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YR2 LCRS Pharm > 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 protein 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 + benzodiazepine receptor protein
Results in opening of the chloride ion channel, causing hyper polarisation of the cell

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4
Q

Name a competitive antagonist of the GABA A receptor protein.

A

Biciculline

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5
Q

Name a competitive antagonist of the benzodiazepine receptor protein. When is this used therapeutically?

A

Flumazenil

Used to treat Benzodiazepine OD

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6
Q

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

A

Facilitate GABA-mediated opening of cl- channel

Increase affinity of GABA to the GABA binding site– reciprocated with enhanced BZ binding

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7
Q

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

A

Enhance normal physiological action of GABA
Enhance GABA binding to the GABA receptor protein (NOT reciprocated)
At higher concs, BARBs can directly open Cl- channel

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8
Q

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

A

Benzodiazepines: increase frequency of cl- channel opening
Barbiturates: increase duration of cl- channel opening

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9
Q

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

A

Barbiturates are LESS selective
May explain why barbiturates induce surgical anaesthesia + are less safe than benzodiazepines
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 3 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

Sedatives/ 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 + 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

6-membered ring (4 carbons + 2 nitrogens)

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18
Q

Barbiturates have been largely superseded by benzodiazepines. Which barbiturate is still used relatively commonly? What is it used for? What is the half-life of this drug?

A

Amobarbital
Severe intractable insomnia
20-25 hours

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19
Q

What are 6 unwanted effects of barbiturates?

A

Low safety margin (depresses respiration, OD = lethal)
Alters natural sleep (reduced REM, causes hangovers)
Enzyme inducers (cause faster metabolism of other drugs + thus decreases their efficacy)
Potentiates action of other CNS depressants (e.g. alcohol)
Tolerance (Tissue + pharmacokinetic)
Dependence (withdrawal syndrome results)

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20
Q

What structure is common to all benzodiazepines?

A

They are tricyclic

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21
Q

What are the three key benzodiazepines?

A

Diazepam
Oxazepam
Temazepam

22
Q

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

A

Their pharmacokinetics

23
Q

Describe the administration of benzodiazepines.

A

Well absorbed per orally

Peak plasma concentration after ~ 1 hour

24
Q

When would you give IV benzodiazepines?

A

Treatment of status epilepticus

25
Q

Describe the distribution of benzodiazepines.

A

Bind strongly to plasma proteins

Highly lipid soluble, results in wide distribution

26
Q

Describe the metabolism of benzodiazepines.

A

Extensively metabolised in the liver

27
Q

Describe the excretion of benzodiazepines.

A

Excreted in the urine as glucuronide conjugates

28
Q

Describe the duration of action of benzodiazepines.

A

Varies a lot

Allows classification as short- + long-acting

29
Q

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

A

Have slower metabolism

Generate active metabolites

30
Q

Name two short-acting benzodiazepines.

A

Oxazepam

Temazepam

31
Q

Name a long-acting benzodiazepine.

A

Diazepam

32
Q

Describe the metabolism of oxazepam.

A

Metabolised straight to its glucuronide conjugate (t1/2 = 8 hours)

33
Q

Describe the metabolism of temazepam.

A

Metabolised to oxazepam, then to the glucuronide conjugate

34
Q

Describe the metabolism of diazepam.

A

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

35
Q

Name three drugs that are used as anxiolytics.

A

General rule: long-acting benzodiazepines
Diazepam
Chlordiazepoxide
Nitrazepam

36
Q

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

A

Hepatic impairment: means BZs are metabolised more slowly

Use oxazepam

37
Q

Name two drugs that are used as sedatives/hypnotics.

A

General rule: short-acting benzodiazepines
Oxazepam
Temazepam

38
Q

Name a long acting drug that might be used as a sedative/hypnotic. Why would this be used?

A

Nitrazepam (t1/2 = 28 hours)

If waking early or anxiolytic effect desired in day

39
Q

What are 5 advantages of benzodiazepines over barbiturates?

A

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

40
Q

What are 7 unwanted effects of benzodiazepines?

A

Sedation
Confusion
Ataxia
Potentiate other CNS depressants (e.g. alcohol)
Tolerance (tissue only)
Dependence (less intense withdrawal syndrome than BARBs)
Free plasma conc. can be increased by giving aspirin + heparin

41
Q

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

A

Zopiclone: a cyclopyrrolone + it’s short-acting (t1/2 = 5 hours)
acts on BZ receptor but not a BZ
Has fewer hangover effects but dependency is still an issue

42
Q

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

A

Propranolol
Tachycardia
Tremor

43
Q

Name a new drug that has started being used as an anxiolytic. What are its advantages and disadvantages?

A

Buspirone: 5HT1A agonist
Relatively few side effects + causes less sedation than BZs
Downside: slow onset of action (max. anxiolytic effects not seen for days/weeks)

44
Q

What is the precursor molecule to GABA? What enzyme causes the conversion to GABA?

A

Glutamate

Glutamate decarboxylase GAD

45
Q

What are GABA-B receptors?

A

GABA auto receptors on presynaptic nerve terminals

Regulate GABA release into synapse

46
Q

What type of GABA receptor is found on the post-synaptic membrane?

A

GABA-A receptors

47
Q

Describe the metabolism of GABA. What type of enzymes mediate this?

A

GABA reuptake into pre-synaptic or glial cells
GABA-T converts GABA to Succinic semialdehyde
SSDH converts this to Succinic acid
Mitochondrial enzymes

48
Q

What happens if metabolism of GABA is inhibited?

A

Increased inhibition of the brain

Used in treatment of epilepsy

49
Q

Why are barbiturates and benzodiazepines referred to as positive allosteric modulators?

A

Without GABA they have no action

They enhance action of GABA at GABA receptor

50
Q

What other classes of drugs can be used as anxiolytics?

A 
Some antidepressants e.g. SSRIs
Some antiepileptcs e.g. Valproate
Some antipsychotics e.g. Quetiapine
Propanolol
Busiprone

YR2 LCRS Pharm (34 decks)

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