Alpha 2 agonists and antagonists

Question 1

Name the alpha 2 agonists

Answer 1

1. Dexmedetomidine (Dexdom)
2. Xylazine

Question 2

Name the alpha 2 antagonists

Answer 2

1. Atipamezole
2. Yohimbine

Question 3

____________ is a mixed A2 agonist/antagonist

Answer 3

Medetomidine / Vatinoxan (Zenalpha)

Question 4

Which parts of the pain pathway do A2 agonists act on?

Answer 4

1. Transmission
2. Modulation
3. Perception

Question 5

Xylazine is approved for use in __________

Answer 5

Horse, deer, elk

Question 6

Dexmedetomidine is approved for us in __________

Answer 6

Dogs, cats, exotics

Question 7

Which species is most sensitive to xylazine?

Answer 7

Cows

Question 8

Why is xylazine not frequently used in small animals?

Answer 8

More potent than dexdom, increased morbidity

Question 9

What is the overall clinical effect of A2 agonists?

Answer 9

Sedation and analgesia

Question 10

Which A2 agonist is more selective to A2?

Answer 10

Dexmedetomidine

less A1 effects

Question 11

How are A2 agonists commonly given?

Answer 11

IV or IM

Question 12

Why are A2 agonists not given SQ?

Answer 12

Poor absorption due to local vasoconstriction (some a1 effects)

Question 13

Which A2 agonist has a longer duration of action?

Answer 13

Dexmedetomidine > xylazine

Question 14

What is the clinical indications for use of xylazine in cats?

Answer 14

Emetic of choice for cats to induce vomiting

stimulation of A2 receptors in the emetic center and CRTZ

Question 15

What occurs in phase I when using A2 agonists?

Answer 15

Phase I - Peripheral phase

• Peripheral vasoconstriction mediated by a1 receptors
• Causes reflex bradycardia and INC. systemic BP

dont give anticholinergics (Atropine, Glycopyrrolate) during Phase I

Question 16

What occurs in phase II when using A2 agonists?

Answer 16

Phase II - Central phase

• Decreased sympathetic tone (Dec NE)
• HR stays low
• Peripheral vasodilation leading to hypotension and bradycardia

CO can decrease 30-50% with A2 agonists

Question 17

What is the most common arrhythmia seen with A2 agonists?

Answer 17

2 degree AV block

Question 18

What does a biphasic effect mean in regards to A2 agonists?

Answer 18

Initial vasoconstriction and hypertension followed by vasodilation and hypotension due to CNS depression

Question 19

What might happen to BP if you give atropine for reflex bradycardia?

Answer 19

Hypertension and increased afterload (not good)

Question 20

___________ is a specific competitive antagonist for dexmedetomidine

Answer 20

Atipamezole (Antisedan)

Question 21

___________ is a specific competitive antagonist for yohimbine

Answer 21

Xylazine

Question 22

You want to reverse the effects of an A2 agonist, what route of admin would you give the reversal?

Answer 22

IM

More side effects when given IV like CV collapse

Question 23

Effect of A2 agonists on GI motility?

Answer 23

Decreases GI motility

Emetic of choice in cats

Question 24

Effects of A2 agonists on the uterus?

Answer 24

Stimulates myometrial contractions, risk for abortions

Question 25

Effects of A2 agonists on the kidneys?

Answer 25

Mild diuresis (PU) by reducing ADH release

Question 26

What can be high on a biochem panel when using A2 agonists?

Answer 26

Glucose (hyperglycemia) Due to decrease release of insulin **more pronounced in horses and ruminants** **be careful using A2 agonists on diabetic patients**

Question 27

Which metabolic condition would be a precaution when selecting an A2 agonist?

Answer 27

Diabetes **A2 decreases insulin resulting in hyperglycemia**

Question 28

A2 agonists can cause _________ (hypothermia/hyperthermia)

Answer 28

Hypothermia (low temp) due to vasoconstriction

Question 29

What precaution must be taken when using A2 agonists on deer?

Answer 29

Delayed hypersensitivity rxn

Question 30

A2 agonists should not be used concurrently with ____________

Answer 30

Epinephrine and atropine

Question 31

__________ is the most selective A2 antagonist

Answer 31

Atipamezole (Antisedan)

Question 32

What GI side effects can be seen after administration of Atipamezole?

Answer 32

Mild salivation and diarrhea (A2 antagonist - Reversal agent)

Question 33

What side effects can be seen if an A2 antagonist is given without an A2 agonist?

Answer 33

CNS excitement, tachycardia and hypotension due to vasodilation

Question 34

Why might Medetomidine/Vatinoxan (ZenAlpha) be used over other A2 agonists?

Answer 34

Faster onset, shorter duration - can still be reversed with Atipamezole - less CV depression (less hypotension) **good for outpatient procedures**

Question 35

Medetomidine/Vatinoxan (ZenAlpha) precautions?

Answer 35

Beware of hypotension in cats and horses

Question 36

Other therapeutic uses for A2 agonists?

Answer 36

Mitoban toxicity, Amitraz tick collar toxicity

Question 37

A2 agonists can be used in horses for?

Answer 37

Chemical ejaculation