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PYB260 > Week 11 - Anxiolytics & Sedatives > Flashcards

Week 11 - Anxiolytics & Sedatives Flashcards

1
Q

anxiolytics & sedative-hynotics

A

used to reduce anxiety, sedate, aid sleep, act as anticonvulsants and as anaesthetics

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2
Q

the three classes of drugs to achieve these effects

A
  • benzodiazepines
  • barbiturates
  • other
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3
Q

illicit use of BDZs

A
  • misused by those with drug addictions and used in ways that are not consistent with optimal therapeutic goals
  • combined with other drugs (opiates & alcohol)
  • controlled substances according to WHO standards
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4
Q

modern BDZs without active metabolites

A
  • ozazepam
  • temazepam
  • lorazepam
  • clonazepam
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5
Q

modern BDZs with active metabolites

A
  • diazepam
  • chlordiazepoxide
  • nitrazepam
  • alprazolam
  • flurazepam
  • bromazepam
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6
Q

examples of BBTs

A
  • secobarbital
  • phenobarbital
  • amobarbital
  • mephobarbital
  • secobarbital
  • aprobarbital
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7
Q

administration

A
  • orally, parenaterally (i.v., i.m.) absorption from digestive system better than i.m. absorption bc of biochemical properties
  • BBTs & BDZs readily absorbed after oral and parenteral routes
  • choice of route of admin depends on reason for use
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8
Q

Absorption - barbituates

A
  • weak acid
  • pKa near 8.0 - almost entirely nonionized at pH of digestive system - readily absorbed
  • variability in lipid solubility
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9
Q

absorption - benzodiazepines

A
  • weak acid
  • pKa of 3.5 to 5.0 readily absorbed from digestive dystem
  • range of lipid solubility
  • absorption may be increased by alcohol
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9
Q

distribution

A
  • determined by lipid solubility
  • cross placental barrier and present in break milk
  • highly lipid soluble will cross BBB, effects seen quickly but dissipate quickly
  • drug released slowly from fat deposits - metabolised by liver
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9
Q

2-phase excretion: BDZs

A

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)

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10
Q

excretion - BDZs

A
  • older BDZs almost fully metabolized - active metabolites of these drugs = duration of effect not determind by half-life
  • metabolism increased by repeated administration; slowed by alcohol
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10
Q

excretion - BBTs

A
  • most fully metabolized by liver enzymes before excretion
  • repeated admin = increase metabolism
  • metab also increased by anti-psychotics, anesthetics, chronic alcohol use, antihistamines, nicotine
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11
Q

excretion - BBTs (other drugs)

A
  • BBTs stimulate enzymes that metabolize other drugs (chlorpromazine, morphine, caffeine, general and local anesthetics)
  • ODs can be treated by making urine more alkaline
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12
Q

how do they affect GABA receptors

A
  • ionotropic, mainly postsynaptic, quick response, couple to Cl- channels
  • own receptor sites on GABA-Chloride Ionophore Complex
  • make GABA NT more effective at these sites: increases ability to open channel
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13
Q

BBT vs BDZ mode of action

A

BBTs: increase time channel is open creates larger increases of Cl-
BDZs: increases frequency of channel opening & increases affinity of GABA for receptor

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14
Q

neurophysiology

A
  • some act as negative GABA modulators
  • interact with their own receptor sites
  • BDZs affect adenosine by blocking re-uptake
  • increases dopamine in nacc via GABA
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15
Q

BDZ effects on the body

A
  • relatively mild decrease in respiration
  • mild decrease in blood pressure
  • increase appetite/ weight gain
  • increase muscle relaxation
  • anticonvulsant - petit mal seizures & infantile spasms
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15
Q

BDZs effect on sleep

A
  • widely used for sedative-hypnotic properties
  • effective as short-term intervention
  • decreases time to fall asleep; decreases awakening and REM & stage 3 & 4 sleep, increase total sleep time - withdrawal rebound effect
  • tolerance to effects does not develop
  • eliminate withdrawal rebound by re-administer drug
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15
Q

