Sedatives and Tranquilizers

Question 1

phenothiazines

Answer 1

• dopaminergic antagonist: sedation and tranquilization
• alpha antagonist: peripheral vasodilation

Question 2

acepromazine maleate

Answer 2

• phenothiazine
• potent sedative and anxiolytic
• anti-emetic
• anti-arrhythmic properties
• decreases dose of other drugs
• enhances analgesia of opioids

Question 3

side effects of ace

Answer 3

• myocardial contractility depression
• vascular smooth muscle relaxation
  
  • decrease BP and vasomotor reflex -> vasodilation -> decrease afterload (good)
• persistent or permanent penile paralysis in horses
• affects platelet aggregation

Question 4

Ace and Boxers

Answer 4

• some Boxers seem to have exaggerated response to Ace: very sedated and severely hypotensive

Question 5

contraindications for Ace

Answer 5

• hypotension/hypovolemia
• decreased myocardial contractility (DCM)
• coagulopathies
• liver and renal diseases?
  
  • decrease BP, decrease damage to kidney and increase perfusion (need to maintain BP)
• seizures?

Question 6

promazine

Answer 6

• phenothiazine (old anti-psychotic)
• similar to Ace
• injectable and granules

Question 7

benzodiazepines

Answer 7

• act on alpha 1, 2 and gamma subunit of GABAA channel
• sedation
• anxiolysis
• muscle relaxation
• anti-convulsive
• anterograde amnesia
• potentially can decrease induction agent requirements

Question 8

diazepam

Answer 8

• benzodiazepine
• highly lipid soluble
• rapidly crosses BBB and placental barrier
• minimal CV effects
• half-life 2.5 to 6 hours
• viscous and light sensitive, binds to plastic

Question 9

metabolism of diazepam

Answer 9

• hepatic metabolism
• two active metabolites (dogs and cats)
  
  • nordiazepam and oxazepam
• horse urinates metabolites out immediately (not active)

Question 10

midazolam

Answer 10

• benzodiazepine
• water soluble due to imidazole ring
  
  • mixes well with other drugs
• can be given IM
• more potent but shorter acting than diazepam
• similar effects to Diazepam
• crosses BBB and placental barrier

Question 11

zolazepam

Answer 11

• benzodiazepine
• anticonvulsant and muscle relaxant
• only available in combo with tiletamine (Telazol)
  
  • most potent benzo in vet med

Question 12

flumazenil

Answer 12

• benzodiazepine competitive antagonist
• very weak agonist effect (no anxiety with reversal)
• used for competitive reversal of benzo agonists

Question 13

alpha₂-adrenergic agonists

Answer 13

• act on pre-synaptic alpha₂ receptor in sympathetic system
  
  • decrease in NE release: sedation, muscle relaxation, vasodilation, pre-synaptic bradycardia
• also acts on alpha₂ receptors postsynaptically
  
  • mimics NE and EPI: vasoconstrtion and post-synaptic bradycardia

Question 14

effects of alpha₂-adrenergic agonists

Answer 14

• anxiolytic
• sedative and muscle relaxant
• analgesia
• decreased ADH release
• decreased insulin release
• hypertension followed by hypotension
• reflex bradycardia

Question 15

cardiovascular effects of alpha₂-adrenergic agonists

Answer 15

• decrease HR
  
  • hypertension and decrease sympathetic tone
• decrease CO
  
  • decrease mycocardial contractily and decrease HR
• increase and then decrease BP

Question 16

xylazine

Answer 16

• alpha₂ agonist (less selective)
• more ataxia
• shorter duration
• can cause vomiting in dogs and cats

Question 17

detomidine

Answer 17

• alpha₂ agonist (still not very selective)
• profound sedation
• ataxia
• longest duration of action
• approved for use in horses

Question 18

romifidine

Answer 18

• alpha₂-agonist (not very selective)
• good sedation, some muscle relaxant
• less ataxia
• may improve quality of recovery in horses
  
  • adult horses only
• longer duration of sedation than xylazine

Question 19

dexmedetomidine

Answer 19

• alpha₂-agonist (most selective)
• profound sedation
• higher HR and CO than with medetomidine
• may need to intubate some dogs

Question 20

tolazoline

Answer 20

• non-selective alpha antagonist
• acts also on I₂-Imidazoline receptors
• competitive reversal of alpha₂ agonists
  
  • reverses xylazine in cattle and small ruminants
• histaminergic antagonistic activity
• ineffective in captive bears…

Question 21

atipamizole

Answer 21

• alpha₂ antagonist (highly specific)
• used to reverse dexmedetomidine and medetomidine in dogs, cats, and exotic species
• IM or SC

Question 22

yohimbine

Answer 22

• non-selective alpha antagonist
• most commonly used to reverse xylazine
• give only SC or IM
• can causes seizures at high doses