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LCRS Pharmacology and Therapeutics > Anxiolytics and hypnotics > Flashcards

Anxiolytics and hypnotics Flashcards

1
Q

What sort of receptors are involved with anxiolytics and hypnotics?

A

GABA-A receptors

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2
Q

What are the four proteins that GABA-A is composed of?

A

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

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3
Q

What does GABA modulin do?

A

Links together the GABA receptor protein and benzodiazepine receptor protein

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4
Q

Where does GABA bind to GABA-A?

A

The GABA receptor protein

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5
Q

What does binding of GABA to GABA receptor protein allow?

A

It allows GABA modulin to link together the GABA receptor protein and benzodiazepine receptor protein

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6
Q

What is the normal physiological action of GABA modulin?

A

It allows GABA receptor protein and benzodiazepine receptor protein to link and results in opening of chloride channel protein

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7
Q

What is bicuculline?

A

Competitive antagonist for GABA-A receptor

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8
Q

Where does benzodiazepine bind to GABA-A?

A

Benzodiazepine receptor protein

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9
Q

What are the two main effects of benzodiazepine binding that facilitates GABA-mediated inhibition?

A

Facilitates GABA-mediated opening of the chloride channel
Facilitates binding of GABA to its own binding site- increases the affinity of binding of GABA to the GABA binding site.
This effect is then reciprocated

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10
Q

What is flumezanil?

A

Competitive benzodiazepine antagonist

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11
Q

Where do barbiturates bind?

A

They bind to the barbiturate receptor protein

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12
Q

What are the 3 effects of barbiturates on GABA neurotransmission?

A

Facilitates GABA mediated opening of the Cl- channel
Facilitates GABA binding to its receptor but this isn’t reciprocated
At higher concentrations, barbiturates can have direct action on chloride channel

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13
Q

How effective are benzodiazepine and barbiturates without GABA?

A

They have no activity alone

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14
Q

How do benzodiazepine and barbiturates have an action?

A

They enhance the action of GABA, not direct GABA agonists

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15
Q

How do benzodiazepines and barbiturates have an allosteric action (at a different site)?

A

They bind to the GABA-A receptor but bind to their own binding sites on GABA-A

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16
Q

How are barbiturates and benzodiazepines different in terms of mechanism?

A

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

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17
Q

Why are barbiturates less safe than benzodiazepines?

A

Barbiturates are less selective

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18
Q

What can barbiturates be used for that benzodiazepines can’t?

A

Induction of surgical anaesthesia due to reduced selectivity

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19
Q

What are the clinical uses of benzodiazepines and barbiturates?

A 
Anaesthetics:
 -Barbiturates only: Thiopentone
Anti-convulsants:
 -Diazepam (bdzp)
 -Clonazepam (bdzp)
 -Phenobarbital (barb)
Anti-spastics
 -Diazepam
Anxiolytics
Sedative
20
Q

How can diazepam be used an an anti-spastic?

A

It is action in the spinal cord and reduces the propagation of action potentials in alpha motor neurones

21
Q

What is an anxiolytic?

A

It removes anxiety without impairing mental or physical activity (minor tranquillisers)

22
Q

What is a sedative?

A

It reduces mental and physical activity without producing loss of consciousness

23
Q

What is a hypnotic?

A

Induces sleep

24
Q

What should the ideal anxiolytics, sedatives and hypnotics be like?

A 
Have wide margin of safety
Not depress respiration
Produce natural sleep (hypnotics)
Not interact with other drugs
Not produce hangovers
Not produce dependence
25
Q

What do all barbiturates have in common structurally?

A

Barbiturate ring- common six membered ring with 4 carbons and 2 nitrogens

26
Q

What is amobarbitral used in?

A

Severe intractable insomnia

27
Q

Why are barbiturates not first choice drugs for sedative/hypnotic action?

A

Low safety margin- depress respiration and overdose could be lethal
Alter natural sleep (decrease REM sleep)- give rise to hangovers and cause irritability
Enzyme inducers (of liver microsomal enzymes- have to be careful when co-adminstering
Potentiate the effect of other CNS depressants
Tolerance
Dependence-associated with withdrawal syndrome:
-insomina, anxiety, tremor, convulsions and death

28
Q

What common structure are benzodiazepines?

A

They are tricyclic compounds that differ in their R1, R2 and R3 groups

29
Q

What are the three key benzodiazepines?

A

Diazepam
Oxazepam
Temazepam

30
Q

What is flumezanil?

A

Competitive benzodiazepine receptor antagonist

31
Q

Why is flumezanil so effective?

A

It has the same three ring structure as the agonist so it can bind to benzodiazepine receptor but has no efficacy

32
Q

What is the key difference between all benzodiazepines?

A

Pharmacokinetics (they all have similar potencies and same mechanism)

33
Q

How are benzodiazepines administered?

A

They are well absorbed per orally
They reach peak plasma concentration after about 1 hour
Sometimes given IV (treatment of status epileptics)

34
Q

How are benzodiazepines distributed?

A

They bind to plasma proteins strongly

Highly lipid soluble

35
Q

How are benzodiazepines metabolised?

A

Extensively in the liver

36
Q

How are benzodiazepines excreted?

A

In the urine as glucuronide conjugates

37
Q

How much does the duration of action of benzodiazepines change?

A

It varies a lot, allows classification as short acting or long acting (slower metabolism or generates active metabolites)

38
Q

Name short acting and long acting benzodiazepines?

A 
Short acting:
Oxazepam
Temazepam
Long acting:
Diazepam
39
Q

How is oxazepam metabolised?

A

In the liver to its inactive glucuronide

40
Q

How is temazepam metabolised?

A

Initially to oxazepam which is then converted to the glucuronide conjugate

41
Q

How is diazepam metabolised?

A

IT is metabolised via temazepam and oxazepam to the glucuronide

42
Q

What are benzodiazepines used for?

A

Anxiolytics (generally longer acting)
-Diazepam, chlordiazepoxide and nitrazepam
Sedative/hypnotics (generally shorter acting)
- Temazepam and oxazepam

43
Q

What are the advantages of benzodiazepines over barbiturates?

A

Wide margin of safety
Prolonged sleep if overdose but it is rousable
Flumanezil can be given to reverse overdose
Mild effect on REM sleep
Doesn’t enhance liver enzymes

44
Q

What are the unwanted effects benzodiazepines?

A 
Sedation
Confusion, ataxia
Potentiate other CNS depressants 
Tolerance
Dependence- withdrawal syndrome 
Free plasma concentration can increase by giving aspirin and heparin
45
Q

What is zopiclone?

A

It is short acting sedative/hypnotic at benzodiazepine receptor but isn’t a benzodiazepine. It enhances GABA-mediated neurotransmission by binding to the benzodiazepine binding site but is actually a cyclopyrrolone. It has similar efficacy to benzodiazepines and minimal hangover effects

46
Q

What can propranolol be used for?

A

It can be used as an anxiolytic because it is a non-selective beta blocker. Improves physical symptoms of anxiety- tachycardia and tremor

47
Q

What is buspirone used for?

A

It is used an anxiolytic because it is a 5HT1a agonist, has few side effects and there is less sedation compared to benzodiazepines.
Downside is slow onset of action

LCRS Pharmacology and Therapeutics (33 decks)

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