BDZs subjective effects

A
  • sedation/fatigue/confusion
  • euphoria & ‘liking’
  • anxiolytics
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16
Q

BDZs effects on performance

A
  • decreased visual & auditory acuity
  • decreased simple RT (at high doses)
  • explicit memory - anterograde amnesia, not implicit memory
  • if clinicallty anxious, BDZs may improve performance
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17
Q

BDZs hangover effects

A
  • disruption in mood and performance 12 hrs after admin
  • amplifies effects of alcohol
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18
Q

BDZs effects of driving

A
  • increases collisions
  • increased by alcohol
  • increased risk in first time users who report feeling fine
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19
Q

BBTs effects on the body

A
  • significant decrease in respiration
  • heart rate
  • blood pressure
  • anticonvulsants
20
Q

BBTs effects on sleep

A
  • sleeping pills - decreased sleep onset latency; increased total sleep time
  • decrease REM sleep - tolerance after 1 week
  • withdrawal rebound up to 40% of sleep time for several weeks
21
Q

BBTs subjective effects

A

similar to benzodiazepines

22
Q

BBTs effects on performance

A
  • decreased visual acuity
  • overestimate time
  • decreased steadiness
  • decreased visual tracking
  • decreased divided attention
  • decreased athletic performance
23
Q

BBTs hangover effects

A
  • simple RT deficits detcted the next day
  • decreased pursuit tasks
  • decreased body steadiness after 18 hours
24
Q

BBTs effects on driving

A

equivalent to BAL of .15

25
Q

unconditioned behaviour

A
  • taming seen in lab animals first
  • restricted to decreased defensive aggression
26
Q

conditioned behaviour

A
  • increased responding to punished stimuli
  • decreased avoidance behaviour
27
Q

discrimination - barbituates

A
  • not able to discriminate different types of BBTs
  • generalized to other BBTs, BDZs - not to amphetamines or LSD
  • can discriminate alcohol
28
Q

discrimination - benzodiazepines

A
  • animals readily discriminate BDZs from saline
  • generalize to other BDZs & BBTs but not antipsychotics
  • discrim effects can be blocked by drugs that block BDZ receptor
29
Q

Chronic tolerance- barbituates

A

develop at different rates for different effects
examples:
- antiepileptic effects = no tolerance
- RT/coordination ~ 1 week
- total sleep time ~ 70 days

30
Q

acute tolerance - benzodiazepines

A
  • can develop during single administration
  • behaviour and motor-imparing effects
31
Q

chronic tolerance - benzodiazepines

A
  • depressant effects develop tolerance 1st
  • locomotor, ataxic, muscle relaxant & anticonvulsant effects
  • anti-anxiety: variable in humans
  • drowsiness
  • sleep: after ~ 4wks
  • short-acting drugs avoid residual effects but progess to tolerance quicker
  • REM suppression does not develop tolerance
32
Q

cross-tolerance - barbituates

A
  • cross tolerant with each other, alcohol & BDZs
  • considerable cross-tolerance with other depressants
  • cross-tolerance with metabolizing enzymes induce by BBTs
33
Q

cross-tolerance - benzodiazepines

A
  • other depressant drugs
  • alcohol & BBTs
34
Q

BBT withdrawal

A

low doses - REM rebound
high doses - can precipitate medical emergency
- symptoms commence 12-24 hrs (or 48-72 hrs for long acting) after final dose and may last up to 2 wks

35
Q

symptoms of BBT withdrawal

A
  • tremors
  • anxiety
  • insomnia
  • nausea
  • delirium
  • seizures - death
  • hallucinations
  • disorientation
  • confusion
  • fear
  • agitation
  • REM rebound
    most symptoms gone in 2 wks similar to high-dose BDZ withdrawal
36
Q

