Alpha 2 Agents

Question 1

list the therapeutic benefits of Alpha 2 agonists:

Answer 1

sedation, analgesia, skeletal muscle relaxation

Question 2

What are the major effects of xylazine on cadiovascular system?

Answer 2

Phase-1
activate peripheral alpha 2 receptors, rapid incrase in SVR, increases arterial BP

Phase 2
hypertension- baroreceptor mediated bradycardia
over time peripheral effects subside and the BP will return to normal

Question 3

What are the major effects of xylazine on Gi/emesis

Answer 3

used in horses for tx colic associated pain

emesis frequently in cats; less often in dogs

Question 4

What are the major effects of xylazine on renal?

Answer 4

increase in urine output onbserve transiently due to supression of ADH release centrally

Question 5

What are the major effects of xylazine on uterine?

Answer 5

oxytocin like effect, dont give to cows in last trimester- abortion

Question 6

What are the major effects of xylazine on respiratory?

Answer 6

minor hypoxia in cattle and sheep

activation of peripheral alpha-2 adrenoreceptors, leads to increase airway resistance

Question 7

Adverse effects of xylazine:

Answer 7

synergistic actions with phenothiazines
additive effects w. CNS depressants
decrease plasma insulin levels (hyperglycemia/glycosuria)
RMTs are more sensitive to xylazine than dogs. horses, cat

Question 8

What is the major clinical application of Yohimbine?

Answer 8

reversal agent for xylazine

adverse effect- CNS excitement, muscle tremors, salivation

Question 9

What is the major clinical application of Atipamezole?

Answer 9

highly selective for reversal of medotomidine in dogs

Question 10

What is the major clinical application of Tolazoline?

Answer 10

least selective antagonist

Question 11

What drug is most selective for alpha 2 : alpha 1`

Answer 11

Medetomidine

Question 12

What drug is least selective for alpha 2: alpha 1

Answer 12

Xylazine

Question 13

What is the active enantiomer of medetomine?

Answer 13

dexmedetomine, the other is levomedetomidine`

Question 14

Alpha 2 agonist mech of action

Answer 14

activation of presynaptic alpha 2 receptors in CNS/PNS
AND
post junctional alpha 2

results in decrease in sympathetic outflow

decrease in catecholamines

sedation, analgesia, and skeletal muscle relaxation

Question 15

Where are the receptors that mediate sedation via alpha 2 agonists?

Answer 15

primarily in the locus coeruleus on the pons and lower brain stem- block NE release

Question 16

What species is the most sensitive to alpha 2 agonism?

Answer 16

RMTs > cats/dogs > pigs

Question 17

What is the mech of analgesia w/ regards to alpha 2 agonism?

Answer 17

pain modulation starts in the brain and SC
SC is site where nociceptive fibers synapse
both post/pre-synaptic inhibitory effects are responsible for the anti-nociceptive action
mediated by inhibition of inter neuronal transmission in SC