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Anaesthesia > Pharmacology of Sedative Drugs > Flashcards

Pharmacology of Sedative Drugs Flashcards

1
Q

Premedication

A

1+ agents given in preparation for an operation, other procedure or txt

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2
Q

Tranquilisation

A

the act to sedate through administration of drugs as the purpose of relieving anxiety & stress

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3
Q

Sedation

A

Act of administration of a sedative agent to produce a state of calm or sleep (deeper state)

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4
Q

Hypnosis

A

Refers to a sleep-like state induced by the administration of certain drugs. A patient may be roused from the effects of hypnotic drugs by stimulation

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5
Q

Narcosis

A

A state of stupor, drowsiness, or unconsciousness produced by certain drugs from which it is NOT easy to rouse the P

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6
Q

What drugs are in the phenothiazine class?

A

Acepromazine, Chlorpromazine, Methotrimeprazine (levopromazine), Prometazine

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7
Q

Outline the pharmacokinetics of Acepromazine

A
  • Admin/absorption: oral & liquid unreliable, iv/im 5-20 mins/30-45 mins
  • Distribution: highly protein bound, crosses BBB
  • Metabolism: extensive liver metabolism
  • Excretion: conjugated & unconjugated metabolites lost in urine
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8
Q

What are the actions of Acepromazine?

A

Antagonises:
* Dopamine receptors for sedative effects
* Histamine receptors for antihistaminic effects
* Cholinergic muscarinic receptors for spasmolytic effects on GIT
* Alpha-1 adrenergic receptors on vessels for vasodilation

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9
Q

What are the CNS pharmacodynamics of Acepromazine?

A
  • Sedation
  • Anti-emesis
  • Extrapyramidal effects at high doses
  • Lowered seizure threshold
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10
Q

What are the GIT pharmacodynamics of Acepromazine?

A
  • Antispasmodic
  • reduced LOS tone
  • increased risk of regurgitation
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11
Q

What are the CVS pharmacodynamics of Acepromazine?

A
  • Hypotension due to vasodilation
  • Anti-arrhythmic
  • Reduction in PCV due to RBC sequestration in spleen causing splenomegaly
  • reduces platelet aggregation
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12
Q

What is a contraindication due to the anti-histaminergic effects of Acepromazine?

A
  • Interference w/ intradermal skin tests
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13
Q

What are the pharmacodynamics of Acepromazine in the reproductive tract?

A
  • Paralysis of retractor-penis muscle

CAUTION IN STALLIONS

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14
Q

When is Acepromazine contraindicated?

A
  • very sick/moribund patients
  • AV block (Boxers, MDR1 dogs)
  • Vasodilation/syncope
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15
Q

What are some key points of overdose with Acepromazine?

A
  • No reversal agent
  • treat symptomatically w/ alpha-1 agonist & BP maintenance
  • Do NOT use adrenaline if BP very low
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16
Q

What drugs are in the alpha-2 agonist class?

A
  • (Dex)medetomidine & detomidine
  • Xylazine
  • Romifidine
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17
Q

Rate the Alpha-2 agonists from least selective for alpha-2 receptors to the most selective.

A
  1. Xylazine (least)
  2. Detomidine
  3. Romifidine
  4. Medetomidine
  5. Dexmedetomidine
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18
Q

What is the mechanism of action of alpha-2 agonists?

A
  • noradrenaline is a natural ligand released & binds to pre & post-synaptic receptors then causing neg FB to stop noradrenaline
  • very stressed/ agitated/ anxious animals may have high circulating noradrenaline in blood, so if given a low dose, it won’t work, but the animal can become overdosed if you keep giving more
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19
Q

Alpha-2 receptors are everywhere in the body so…

A

Caution when using these drugs

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20
Q

What are the centrally mediated effects of alpha-2 agonists?

A
  • sedation
  • analgesia (central/spinal)
  • peripheral vasodilation
  • late bradycardia due to vagal tone
  • emesis in SA
  • reduction of ADH release –> diureis
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21
Q

What are the peripherally mediated effects of alpha-2 agonists?

A
  • vasoconstriction when bound on the receptors –> hypertension, initial bradycardia in response
  • Inhibition of insulin release –> increase in plasma glucose concentration
  • reduction of intestinal mobility –> colic (Eq)
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22
Q

What occurs when you give a bolus of alpha-2 agonists?

