Ch.19: Sedatives and Tranquilizers (Pablo) Flashcards by Sara Prent

Name 3 phenothiazines

acepromazine
promazine
chlorpromazine

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Phenothiazine mech. of action

inhibit DA receptors in CNS–> sedation and tranquilization
block NE at alpha-adrenergic receptors in periphery

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What kind of receptors are DA receptors?

G-protein coupled

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phenothiazine indications

sedation/tranquil.

- prevention of nausea and vomiting

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other phenothiazine PK effects

may see rigidity with high doses
may lower seizure threshold***
peripheral vasodilation
splenic engorgement
decreased afterload
low effect on motor activity

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Why is Ace not safe for Boxers?

can result in bradycardia dn hypertension

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Important contraindication for Ace***

can lower seizure threshold

-caution with horses and boxers

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primary use of chlorpromazine

antiemetic in D/C

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Ace available in what admin routes?

IV, IM, SC, oral

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phenothiazines have low/high therapeutic index

very high when used in NONanesthetized animals (lowered during anesthesia)

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contraindicatons of phenothiazines

dehydration
hypovolemia (dec. blood volume)
bleeding
coagulopathies
shock

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3 major effects of alpha-2 agonists***

sedation
analgesia
master relaxation

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basic structure of alpha-2 agonists

benzene ring with imidazole ring (exception = xylazine, which has a benzene + thiazole ring)

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Name 6 alpha-2 agonists

xylazine
detomidine
medetomidine
dexmedetomidine
romifidine
clonidine

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most arrhythmogenic a2 agonist?**

xylazine (due to presence of thiazole ring)

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mech. of action of a2 agonists (3 main parts)

mimic the action of NE, therefore inhibiting further release of NE –> sedation
also stimulates a1 receptor, which can result in adverse effects
imidazoline receptor stimulation –> mediates hyptoension, antiarrhythmogenesis. Not involved in sedation

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notable feature of promazine

similar to acepromazine. popular use as oral med

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Why do you want a2 agonist with high a2 selectivity and low a1 stimulation (high a2:a1 ratio)

will be more selective for sedation/analgesic effects and less adverse effects

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Xylazine has high/low a2:a1 ratio***

low! It is the least potent and has more neg. side effects

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most specific alpha-2 agonist that we use***

dexmedetomidine (even though medetomidine is even more specific)

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Does xylazine have imidazoline receptor stimulation activity?

No, b/c it doesn’t have an imidazole ring

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Indications for alpha-2 agonists

sedation
chem. restraint
preanesthetic
analgesia
emesis

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CNS effects of alpha-2 agonists

profound sedation via locus coeruleus stim.
paradoxical excitement possible in less specific a2 agonists
anesthetic sparing effect

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CV effects of alpha-2 agonists***

-biphasic response:
Phase 1:
-activation of central a2 receptors –> dec. sympathetic outflow, inc. parasym. tone.
-activation of peripheral a1 and a2 receptors –> vasoconstriction, hypertension, reflex bradycardia
Phase2:
-dec. HR and BP (due to dec. NE), dec. cardiac output
(May see 2nd degree AV block)

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effect of combining a2 agonist with anticholinergic agent

- increased risk of dysrhythmia - hypertension - cardiac output not normalized

Respiratory effects of alpha-2 agonists

- mild resp. depression | - cyanosis

xylazine in sheep

- can result in pulmonary edema and hypoxemia | - pulmonary macrophage activation --> damage endothelium

Musculoskeletal effects of alpha-2 agonists

- muscle relax | - twitch possible if given IV

Gastrointestinal effects of a2 agonits

- xylazine: vomiting | - reduced GI motility, acid secretion

Renal effects of a2 agonists

- diuresis (inhibit ADH, inc. Na excretion) - dec. renin - dec. bladder capacity

endocrine effects of a2 agonists

- dec. catecholamine lvls | - dec. stress response

metabolic effects of a2 agonists

-hyperglycemia (due to decreased insulin release)

Repro effects of a2 agonists

xylazine: premature parturition in cows myometrial contraction in non-gravid uterus decreased myometrial contraction at low doses only

thermoregulation effects of a2 agonists

-dec. body temp

a2 agonists help/hurt equine recovery from inhalation anesthesia

help

a2 agonists and analgesia

-profound analgesia

first a2 agonist used in vet med

xylazine

which animals are sensitive to sedative effects of xylazine?

