Clinical Pharmacology of Sedatives Flashcards

1
Q

what is a tranquilizer and examples

A

relieves anxiety without drowsiness

ex. phenothiazines, butyrophenones

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2
Q

what are neuroleptics and examples

A

tranquilizer used in treatment of psychoses

ex. penothiazines

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3
Q

what are sedatives and examples

A

calming effect with drowsiness

ex. alpha 2 adrenoreceptor agonists

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4
Q

what are hypnotics

A

induce sleep

ex. benzodiazepines, propofol

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5
Q

what is the mechanism of action of acepromazine

A

non-selective dopamine antagonism

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6
Q

what is the effect of acepromazine

A
  1. tranquilization/sedation
  2. anti-emesis
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7
Q

what other receptor types does acepromazine antagonize and what do these cause

A
  1. alpha 1 adrenergic receptors: vasodilation and hypotension
  2. muscarinic: decrease GIT motility
  3. histamine H1
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8
Q

what are the cardiovascular effects of acepromazine

A
  1. vasodilation leading to hypotension
  2. anti-arrhythmic action
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9
Q

why does acepromazine cause vasodilation and hypotension

A

alpha 1 adrenergic antagonist causes drop in BP initially

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10
Q

how does acepromazine cause ant-arrhythmic action

A

increases threshold for adrenaline/epinephrine induced arrhythmia

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11
Q

what are the respiratory effects of acepromazine

A

in bracycephalics sometimes causes an effect

sedation may worsen or improve the distress

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12
Q

what are the GI tract effects of acepromazine

A
  1. reduced smooth muscle activity
  2. anti-sialagogue action: reduced saliva
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13
Q

what are the other effects of acepromazine (4)

A
  1. hypothermia: peripheral vasodilation
  2. penile prolapse and/or priapism –> paramphimosis
  3. decrease in hematocrit
  4. mild anti-histamine activity
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14
Q

what are the routes of admin of acepromazine

A

IM (IV, SC)

oral pastes/tablets (20-55% oral bioavailability)

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15
Q

what is the duration of action of acepromazine

A

up to 4 hours or more

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16
Q

where is acepromazine metabolized

A

liver

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17
Q

what are potential drug interactions of acepromazine

A

potentiates effects of opioids, injectable and inhaled anethetics

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18
Q

what are the clinical indications of acepromazine (4)

A
  1. premedication prior to general anesthesia
  2. sedation
  3. motion sickness
  4. “calming” effects
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19
Q

what are the contra-indications of acepromazine

A
  1. hypovolemia
  2. breeding bulls and stallions
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20
Q

what are the cautions of acepromazine in some breeds (2)

A
  1. brachycephalic & giant breeds: increased sensitivity
  2. vasovagal syncope in boxers
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21
Q

what is vasovagal syncope in boxers caused by acepromazine

A

vasodilation leads to hypotension and then inappropriate bradycardia causing the dog to faint

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22
Q

how is vasovagal syncope treated in boxers after acepromazine administration

A

anti-muscarinic drugs –> atropine +/- fluids

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23
Q

how do you prevent the vasovagal syncope in boxers after acepromazine

A

use lower doses

or combine with anti-muscarinic

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24
Q

what is the mechanism of action of butyrophenones

A

dopamine antagonism

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25
Q

what are the effects of butyrophenones

A
  1. sedation/tranquilization
  2. anti-emesis
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26
Q

what are the side effects of butyrophenones

A
  1. vasodilation & hypotension (a1 adrenergic antagonism)
  2. hallucinations
  3. agitation
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27
Q

what are examples of butyrophenones

A
  1. azaperone (Stresnil)
  2. fluanisone + fentanyl (Hypnorm)
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28
Q

what is azaperone used for

A

sedation, premedication or behavioural modificaiton in pigs

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29
Q

how is azaperone administered

A

deep IM

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30
Q

what are the side effects of azaperone

A
  1. hypotension (mild)
  2. hypothermia
  3. priapism
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31
Q

what is hypnorm used for

A

sedation and premedication in mice, rats, rabbits, guinea pigs

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32
Q

how is hypnorm administered

A

IM or IP

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33
Q

what can hypnorm antagonize

A

fentanyl (ex. butorphanol)