A

leads to Vasoconstriction –> BP increases –> increase afterload of the heart and decreases HR –> reduction of CO –> reduction of O2 delivery

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23
Q

What animals can you give Xylazine & in what concentrations?

A
  • Farm Animals 2%
  • Equines 10%
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24
Q

What is the duration of action of Xylazine?

A
  • 30 mins to 1 hour
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25
Q

What are some things to remember about Xylazine in farm animals?

A
  • ruminants are very sensitive to it (lower conc)
  • hypoxaemia & pulmonary oedema in sheep/goats which can be fatal so if you have to give, give IV very slowly
  • can induce labour
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26
Q

What are some key points about Xylazine in equines?

A
  • spasmolytic, analgesic (good for colic)
  • myometrial activity in mares possible
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27
Q

Why is Xylazine NOT used in small animals?

A
  • causes vomiting
  • associated w/ increased anaesthetic mortality
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28
Q

What is the specificity of Xylazine for alpha-2 receptors?

A

160 a-2 receptors : 1 a-1 receptor

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29
Q

What is the specificity of Detomidine for alpha-2 receptors?

A

260 a-2 : 1 a-1

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30
Q

What is the primary way of giving Detomidine?

A

IV

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31
Q

What is the bioavailability of Detomidine if given IM?

A

66-85%

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32
Q

Oral preparations of Detomidine are used in…

A

horses

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33
Q

Detomidine can be used for…

A
  • infusion intra-op
  • standing sedation
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34
Q

Detomidine is not ecbolic. What does this mean & what species is it good for?

A
  • Does not increase contractility of the uterus
  • suitable for use in pregnant cattle, especially if in last trimester
35
Q

Detomidine should not be used w/ what type of drug in horses? Why?

A
  • Potentiated sulphonamides
  • Can cause cardiac arrhythmias
  • Can cause ataxia in horses
36
Q

Detomidine is not suitable in what species?

A

Small animals

37
Q

Romifidine is for what species only?

A

Equines

38
Q

What is the specificity of Romifidine for a-2 receptors?

A

340 a-2 : 1 a-1

39
Q

Out of the alpha-2 agonists, which has the longest duration of action?

A

Romifidine

40
Q

Romifidine causes the least amount of this side effect in horses.

A

Ataxia

41
Q

Romifidine can be used as a CRI intra-op in what species?

A

Horses

42
Q

What is the specificity of (Dex)medetomidine for a-2 receptors?

A

1620 a-2 : 1 a-1

43
Q

What are the names of the racemic mixtures of medetomidine?

A
  • Levomedetomidine
  • Dexmedetomidine
44
Q

What are some side effects of (Dex)medetomidine?

A
  • Profound CVS effects
  • V (uncommon)
  • Nausea if given IM
45
Q

When does (Dex)medetomidine have analgesic properties?

A
  • at high doses
  • acts at shorter duration than sedative effects
  • Esp if given with opioids
46
Q

When should you use alpha-2 agonists?

A
  • When strong sedation or analgesia is required
  • in stable patients only (avoid in heart dz)
  • dysphoric animals, esp coming out of anaesthesia
  • aggressive patients
47
Q

When should you avoid alpha-2 agonists?

A
  • Puppies/kittens
  • Do not combine w/ anticholinergics to correct HR –> can exacerbate BP
48
Q

What are the main alpha-2 ANTagonists?

A
  • Yohimbine
  • Atipamezole
  • Tolazoline
  • Vatinoxan
49
Q

What is important to remember about giving Atipamezole when other drugs aside from an alpha-2 agonist are on board?

A

It will NOT reduce the other medications on board (such as opiates)

50
Q

Atipamezole will reverse what effects of an alpha-2 agonist?

A
  • CV depression
  • Sedation/analgesia
51
Q

Atipamezole should be administered by what route?

A

IM! (IV will wake the animal up too suddenly)

52
Q

What species is Vatinoxan used in for sedation purposes?

A

Dogs only

53
Q

What species can Vatinoxan be a peripheral antagonist?

A

Horses

54
Q

What are the properties of Vatinoxan?

A
  • selective & peripheral A-2 antagonist (does not cross BBB)
  • prevents/minimises early vasoconstriction w/o compromising sedation & analgesia
  • Reduction in duration of time b/c of the effects on the vascular system –> metabolised faster
  • hastens IM absorption of A-2 agonist
55
Q

What are the main benzodiazepines used?