cattle, ruminants

Why do different species have different sensitivity to xylazine

differences in G-protein signaling pathways

important chars. of detomidine*

- approved in horses** - longest duration of action** - higher a2:a1 ratio than xylazine

important chars. of medetomidine*

- can be used to tx emergence delirium in SA following anesthesia** - provides sedation, anxiolysis, analgesia

important chars. of dexmedetomidine

-similar to medetomidine, but w/ higher HR/CO

chars. of Romifidine*

- produces less ataxia in horses than xylazine** | - longer duration of sedation than xylazine

chars. of clonidine*

- older human agent** | - not used in vet med

adverse effects of a2 agonists

- sudden arousal from sedation - vomiting - hyperglycemia - diuresis

contraindications of a2 agonists

poor CO

3 a2 antagonists

tolazole yohimbine atipamezole

a2 antag. mech. of action

-REVERSAL of sedation, anxiolysis, analgesia, CV changes induced by a2 agonists

yohimbine best reverses which drug?**

xylazine

atipamezole best reverses which drug?**

dexmedetomidine and medetomidine

tolazoline reverses what?*

xylazine in cattle and SR

list yohimbine, tolazoline, and atipamezole in order of increasing selectiving for a2 receptors

tolazoline < yohimbine < atipamezole

adverse effects of a2 antagonists

- CNS excitement - vasodilation - tachycardia - CV collapse - delirium, aggression

Benzodiazepine mech. of action

-enhance GABA receptor --> Cl channel opening --> hyperpolarization --> sedation

indications of benzos*

- preanesthetic - anticonvulsant - m. relaxant - phobia

CNS effects of benzos*

- paradoxical excitement** - dec. cerebral blood flow/O2 consumption - anticonvulsant

CV effects of benzos*

- minimal CV depression at clinical doses** | - high doses --> dec. MAP, inc. CO

Resp. effects of benzos*

-mild resp. depression

MS effects of benzos

- m. relax - ataxia - can cause agitation in horses

T/F: benzodiazepines can cause pain on admin*

T (due to propylene glycol vehicle)

Do benzos cause analgesia?

Diazepam vs. midazolam***

- diazepam is lipid soluble, short duration of action, w/ unpredictable absorption IM or SC, can be given rectally. - midazolam has ~2x potency of diazepam***, is water soluble due to presence of imidazole ring**, has reliable bioavailability IM, IV, SC, has faster onset, and can be given nasally.

potency and duration of lorazepam vs. diazepam

lorazepam 10x more potent, and longer duration of action than diazepam

chars. of zolazepam*

- similar to diazepam - only used in combo with tiletamine - cats recover slower and calmer than dogs

benzo adverse effects

- agitation, vocalization, aggression - hepatic failure in cats following repeated oral admin. - abstinence syndrome (tremors, etc.) w/ sudden stoppage of tx

signs of benzo overdose

- ataxia - depression - agitation - GI upset - weakness - tremors - vocal - tachycardia/pnea - hypothermia

benzo antagonist drug

flumazenil

flumazenil mech. of action

-competitively antagonizes benzos on GABA receptor --> prevents hyperpolarization of postsynaptic memb.

PD Effects of flumazenil

- reverses electroencephalographic changes of benzos - inc. BP - inc. minute vent. and tidal volume

flumazenil adverse effects

- seizure in chronically tx benzo patients - reduced activity in patients w/o benzo - inflamm./necrosis when administered perivascularly - dysrrhythmia

name 2 butyrophenone derivs

azaperone and droperidol

butyrophenone derivates mech. of action

-neuroleptic effect due to antagonism of D-2 receptors

Only FDA drug for sedation in pigs***

azaperone

indications for droperidol use

- antiemetic | - preanesthetic med

PD effects of butyrophenone derivs

-dec. HR, CO -dec. Hb due to splenic sequestration of RBCs -dec. m. tone NO ANALGESIA**

T/F: droperidol used to be in combo with fentanyl

T (due to aggressive behavior)

Ch.19: Sedatives and Tranquilizers (Pablo) Flashcards

(76 cards)