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34
Q

what are examples of benzodiazepines

A
  1. diazepam (Valium)
  2. midazolam (Hypnovel)
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35
Q

what is the mechanism of action of benzodiazepines

A

potentiate activity of inhibitory neurotransmitter GABA

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36
Q

what are the effects of benzodiazepines

A
  1. anxiolytic action
  2. muscle relaxation
  3. anticonvulsant properties
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37
Q

what are the side effects of benzodiazepines

A
  1. minimal CV and respiratory depression

suited to the sicker patient

  1. hepatic failure in cats treated with oral diazepam
38
Q

can you get predictable sedation with benzodiazepines

A

no not in healthy patients

more reliable in sicker patients

39
Q

what is the route of administration of benzodiazepines

A

IV (IM) or oral route (well absorbed orally)

40
Q

what is the onset and duration of benzodiazepines

A

rapid onset

short duration (injection)

41
Q

how are benzodiazepines metabolized

A

liver

active metabolites of diazepam

42
Q

what are drug interactions with benzodiazepines

A

elimination impaired by microsomal enzyme inhibitors

ex. cimetidine + diazepam and erythromycin + midazolam

43
Q

what are the clinical uses of benzodiazepines

A
  1. premed/hypnosis of sick animals
  2. prevention/treatment of seizures
  3. muscle relaxation
  4. to induce eating in cats
  5. occasionally to modify behaviour
44
Q

what are the contraindications of benzodiazepines (2)

A
  1. hepatic encephalopathy (portosystemic shunts)
  2. early pregnancy (teratogenic)
45
Q

what are the formulations of diazepam and midazolam

A

diazepam: insoluble in water –> propylene glycol but irritant to veins (Valium), lipid emulsion but reduced bioavailability (Diazemuls)
midazolam: water soluble

46
Q

which is more potent midazolam or diazepam

A

midazolam > diazepam (~2x)

47
Q

what is diazepam licensed in

A

dogs and cats

48
Q

what is midazolam licensed in

A

horses

49
Q

what is the mechanism of action of alpha2-adrenoreceptor agonists

A

activate adrenergic receptors within the sympathetic nervous system

50
Q

which receptors can alpha2-adrenoreceptor agonists act on

A
  1. pre-synaptic a2 receptors
  2. post-synaptic a2 receptors
  3. post-synaptic a1 receptors
51
Q

what are the effects of alpha2-adrenoreceptor agonists on pre-synaptic a2 receptors

A

reduce noradrenaline release –> sympatholytic –> decrease in sympathetic tone

52
Q

what is the mechanism of action alpha2-adrenoreceptor agonists has on post-synaptic a2 receptors

A

mimic noradrenaline –> sympathomimetic –> increase sympathetic tone

53
Q

what is the mechanism of action alpha2-adrenoreceptor agonists has on post-synaptic a1 receptors

A

mimic noradrenaline –> sympathomimetic –> increase sympathetic tone

54
Q

what mechanism of action does alpha2-adrenoreceptor agonists have on the CNS

A

mainly act on pre-synaptic a2 receptors

reduce central sympathetic tone –> sympatholytic

55
Q

what is the mechanism of action of alpha2-adrenoreceptor agonists on peripheral nervous system

A

post- (pre-) synaptic a2 receptors

post-synaptic a1 receptors –> sympathomimetic

dominate form is post synaptic

56
Q

what are the effects of alpha2-adrenoreceptor agonists on the CNS

A
  1. sedation: mild to profound, more reliable than with tranquilizers
  2. analgesia
  3. muscle relaxation
57
Q

what are the effects of alpha2-adrenoreceptor agonists on the cardiovascular system (2)

A
  1. vasoconstriction
  2. bradycardia & reduced CO
58
Q

what does alpha2-adrenoreceptor agonists vasoconstriction in the blood vessels cause

A

increase in BP

59
Q

why do alpha2-adrenoreceptor agonists cause vasoconstriction

A

peripheral post-synaptic a2 receptors –> vasoconstriction (dominate effect)

peripheral post-synaptic a1 receptors –> vasoconstriction

central pre-synaptic a2 receptors –> vasodilation

60
Q

how do alpha2-adrenoreceptor agonists cause bradycardia & reduced CO

A

baroreceptor mediated response –> because of vasoconstriction to minimize the increase in BP

central pre-synaptic a2 receptors (decrease sympathetic tone) –> contributes to bradycardia

61
Q

explain the effects after administration of alpha2-adrenoreceptor agonists (4)

