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PYB260 > W9 - Anxiolytics & Sedative-Hypnotics > Flashcards

W9 - Anxiolytics & Sedative-Hypnotics Flashcards

1
Q

What do anxiolytics and sedatives do?

A

Used to reduce anxiety, sedate, aid sleep, anticonvulsants & anesthetics

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2
Q

What are the three classes of drugs used to achieve these effects?

A

Benzodiazepines (BDZ), barbiturates, and other) - nave similar neural mechanisms

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3
Q

What is the administraton of BBTs and BDZs

A

• May be administered: orally, parenterally (including i.v. or i.m.), but absorption from digestive system better than i.m. absorption bc of biochemical properties

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4
Q

When are BBTs and BDZs readily absorbed?

A

After oral and parenteral routes

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5
Q

Are they acids or bases?

A

Weak acids

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6
Q

What is the absorption of barbiturates?

A
  • All barbiturates have pKa near 8.0 → almost entirely non ionized at pH of digestive system (∴ readily absorbed)
  • Variability in lipid solubility
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7
Q

What is the absorption of Bezodiazepines?

A
  • pKa of about 3.5 to 5.0 ∴ readily absorbed from digestive system
  • Range of lipid solubility
  • Absorption may be á by alcohol
  • Compete for same enzyme between benzos and alcohol
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8
Q

What is the distribution?

A
  • Determined by lipid solubility

* Cross placental barrier & present in breast milk

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9
Q

What happens with highly lipid soluble BBTs and BDZs

A

Cross BBB
• Different – more highly lipid soluble reach brain quickly but then redistributed very quickly to areas high in fat and then slowly released into bloodstream
→ effects may be seen quickly, but also dissipate quickly
• Drug released slowly from fat deposits → metabolized by liver

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10
Q

What is the excretion curve of BDZs?

A
  • 2-phase excretion curve (similar to cannabis):
  • Phase 1: rapid drop in blood level due to redistribution in fat deposits
  • Half-life ~ 2-10 hours
  • Phase 2: metabolism (liver, CYP450 enzyme)
  • Half-life ~ 27-48 hours (stay in system for long time)
  • Cant often talk about half life and active effect because of active metabolites – ongoing effect in terms of metabolism
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11
Q

Are older BDZs metabolized?

A
  • Fully metabolized, and the active metabolites of these drugs = duration of effect not determined by half-life
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12
Q

What effects the metabolism of BDZs?

A

Increased by repeated administration, slowed (for some BDZs) by alcohol (increased blood level of BDZs)

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13
Q

How are barbiturates excreted

A

Most fully metabolised by liver enzymes before excretion

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14
Q

Is there any cross tolerance of BBTs?

A

Yes - cross tolerance for people with alcohol dependence - if chronic alcohol user and is sober then is metabolised much more efficiently

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15
Q

What is metabolism increased by

A
  • Repeated administration
  • Anti-psychotics
  • chronic alcohol use
  • Antihistamines
  • nicotines
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16
Q

What do BBZs stimulate physiologically and what other drugs does this effect?

A
  • Stimulate enzymes and metabolizes drugs:
  • Chlorpromazine
  • Morphine
  • Caffeine
  • General and local anaesthetics
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17
Q

How can overdoses be treated?

A
  • By making urine more alkaline (because barbiturates are acidic)
18
Q

What receptors are affected?

A

GABAa receptors (ionotropic, mainly postsynaptic, quick response, coupled to Cl- channels)

19
Q

What are the receptors similar to?

A

Alcohol but not as diffuse (more specific than alcohol)

20
Q

How do they affect the receptor sites

A

Have their own receptor sites on GABA- Chloride Ionophore Complex

21
Q

How do they affect the ion channels?

A
  • Make GABA NT more effective at sites

- -> positive allosteric modulations, therefore increasing ability to open the channel

22
Q

What is the effect of opening the ion channel

A

More Cl- ions in postsynaptic neuron - increased inhibition

23
Q

What is barbiturates mode of action? How is this different from BDZs?

A
  • Increases the time of the channel being open - larger increase of Cl- (compared to BDZ)
24
Q

What is BDZs mode of action?

A
  • Increase frequency of channel opening and increased affinity of GABA for receptor
25
Q

What type of moderator is BDZs? How does this work?

A

Allosteric modulator - binds to a different site on the ion channel to increase it’s affinit for GABA - it is GABA that opens the channel

26
Q

What is the difference between BDZs and BBTs in how they work on the ionotropic receptor?

A

BDZs always JUST an allosteric modulator - increases GABA affinity. BBTs can also act directly on the receptor to open the channel - this is what can cause respiratory repression and death

27
Q

What is a negative GABA modulator

A

Decreased likelihood of channel opening

28
Q

What is the effect of BDZs on adenosine?

A

BDZs may also affect adenosine (inhibitory neurotransmitter) by blocking reuptake - enhances’s it’s effect (opposite to alcohol )

29
Q

What are the effects of BDZs and BBTs on dopamine

A

Decreased DA (dopamine) in nucleus accumbens - highly reinforcing (lots of GABA receptors in NA - may be a secondary inhibitory effect - inhibit some inhibitory processes

30
Q

What are the effects of BDZs on the body?

A
  • Mostly due to the effects on CNA
  • Relatively mild decreased respiration
  • Mild decreased BP
  • Increased appetite and weight gain
  • Increased muscle relaxation
  • –> possibilities for disorders like parkinson’s which originate in CNS but effect muscles
  • Anticonvulsant
31
Q

What are BDZs widely used for to do with sleep?

A
  • Widely used for S-H properties
32
Q

What are BDZs useful for to do with sleep?

A
  • short term intervention - but shouldn’t be prescribed for sedative purposes for more than 2 - 4 weeks
33
Q

What are the effects of BDZ on skeep

A

Decreased awakenings, Increased total sleep time, decreased REM and stage 3&4 sleep - withdrawal rebound effect

34
Q

Does tolerance to sleep effects develop?

A

No - the longer on the greater the rebound

BUT in order to eliminate rebound, re-adminster drug = dependence

35
Q

What are the subjective effects of BDZs

A
  • Sedation/fatigue/confusion
  • Euphoria & “liking”
  • Generally don’t report as pleasant unless they are dependent
  • Anxiolytics (but not in individuals with normal anxiety levels) – only works for people with clinical anxiety (even in this population only works for approx. 60 % people)
36
Q

What are the effects on vision?

A

Lowered visual and auditory acuity

37
Q

What are the implications of BDZs impact on reaction time?

A
  • Decreased simple RT (at high doses)

- -> Risky for tasks such as driving

38
Q

What are BDZ’s effects on memory

A

Explicit memory effected even at low doses

  • -> Anterograde amnesia (acquisition of new explicit information), but not implicit memory (skill acquisition)
  • -> Deficits observable on wide variety of tests
39
Q

Are there any situations in which BDZs would improve performance?

A

If the patient is clinically anxious

40
Q

What are the hangover effects of BDZs

A
  • Distribution of mood & performance 12 hourse after administration - Amplifies effects of alcohol
41
Q

What are the effects of BDZs on driving?

A
  • Increased collisions
  • Increased risk with alcohol
  • Increased risk in first-time users who usually report feeling fine
42
Q

What are the effects of BBTs on the body

A
  • Significant decrease in respiration
  • Decreased HR
  • Decreased BP
  • Can be used as anticonvulsants

PYB260 (9 decks)

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