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PR3136 PT4 > L02 Anxiolytics > Flashcards

L02 Anxiolytics Flashcards

1
Q

Differentiate anxiety from fear.

A

Differences:

  • Fear: response to imminent, clear & present danger or threat
  • Anxiety: response to anticipated, vague & ill-defined threat; more foreboding

Similarities:

  • For both fear & anxiety, threats may be real or perceived.
  • Response may include defensive behaviors, autonomic reflexes, arousal, corticosteroid production & negative emotions
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2
Q

At what point is anxiety considered to be a psychiatric disorder to be treated?

A

Normal: arousal, efficient, “fight or flight” response
Psychiatric: interferes w/ activities of daily living, work & relationships

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3
Q

How is anxiety manifested in patients diagnosed with generalised anxiety disorder (GAD)?

A

Psychological:

  • Negative emotions: worry, nervousness, unease
  • Arousal: mind is always alert/vigilant
  • Lack of concentration: result from a constant heightened state of brain activity (i.e. arousal)
  • Insomnia (due to constant aroused state)

AND/OR

Physical (adrenergic activation of “fight-or-flight”):

  • Tachycardia, SOB/tachypnea
  • Nausea, gastric acid hypersecretion
  • Trembling due to overactivation of skeletal muscles
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4
Q

Explain the biochemical basis behind the manifestation of anxiety states.

A

1) Central & peripheral adrenergic/noradrenergic activation i.e. “flight, fright, or fight response”
2) Hypothalamus-pituitary-adrenal (HPA) axis, leading to secretion of stress hormones i.e. cortisols

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5
Q

Explain how GAD is diagnosed in a patient.

A

Generalised Anxiety Disorder (GAD):

  • Excessive, uncontrollable worry over everyday matters
  • Interferes with daily functioning
  • Has BOTH psychological & physical symptoms
  • Diagnosed when present for at least 6 months
  • Most common cause of disability in workplaces
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6
Q

What are some other anxiety and fear disorders that may be diagnosed?

A

Triggers are more specific:

1) Post-traumatic stress disorders (PTSD):
- Specific anxiety response to a traumatic event
- Common in soldiers

2) Phobias: specific, unreasonable kind of fear

3) Panic disorder:
- Dramatic breakdown into a panic
- More acute presentation of anxiety disorder

4) Obsessive-compulsive disorder (OCD):
- More complex in nature, yet classical
- A mental state of an intrusive, persistent thought leading to a physical need to act in response to obsession

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7
Q

What is the therapeutic rationale behind the use of anxiolytics in the Tx of GAD?

A

MOA: CNS depression to reduce overactivation of adrenergic receptors

  • Effects of CNS depression is dose-dependent (i.e. closely-related)
  • Low dose: Anxiolytic & sedating
  • High dose: Hypnotic
  • Even higher dose: Anaesthesia used for surgery
  • Same drug CAN have more than one action depending on the dose (i.e. on a continuum & NOT mutually exclusive!!)
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8
Q

Differentiate the meaning of “sedative”, “hypnotic” & “anxiolytic” effects.

A

Sedative:

  • Causes sedation, relaxation
  • NOT necessarily losing consciousness

Hypnotic:

  • Induces drowsiness & sleep
  • May have amnestic effects

Anxiolytic:
- Reduces symptoms of anxiety

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9
Q

List the drug classes that may be used as sedative-hypnotics & anxiolytics for the Tx of GAD.

A

1) Benzodiazepines (BZD; -zepam / -zolam)
- Anxiolytics / Sedatives: Diazepam, lorazepam
- Hypnotics: Diazepam, triazolam, temazepam
- Pre-anaesthetics for surgery: Diazepam, midazolam
- Additional anticonvulsant/antiepileptic: Diazepam

2) Non-BZD:
- Barbiturates: Phenobarbital
- Buspirone
- Zolpidem
- Pregabalin
- Hydroxyzine
- Propranolol
- TCA: Clomipramine
- SSRI: Fluoxetine, citalopram, sertraline & paroxetine
- SNRI: Venlafaxine & duloxetine
- NaSSA: Mirtazapine

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10
Q

Explain the role of GABA-A receptors in the mediation of CNS depression when using anxiolytics.

A
  • GABA (gamma-aminobutyric acid) works as inhibitory neurotransmitters w/in brain & binds to GABA-A receptors Cl- channels.
  • Allows influx of Cl- ions from extracellular fluid to intracellular fluid upon GABA binding which reduces membrane potential
  • Subsequently reduce propensity for depolarisation
  • Results in slower / less active firing of action potential of neurons (i.e. inhibitory neurotransmission)
  • Consequently mediate CNS depressive effect (i.e. reduces neural excitability)
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11
Q

What is the mechanism of action of benzodiazepines (BZDs)?

A

BZDs allosterically binds to GABA benzodiazepine (allosteric) site, separate from primary GABA site.

  • Enhances GABA binding to GABA-A receptors
  • Potentiates influx of Cl- ions
  • Leads to hyperpolarisation by increasing frequency of GABA-induced channel opening
  • Subsequently reduced neural excitability (i.e. CNS depressive effect)

Thus, this results in:

  • Mood alteration via limbic system
  • Drowsiness via reticular activating system
  • Muscle relaxation via motor cortex
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12
Q

Name some examples of short-acting BZDs.

A

Complusory: Midazolam
Optional: Triazolam

Half-life = approx. 3-8 h

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13
Q

Name some examples of intermediate-acting BZDs.