A
  1. initial vasoconstriction & increased BP
  2. heart rate falls
  3. BP returns to normal
  4. heart rate remains low as central effects begin to dominate

biphasic response (increase BP then decrease BP) described in humans but hypotension is not seen in animals

62
Q

what are respiratory effects that alpha2-adrenoreceptor agonists cause (2)

A
  1. mild to moderate depression (dose dependent)
  2. arterial hypoxemia in ruminants (especially sheep)
63
Q

what are the GIT effects alpha2-adrenoreceptor agonists cause (2)

A
  1. vomiting in some species
  2. reduced gut motility
64
Q

what are the endocrine effects that alpha2-adrenoreceptor agonists cause (2)

A
  1. inhibit ADH release –> diuresis (increased production of dilute urine)
  2. inhibit insulin release –> hyperglycemia (be aware if getting a blood sample from a sedated animal)
65
Q

what are the urogenital effects alpha2-adrenoreceptor agonists cause

A
  1. uterine contraction
66
Q

how are alpha2-adrenoreceptor agonists administered

A

IM, IV, SC & epidural routes

67
Q

how are oral routes of alpha2-adrenoreceptor agonists metabolized

A

oral route - high 1st pass metabolism

oral transmucosal route may be useful in aggressive patients

68
Q

what can be used to antagonize alpha2-adrenoreceptor agonists

A

alpha2 antagonists

they also antagonize analgesia

69
Q

what are the drug interactions of alpha2-adrenoreceptor agonists

A

marked anesthesia-sparing effect

act synergistically with opioids

much greater sparing effect than ACP

70
Q

what are clinical use of alpha2-adrenoreceptor agonists

A
  1. sedation/premedication
  2. analgesia
  3. offset ketamine hypertonicity
71
Q

what are alpha2-adrenoreceptor agonists licensed in

A

dogs, cats, horses and cattle

72
Q

what are the contraindications of alpha2-adrenoreceptor agonists

A

generally reserved for use in healthy patients

care with CV disease or in poor general health

73
Q

what are authorized alpha2-adrenoreceptor agonists

A

xylazine, detomidine, romifidine, medetomidine, dexmedetomidine

74
Q

what alpha2-adrenoreceptor agonists are licensed in dogs and cats

A

medetomidine, dexmedetomidine, (xylazine), atipamezole

75
Q

what alpha2-adrenoreceptor agonists are licensed in horses

A

xylazine, detomidine, romifidine

76
Q

what alpha2-adrenoreceptor agonists are licensed in cattle

A

xylazine, detomidine

77
Q

what is the selectivity difference for a2,a1 receptors

A

a2:a1 ratio

xylazine 160:1

detomidine 260:1

medetomidine 1620:1

78
Q
A
79
Q

what are the potency differences in different species of what alpha2-adrenoreceptor agonists

A

xylazine more potent in ruminants than horses

detomidine approx equipotent in ruminants and horses

pigs are relatively resistant to a2 agonists

80
Q

what alpha2-adrenoreceptor agonists has the longest duration

A

xylazine < detomidine/medetomidine < romifidine

81
Q

which alpha2-adrenoreceptor agonists is pro-arrhythmic

A

xylazine

82
Q

which alpha2-adrenoreceptor agonists is anti-arrhythmic

A

medetomidine may be

83
Q

which alpha2-adrenoreceptor agonist causes less ataxia in horses

A

romifidine –> less ataxia than other alpha2-adrenoreceptor agonists

84
Q

which alpha2-adrenoreceptor agonist causes uterine contraction

A

xylazine

85
Q

which alpha2-adrenoreceptor agonist causes vomiting in dogs and cats

A

xylazine > medetomidine

86
Q

what is the difference between medetomidine and dexmedetomidine

A

medetomidine is a racemic mixture of 2 optical isomers

dexmedetomidine is the active form and levomedetomidine is inactive (but may delay hepatic metabolism of other drugs)

87
Q

what is vatinoxan

A

peripheral alpha2 antagonist

88
Q

what does vatinoxan cause

A
  1. acts peripherally to less CV effects –> reduces vasoconstriction & resultant bradycardia/reduced CO
  2. unable to cross blood-brain barrier –> centrally mediated sedation, muscle relaxation and analgesia
89
Q

how do you chose a sedative

A
  1. side effects/”safety”
  2. reliability of sedation
  3. pharmacokinetics
  4. legislation
  5. potency
  6. cost
90
Q

which produces the most reliable sedation

A

alpha2 agonists > ACP > benzodiazepines