A
  • Midazolam
  • Diazepam
  • Alprazolam
56
Q

What is the mechanism of action of Benzodiazepines?

A
  • enhances affinity of Gaba-alpha receptor for GABA, increasing Cl- conductance to the cell
  • increased Cl- conductance –> hyperpolarisation of post-synaptic membrane –> decreased neuronal transmission

GABA = NT w/i CNS

57
Q

What are the main pharmacodynamic effects of benzodiazepines on the CNS?

A
  • unreliable sedation in animals
  • healthy adults may have agitation
  • synergistic effect w/ other CNS depressants
  • central muscle relaxant
  • anticonvulsant, decrease in ICP
  • amnesia
  • appetite stimulation in cats
58
Q

What are the main pharmacodynamic effects of benzodiazepines in CVS?

A
  • Midazolam: reduced inotropy, mild vasodilation at high doses
  • very safe w/i normal ranges
  • may potentiate resp depression of other drugs, but doesn’t cause on its own
59
Q

What are the main pharmacodynamic effects of benzodiazepines on the respiratory system?

A
  • minimal depression
  • might potentiate respiratory depression of other agents
60
Q

What are some things to note about benzodiazepines?

A
  • use in very young or old or sick patients, NOT in healthy patients
  • no analgesia!
61
Q

What are the pharmacokinetics of benzodiazepines?

A
  • 95-99% protein bound, dose reduction in hypoproteinaemic patients
  • metabolised in liver (caution in liver P’s)
62
Q

Diazepam is solubilised in… which can make it very … in texture

A
  1. propylene glycol
  2. oily
63
Q

Diazepam should only be given by what route of administration? Why?

A
  • IV
  • IM has erratic absorption and can cause pain
64
Q

How fast is the onset of action of Diazepam when given IV?

A

Rapid

65
Q

Diazepam is highly…

A

lipid soluble & protein bound

66
Q

Diazepam is metabolised in the…

A

liver in CYP450 isoforms (CYP2DP, CYP3A4)

67
Q

What is the active metabolite of Diazepam? What are its properties?

A

Nordiazepam
Has long T1/2 & can cross the placenta

68
Q

Metabolism of diazepam is inhibited by…

A

microsomal enzyme inhibitors (Cimetidine, erythromycin, omeprazole)

69
Q

Midazolam use in vet med is considered…

A

Off-label

70
Q

Midazolam is water soluble if the pH is…

A

< 4

71
Q

Midazolam is lipid soluble at… causing it to have a … onset

A

body pH
fast onset

72
Q

What routes can midazolam be given?

A

IV/IM/SQ/intranasal

73
Q

What is the duration of action of midazolam?

A

1-2 hours

74
Q

Midazolam has how many active metabolites?

A

2

75
Q

Midazolam should be used with caution in what patients? Why?

A
  • liver issues
  • inhibits CYP450 which reduces hepatic clearance and can increase the duration of action
76
Q

Which is more suitable for CRI: diazepam or midazolam?

A

Midazolam

77
Q

Acute overdose/toxicity of benzodiazepines can cause…

A

long-lasting sedation, CNS depression, coma

78
Q

What is the antagonist for benzodiazepines?

A

Flumazenil

79
Q

What is the main drug of importance in the butyrophenones? What animal is it used in?

A

Azaperone
Pigs only

80
Q

What are some things to note about Azaperone use in pigs?

A
  • onset: up to 30 min after IM inj
  • DO NOT DISTURB AFTER INJ
  • lasts 2-4 hrs
  • distribution: large
  • metabolism: liver
  • Excretion: faeces, urine
  • NO REVERSAL AGENT!
81
Q

What are the main cardiovascular effects of butyrophenones?

A
  • A-1 receptor blockade may cause hypotenion
  • Antiarrhythmic
  • May protect against catecholamine induced arrhythmias
82
Q

What are the main CNS effects of butyrophenones?

A

Anti-emetic via action at CTZ
Dopamine antagonist –> sedation

83
Q

What other non-specific signs can appear with butyrophenones?

A
  • transient salivation, piling, panting, shivering in pigs
  • NO analgesia
  • paradoxical excitement in horses <– don’t give to a horse dumbass

Anaesthesia (23 decks)

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