A

Complusory: Lorazepam
Optional: Alprazolam, clonazepam, oxazepem, temazepam

Half-life = approx. 8-24 h

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14
Q

Name some examples of long-acting BZDs.

A

Complusory: Diazepam
Optional: Chlordiazepoxide, flurazepam

Half-life = approx. 1-3 days

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15
Q

Which BZDs can be used for the indication of status epilepticus (i.e. a form of epilepsy)?

A

Lorazepam & Diazepam

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16
Q

Which type of BZDs is indicated for induction of general anaesthesia or procedural sedation?

A

Short-acting BZDs: Midazolam, triazolam

17
Q

Which BZDs are not indicated for Tx of anxiety disorders?

A

Triazolam, temazepam & flurazepam

18
Q

Which drug is used for the reversal of acute toxicity / overdose of BZDs?

A

Flumazenil (BZD antagonist)

19
Q

What are some of the side effects of BZDs?

A

1) CNS depressive effects:
- Drowsiness
- Confusion
- Amnesia
- Impaired muscle coordination

2) Acute toxicity / overdose:
- Severe respiratory depression (esp. w/ concomitant use of alcohol)

3) Tolerance & dependence:
- Tolerance is dependent on frequency of use (develop faster for epilepsy than insomnia)
- Dependence can result in withdrawal effects if abrupt
- Withdrawal effects: Disturbed sleep, rebound anxiety, tremors & convulsions
- Has abuse potential

20
Q

Describe the clinical use of zolpidem in the Tx of anxiety disorders.

A

Zolpidem is primarily used to treat insomnia due to good hypnotic effect.
- NOT effective as anxiolytics

21
Q

Which non-BZD drug CANNOT be used for the Tx of anxiety disorders?

A

Zolpidem

22
Q

Describe the mechanism of action of zolpidem.

A

Potentiates GABA-A-mediated Cl- currents by binding allosterically at benzodiazepine site of GABA-A receptors.

23
Q

Describe the mechanism of action of buspirone.

A

Serotonin 5-HT1A receptor partial agonist & also binds to dopamine receptors.

24
Q

Which anxiety disorder is buspirone indicated for?

Is there a difference in therapeutic effect between buspirone and BZDs for this particular indication?

A

GAD, but onset of anxiolytic effect takes 1-2 weeks.
Lacks anticonvulsant & muscle relaxant properties.
- Due to different MOA (5-HT1A & dopamine agonism) unlike BZDs (via allosteric binding to GABA-A receptors Cl- channels)

25
Q

Describe the mechanism of action of barbiturates.

A

Potentiates GABA-A-mediated Cl- currents by binding allosterically at the barbiturate site of GABA-A receptors.
- Note that difference in allosteric binding site from BZDs & zolpidem!!

26
Q

Flumazenil is effective for treating barbiturate overdoses. True or false?

A

False! Flumazenil is an antagonist at BZD allosteric site of GABA-A receptors, NOT an antagonist at the barbiturate allosteric site!

27
Q

Why have barbiturates been largely replaced by BZDs for the Tx of anxiety disorders?

A
  • Higher tendency of barbituates to develop tolerance & dependence.
  • More severe withdrawal symptoms when used as sedative-hypnotic
  • At anaesthetic (i.e. very high) doses, barbiturates (e.g. phenobarbital) can directly open Cl- channels & block Na+ channels.
28
Q

Classify the types of barbiturates & describe their respective indications.

A

1) Ultrashort-acting (20 min): Thiopental (Thiopentone)
- Used for IV induction of general anaesthesia
- Primary use for barbiturates

2) Short-acting (3-8 h): Pentobarbital & amobarbital
- Used as sedative-hypnotic

3) Long-acting (1-2 days): Phenobarbital
- Used as last-line anticonvulsant / antiepileptic
- High abuse potential & severe withdrawal effects

29
Q

What are some side effects of barbiturates?

A

1) Greater tolerance & dependency than BZDs
2) More severe withdrawal effects than BZDs
- i.e. disturbed sleep, rebound anxiety, tremors & convulsions
3) Medullary depression & coma
- Impt. autonomic responses are heavily depressed at very high doses
- Absent in increasing dose of BZD due to plateau of dose-response curve, unlike positive correlation for barbiturates

30
Q

Describe the mechanism of action of pregabalin.

A

GABA analogue that increases synaptic GABA concentration, resulting in hyperpolarisation.

  • However, pregabalin does NOT act on GABA itself
  • Also acts on voltage-gated Ca2+ channels
31
Q

What indications can pregabalin be used in the Tx of anxiety disorders?

A

GAD & epilepsy

- Pregabalin has anticonvulsant effects.

32
Q

What important severe side effect is pregabalin known to be associated with?

A

Emergence of worsening of suicidal thoughts

- CONTRAINDICATED for pt. w/ depression!!

33
Q

Describe the mechanism of action of hydroxyzine.

A

First-generation antihistamine w/ 5-HT2 antagonism activity.

  • Has additional alpha-adrenergic receptor activity
  • Anxiolytic effects can be attributed to serotonergic antagonism of hydroxyzine
34
Q

What are some advantages of using hydroxyzine over BZD & barbiturates?

A

Low addictive potential compared to BZDs & barbiturates

Additional anti-itch & antiemetic properties that helps w/ itching & nausea symptoms associated w/ anxiety.

35
Q

What indications can propranolol be used in the Tx of anxiety disorders? How so?

A

Performance anxiety & social phobias.

Reduces physical symptoms associated with adrenergic activation due to beta-adrenergic receptor antagonism.
- CONTRAINDICATED in pt w/ asthma & heart conditions.

PR3136 PT4 (14 decks)

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