2 types of BDZ withdrawal

A
  • sedative-hypnotic withdrawal
  • low-dose withdrawal
37
Q

Sedative-hypnotic withdrawal

A
  • occur with high doses > ~ 1month
  • usually seen in benzodiazepines with short half-lives
  • usually gone <10 days
  • sensitive to resuming treatment
  • notable symptoms: tremors, cramps, delirium, convulsions
38
Q

low-dose withdrawal

A
  • occur when low doses taken for extended periods (>6mnths)
  • duration 2 weeks or up to a year
  • usually come in waves
  • sensitive to resuming treatment
  • notable symptoms: anxiety, panic, irregular HB, decreased memory and concentration, increased BP, sensory sensitivity, distortion of reality
39
Q

BBT self-administration in animals

A
  • reinforcing properties using various reinforcement schedules
  • reinforcement properties of short vs long-acting barbituates
  • monkeys increase consumption until stable, then constant level of admin
40
Q

BDZ self-administration in animals

A
  • IV and oral
  • short & long acting
  • not as reinforcing as BBTs
  • reinforcing properties can be enhanced by priming with the drug, BBTs or other BDZs
  • longer acting BDZs, past use determines how reinforcing they are
41
Q

BBT experimental self-administration in humans

A
  • not chosen more often than placebo in lab studies
  • reinforcing for those with a history of use
42
Q

BBT non-experimental self-administration in humans

A
  1. street use
    - usually in high-dose binges combined with other drugs
    - injected with heroin or amphetamines
  2. Iatrogenic use
    - initially prescribed for variety of symptoms
    - reinforcing properties lead to abuse & doctor shopping
43
Q

BDZ experimental self-administration in humans

A

not chosen more often than placebo in lab studies even by those with high anxiety

44
Q

BDZ non-experimental self-administration in humans

A
  1. street use
    - usually combined with another drug (alcohol/methadone)
    - rohypnol
  2. Iatrogenic use
    - prescribed for anxiety
45
Q

BBTs effects on reproduction

A
  • baby goes through withdrawal when born - onset 7 days
  • birth defects
  • cleft lip & palate
  • abnormalities of heart, skeleton & CNS
  • brain weight
  • neurological development
  • decreased later male sexual behaviour (decreased testosterone)
  • learning disabilities, decreased IQ and psychosocial problems
46
Q

BBTs overdose

A
  • low TI
  • additive effect with alcohol - BAL .1 + .5mg secobarbital = lethal
  • poisoning causes unconsciousness, decrease HR & BP, blisters, decreased urine flow, decrease temperature regulation, respiratory depression
47
Q

BDZs on reproduction

A
  • suggestion that BDZ cause birth defects (fetal benzodiazepine syndrome similar to FAS)
  • withdrawal in infants similar to opiate withdrawal, start <2.5-6hrs after delivery
  • floppy baby syndrome after BDZ delivery process
48
Q

BDZ overdose

A
  • not as dangerous as BBT OD; seldom fatal on its own
  • sleep/drowsiness, no coma or severe respiratory depression
  • intensify depressant effects of alcohol and BBTs - combo of these in OD usually fatal
  • can be treated with BDZ receptor antagonist
49
Q

BDZ use as anxiolytic or s-h

A
  • symptomatic
  • underlying cause of anxiety/insomnia remains untreated
  • rebound insomnia/ rebound anxiety
50
Q

BDZ on sleep

A

disruption to sleep architecture may have harmful effects (re chronic REM sleep deprivation)

51
Q

BDZ over sedation

A

2 mechanisms
1. risk increase with BDZ with active metabolite (when used for anxiolytic or s-h purposes)
2. when use is combined with additional CNS depressants

52
Q

BDZ on memory

A
  • appears to impair memory
  • nature of impairment: intentional retrieval; explicit memory
  • significant drug related impairtment on average 82% of the times tested
53
Q

BDZ effects on older people

A
  • older people sensitive to CNS depressant effects
  • may cause confusion, amnesia, ataxia & pseudodementia
  • recommendations to minimise harm ( 1/2 regular adult dose, short term use, use without active metabolites)
54
Q

BDZ dependency

A
  • dependency leads to chronic use
  • withdrawal should be done under medical supervision to avoid convulsions, respiratory failure
  • involves gradual reduction of dose over 8-12 weeks
  • alternative coping strategies are essential
  • longer term management may be needed to avoid relapse

PYB260 (10 decks)

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