Sedatives Flashcards

1
Q

what classes are in sedative hypnotics?

A

phenothiazine derivatives
butyrophenone derivatives
benzodiazepine derivatives
alpha-2-adrenergic receptor agonists

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2
Q

what is the most common phenothiazine derivative?

A

acepromazine

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3
Q

what do phenothiazine derivatives do?

A

neuroleptics
major tranquilizer
antiemetic

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4
Q

what is the mechanism of action for phenothiazine derivatives?

A

D2 antagonist
sedate by inhibiting postsynaptic central dopaminergic receptors
D2 receptors are GPCRs
D2 receptors in chemoreceptor trigger zone produce antiemetic effects
peripherally block norepinephrine from binding alpha1 adrenergic receptors: peripheral vasodilation

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5
Q

what are the indications of phenothiazine derivatives?

A

routine sedation
preanesthetic period
often combined with opioids to produce synergic effects of each class (better sedation and analgesia)

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6
Q

what are some butyrophenone derivatives?

A

haloperidol
doperidol

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7
Q

what are butyrophenone derivatives?

A

antipsychotics

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8
Q

what is the mechanism of action for butyrophenone derivatives?

A

D2 antagonist
D1, 5HT, alpha1, and histamine antagonist

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9
Q

what are the indications for butyrophenone derivatives?

A

azaperone for swine for calming effects (mixing weanlings and feeder pigs)
transportation
obstetrical conditions
anesthetic adjunct for wildlife

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10
Q

what are the benzodiazepine derivatives?

A

diazepam (valium)
midazolam
lorazepam
zolazepam

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11
Q

what is the mechanism of action for benzodiazepine derivatives?

A

increase frequency of the opening of the chloride ion channel
majority GABAa receptors in cerebral cortex, very few outside of CNS
synergistic effect with barbituates

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12
Q

what are the indications for benzodiazepines?

A

anticovulsants
adjuncts to anesthetic induction agents
skeletal muscle relaxants
behavioral modification (anxiolysis and sedation)

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13
Q

what are the CNS effects of benzodiazepines?

A

often sedation
when administered alone: different effects can occur (excitement, agitation, vocalization, dysphoria)
reduction in cerebral blood flow and oxygen consumption

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14
Q

what are some side effects of benzodiazepines?

A

minimal cardiovascular effects
may decrease respiratory rate bur rarely affect ventilation and oxygenation at clinical doses (dose dependent respiratory depression)
relaxation, ataxia, recumbency in musculoskeletal
no analgesia

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15
Q

do benzodiazepines have analgesia effect?

A

no

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16
Q

when can benzodiazepines cause respiratory depression?

A

higher doses
exacerbated by other CNS depressants or in debilitated patients

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17
Q

where do many of the side effects of diazepam hydrochloride (valium) arise from?

A

vehicle: propylene glycol

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18
Q

what side effects can propylene glycol have?

A

hemolysis (especially in cats)
pain on infusion

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19
Q

what can repeated PO administration of diazepam hydrochloride lead to in cats?

A

hepatic necrosis

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20
Q

in what species does diazepam hydrochloride have a shorter half life?

A

dogs and cats compared to horses and primates

21
Q

is midazolam maleate water or lipid soluble?

A

water soluble for administration
lipid soluble in body

22
Q

why is midazolam becoming more popular in veterinary medicine than diazepam?

A

does not require propylene glycol
cheaper

23
Q

why is lorazepam (ativan) used in veterinary medicine?

A

anxiolytic

24
Q

is zolazepam water or lipid soluble?

A

water soluble

25
Q

in what is zolazepam found?

A

telazol: combination NMDA antagonist/benzodiazepine

26
Q

how are benzodiazepines metabolized?

A

primarily liver, pathway differs between drugs
many have active metabolites

27
Q

what is the main metabolite of benzodiazepines in most species?

A

desmethyldiazepam: long half life

28
Q

what are the adverse effects of benzodiazepines?

A

paradoxical excitation
behavioral disinhibition
hepatic necrosis in cats
addiction/physical dependence: dose tapering

29
Q

what are some benzodiazepine antagonists?

A

flumazenil

30
Q

how does flumazenil reverse benzodiazepines?

A

specific competive antagonist wtih high affinity for the benzodiazepine receptor site of the GABAa receptor

31
Q

why are alpha-2-adrenergic receptor agonists popular in veterinary medicine?

A

profound, reliable sedation, analgesia as well as adjunct to anesthesia
easily reversed

32
Q

what receptors do alpha-2-adrenergic receptor agonists have impacts on?

A

alpha-2
also some affinity alpha-1

33
Q

what is the alpha-2 mechanism of action?

A

G-protein coupled receptors located both pre and postsynaptically in the CNS and periphery
extrasynaptically expressed on vascular endothelium of vessels and platelets
4 subtypes: contribute to species differences
sedative effects mediated by presynaptic binding supraspinally in the locus ceruleus of the pons: decreases release of norepinephrine and arousal

34
Q

what is the analgesic effect of alpha-2s mediated by?

A

action in dorsal horn of spinal cord via decreased release of norepinephrine and substance P

35
Q

what do the agonist effects of alpha-2s produce?

A

vasoconstriction in periphery

36
Q

what are the side effects of alpha-2s?

A

bradycardia with biphasic vascular response (vasodilation then vasoconstriction)
centrally mediated reduction in respiration (exaggerated by additive effect of other CNS depressants)

37
Q

what species has serious adverse effects to alpha-2s and what is that effect?

A

sheep
respiratory: activation of pulmonary macrophages that extensively damage the capillary endothelium and alveolar type I cells
intraalveolar hemorrhage/edema, hypoxia, death
not completely reversed by antagonist

38
Q

what are the side effects of alpha-2s other than heart and respiration?

A

musculoskeletal relaxation
emesis (cats mostly)
decrease GI motility
renal diuresis
hyperglycemia
inability to thermoregulate

39
Q

is xylazine specific for alpha-2?

A

no

40
Q

what is medetomidine?

A

racemic mixture of enantiomers (dexmedetomidine and levomedetomidine)

41
Q

what does medetomidine produce?

A

profound reliable sedation and analgesia

42
Q

who is detomidine hydrochloride (dormosedan) used in?

A

horses
bovine
lesser degree small ruminants

43
Q

is detomidine specific?

A

more specific for alpha-2 than xylazine

44
Q

what are alpha-2-adrenergic antagonists used for?

A

to reverse alpha-2 agonists

45
Q

what is the alpha-2-adrenergic antagonist to reverse xylazine?

A

yohimbine

46
Q

what is the alpha-2-adrenergic antagonist to reverse detomidine?

A

tolazoline

47
Q

what is the alpha-2-adrenergic antagonist to reverse demedetomidine and medtomidine?

A

atipamezole (antisedan)

48
Q

what are the side effects of alpha-2-adrenergic antagonists?

A

CNS excitement
yohimbine may cause seizures at high doses
reverses analgesia as well
reversal cardiovascular effect of agonists but hard to predict
reversal respiratory suppression
reversal muscle relaxation and ataxia