting barbiturates useful for?

A

Sedative and hypnotic, but NOT antianxiety.

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13
Q

What are ultra-short-acting barbiturates useful for?

A

Used IV to induce anesthesia.

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14
Q

What effect do barbiturates exert at low doses?

A

Sedation.

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15
Q

What effect do barbiturates exert at higher doses?

A

Hypnosis then anesthesia.

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16
Q

What effect do barbiturates exert at toxic doses?

A

Respiratory depression, coma, and death.

17
Q

What occurs with chronic barbiturate use?

A

Tolerance and stronger dependence compared to benzodiazepines.

18
Q

What do barbiturates lack?

A

Like benzodiazepines, they lack analgesic action.

19
Q

How do barbiturates depress respiration?

A

By suppressing the hypoxic and chemoreceptor response to CO2.

20
Q

What effect do barbiturates exert on enzyme induction?

A

Induction of CYP450, increasing the metabolism of other drugs metabolized by CYP450, decreasing their effect.

21
Q

What are the therapeutic uses of barbiturates?

A
  1. Anesthesia.
  2. Anticonvulsant.
  3. Anxiolytic.
  4. Hypnotic.
22
Q

Which barbiturate is the drug of choice for treating young children with recurrent febrile seizures?

A

Phenobarbital.

23
Q

Why should phenobarbital be used cautiously with adults and children?

A

Suppresses cognitive development in children, and cognitive performance in adults.

24
Q

What are the hypnotic effects of barbiturates?

A

Suppresses REM sleep more than other stages,
Decreases sleep latency, the number of awakenings, and the duration of REM sleep.

25
Q

How are barbiturates absorbed?

A

Orally, and distributed widely throughout the body.

26
Q

Why does thiopental have a short duration of action?

A

Like all barbiturates, it is redistributed from the brain to other tissues, which decreases the duration of action.

27
Q

Why are barbiturates never used for pregnancy?

A

They cross the placenta and depress the fetus’ respiration.

28
Q

How are barbiturates metabolized and excreted?

A

Metabolized in the liver, excreted in the urine.

29
Q

What are the adverse effects of barbiturates?

A

CNS:
- Drowsiness.
- Impaired concentration.
- Mental and physical sluggishness.

Drug hangover: hypnotic doses cause a feeling of tiredness after the patient awakes.

30
Q

Why should antiepileptic women taking oral contraceptives avoid taking barbiturates?

A

Phenobarbital increases the activity of hepatic drug-metabolizing enzymes such as CYP450, decreasing the duration of action of drugs.

31
Q

Why are barbiturates contraindicated for patients with acute intermittent porphyria?

A

Barbiturates increase porphyria synthesis.

32
Q

How do barbiturates increase porphyria synthesis?

A

By inducing ALA synthetase.

33
Q

What effect does increased porphyria synthesis have?

A

CNS dysfunction, coma, and death.

34
Q

What happens when barbiturates are abruptly stopped?

A

Tremors.
Anxiety.
Weakness.
Restlessness.
Nausea.
Vomiting.
Seizures.
Delirium.
Cardiac arrest.

35
Q

What are the signs of barbiturate poisoning?

A
  1. Respiratory depression.
  2. Central cardiovascular depression.
  3. Shock-like condition with shallow, infrequent breathing.
36
Q

How is barbiturate poisoning treated?

A
  1. Hemodialysis.
  2. Artificial respiration and purging the stomach.
  3. Alkalization of the urine by sodium bicarbonate.

Pharmacology MidTerm (8 decks)

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