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Y2 LCRS 1 - Pharmacology and Therapeutics > Anxiolytics and Hypnotics > Flashcards

Anxiolytics and Hypnotics Flashcards

1
Q

What are the four main proteins that make up the GABA-A receptor?

A

GABA receptor protein
Benzodiazepine receptor protein
Barbiturate receptor protein
Chloride channel protein

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2
Q

What protein links the GABA receptor proteins and the benzodiazepine receptor protein?

A

GABA modulin

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3
Q

Describe the normal physiological action of GABA.

A

GABA binds to the GABA receptor protein
GABA modulin links the GABA receptor protein and the benzodiazepine receptor protein
This results in opening of the chloride ion channel

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4
Q

Name a competitive antagonist of the GABA receptor protein.

A

Biciculline

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5
Q

Name a competitive antagonist of the benzodiazepine receptor protein.

A

Flumazenil

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6
Q

What are the two main effects of benzodiazepines that facilitate GABA neurotransmission?

A

They facilitate the GABA-mediated opening of the chloride channel
They facilitate the binding of GABA to its receptor protein (increase theaffinity of GABA to the GABA binding site) – this is reciprocated

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7
Q

What are the three main effects of barbiturates that facilitate GABA neurotransmission?

A

They enhance the normal physiological action of GABA
They enhance GABA binding to the GABA receptor protein (NOT reciprocated)
At higher concentrations, barbiturates can have a direct action on the chloride channel

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8
Q

What is the key difference in the mechanism of action of barbiturates and benzodiazepines?

A

Benzodiazepines – increase the frequency of chloride channel opening
Barbiturates – increase the duration of chloride channel opening

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9
Q

What is the relative difference in selectivity between barbiturates and benzodiazepines?

A

Barbiturates are LESS selective
This may explain why barbiturates induce surgical anaesthesia and why barbiturates are less safe than benzodiazepines
NOTE: barbiturates also reduce excitatory transmission

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10
Q

Name a barbiturate that is used as an anaesthetic.

A

Thiopentone

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11
Q

Name three barbiturates and benzodiazepines that are used as anti-convulsants.

A

Diazepam
Clonazepam
Phenobarbital

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12
Q

Name a benzodiazepine that is used as an anti-spastic.

A

Diazepam

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13
Q

What are two other clinical uses of benzodiazepines and barbiturates?

A

Anxiolytics

Hypnotics

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14
Q

Define anxiolytic.

A

Remove anxiety without impairing mental or physical activity

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15
Q

Define sedative.

A

Reduce mental and physical activity without producing loss of consciousness

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16
Q

Define hypnotic.

A

Induces sleep

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17
Q

What structure is common to all barbiturates?

A

Six-membered ring (4 carbons and 2 nitrogens)

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18
Q

Barbiturates have been largely superseded by benzodiazepines. Which barbiturate is still used relatively commonly?

A

Amobarbital

19
Q

What is the half-life of this drug?

A

20-25 hours

20
Q

What are the unwanted effects of barbiturates?

A

Low safety margin (overdose can be lethal)
Alters natural sleep (reduced REM)
Enzyme inducers
Potentiate the action of other CNS depressants (e.g. alcohol)
Tolerance
Dependence

21
Q

What structure is common to all benzodiazepines?

A

They are tricyclic

22
Q

What are the three key benzodiazepines?

A

Diazepam
Oxazepam
Temazepam

23
Q

What is the difference between all the benzodiazepines that are in clinical use?

A

Their pharmacokinetics

24
Q

Describe the administration of benzodiazepines.

A

Well absorbed per orally

Peak plasma concentration after about 1 hour

25
Q

When would you give IV benzodiazepines?

A

Treatment of status epilepticus

26
Q

Describe the distribution of benzodiazepines.

A

Bind strongly to plasma proteins

Highly lipid soluble

27
Q

Describe the metabolism of benzodiazepines.

A

Extensively metabolised in the liver

28
Q

Describe the excretion of benzodiazepines.

A

Excreted in the urine as glucuronide conjugates

29
Q

Describe the duration of action of benzodiazepines.

A

Varies a lot

This allows classification as short-acting and long-acting benzodiazepines

30
Q

What makes long-acting benzodiazepines have a long duration of action?

A

They have slower metabolism

They generate active metabolites

31
Q

Name two short-acting benzodiazepines.

A

Oxazepam

Temazepam

32
Q

Name a long-acting benzodiazepine.

A

Diazepam

33
Q

Describe the metabolism of oxazepam.

A

It is metabolised straight to its glucuronide conjugate (t1/2 = 8 hours)

34
Q

Describe the metabolism of temazepam.

A

Metabolised to oxazepam and then to the glucuronide conjugate

35
Q

Describe the metabolism of diazepam.

A

Metabolised via temazepam and oxazepam to the glucuronide conjugate
Some diazepam is metabolised to nordiazepam and then oxazepam

36
Q

Name three drugs that are used as anxiolytics.

A

General rule – long-acting benzodiazepines
Diazepam
Chlordiazepoxide
Nitrazepam

37
Q

Under what condition would you use a short-acting benzodiazepine as an anxiolytic?

A

Hepatic impairment – this means that the benzodiazepines and metabolised more slowly – drug of choice = oxazepam

38
Q

Name two drugs that are used as sedatives/hypnotics.

A

General rule – short-acting benzodiazepines
Oxazepam
Temazepam

39
Q

Name a long acting drug that might be used as a sedative/hypnotic.

A

Nitrazepam (t1/2 = 28 hours)

40
Q

What are the advantages of benzodiazepines over barbiturates?

A

Wide margin of safety
 Overdose causes prolonged sleep (but this is rousable)
 Flumezanil can be given IV if a patient has overdosed
Mild effect on REM sleep
Do NOT enhance liver enzymes

41
Q

What are the unwanted effects of benzodiazepines?

A

Sedation
Confusion
Ataxia
Potentiate other CNS depressants (e.g. alcohol)
Tolerance
Dependence
Free plasma concentration of benzodiazepines can be increased by giving aspirin and heparin

42
Q

Name a sedative/hypnotic that isn’t a benzodiazepine. What class of drug does this fall into?

A

Zopiclone – this is a cyclopyrrolone and it’s short-acting (t1/2 = 5 hours)
NOTE: it acts on the benzodiazepine receptor but it is not a benzodiazepine
This has fewer hangover effects but dependency is still an issue

43
Q

What drug is used to control the physical symptoms of anxiety?

A

Propranolol

44
Q

Name a new drug that has started being used as an anxiolytic.

A

Buspirone – 5HT1A agonist
This has relatively few side effects and causes less sedation than benzodiazepines
Downside: slow onset of action (maximal anxiolytic effects are not seen for a number of days/weeks)

Y2 LCRS 1 - Pharmacology and Therapeutics (38 decks)

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