Premedication 2 - A2 Agonists and Phenothiazines

Question 1

What group of drugs are the strongest available sedatives?
A) benzodiazepines
B) anticholinergics
C) opioids
D) alpha 2 agonists

Answer 1

D - alpha 2 agonists

Question 2

3 locations that alpha 2 agonists act at

Answer 2

presynaptic membrane (CNS)
post-synaptic membrane (vascular smooth muscle)
extra-synaptic sites (pancreas, adipocytes, etc)

Question 3

Activation of the alpha 2 receptors in the walls of arteries and veins causes _______.

Answer 3

vasoconstriction (is also most concerning side effect of alpha agonists)

Question 4

T/F: alpha 2 agonism on adipocytes results in inhibition of lipolysis

Answer 4

True

Question 5

Alpha 2 agonism on pancreatic B cells causes inhibition of insulin release, resulting in _______.

Answer 5

hyperglycaemia

Question 6

List the CNS effects of alpha 2 agonists

Answer 6

sedation
analgesia
muscle relaxation

Question 7

2 important cardiovascular effects of alpha 2 agonists

Answer 7

vasoconstriction and reflex bradycardia –> results in low CO and tissue perfusion

Question 8

Would you use alpha 2 agonists in a hemodynamically unstable patient?

Answer 8

No due to CV effects

Question 9

Respiratory effects of alpha 2 agonists

Answer 9

mild resp depression
RR decrease but tidal volume increases
upper airway resistance
V/Q mismatch

Question 10

Xylazine is contraindicated in which species?
A) Cats
B) Horses
C) Sheep
D) Cows

Answer 10

C - Sheep because see hypoxemia and lung edema

Question 11

Xylazine likely causes vomiting in:
A) Dogs
B) Cats
C) Guinea pigs
D) Horses

Answer 11

B - cats

Question 12

Xylazine may cause uterine contractions and abortions in:
A) goats
B) cows
C) horses
D0 sheep

Answer 12

B - cows

Question 13

Indications for use of alpha 2 agonist

Answer 13

sedation aggressive animals, sedation in the ICU, sedation to manage post-op airway obstruction

Question 14

T/F: alpha 2 agonists are safe for most risk patients

Answer 14

False

Question 15

Which is the best option for antagonizing alpha agonist?
A) atipamezole
B) yohimbe
C) tolazoline
C) Detomidine

Answer 15

A - atipamezole

Question 16

T/F: always give alpha2 antagonists IM

Answer 16

true

Question 17

Number one choice of premedication for horses is

Answer 17

Xylazine

Question 18

The most specific drug for alpha 2 receptors is

Answer 18

Dexmedetomidine

Question 19

Which alpha 2 agonist is preferred for standing dental surgery in horses?

Answer 19

Romifidine

Question 20

Which receptors does Acepromazine antagonize?

Answer 20

dopamine, serotonin, alpha 1, histamine

Question 21

What is an important phenothiazine?

Answer 21

Acepromazine

Question 22

CNS effects of Acepromazine?

Answer 22

weak sedation, antiemetic, no analgesic effect

Question 23

CV effects of phenothiazines

Answer 23

antagonist on alpha1 = vasodilation and hypotension

may cause death of hypovolemic patients

Question 24

Phenothiazine effects on stallions

Answer 24

penile prolapse

Question 25

Indications for phenothiazine use (acepromazine)

Answer 25

mild sedation for premed or post op
prevention/treatment of opioid dysphoria
prevention of emesis causes by morphine
sedation of dogs with laryngeal paralysis
enhance sedative effects of xylazine in horses

Question 26

Contraindications of phenothiazine use

Answer 26

hypovolemia, hemodynamic instability
very young or old patients
Von-willebrand disease (Dobes)
boxers may be sensitive (bradycardia)
breeding stallions (penile prolapse)

Question 27

Describe butyrophenones

Answer 27

similar to phenothiazines
droperidol and azaperone
sedative effect similar to ACE
more likely to cause behavioural side effects
less hypotensive and stronger antiemetic
less effects on platelet

Question 28

T/F: ACE inhibits platelet function

Answer 28

true