Alpha 2 agonists Flashcards
What pathways do alpha-2 agonists affect?
perception, modulation, and transmission.
Why is sedation so effective with alpha 2 agonists?
because of a decrease in norepi release
What is the competitive antagonist for dexmedetomidine?
atipamezole
What is the competitive antagonist for xylazene?
yohimbine
What are the sedative and analgesic effects of alpha 2 agonists?
they have competitive agonism for alpha-2 receptors in the sensory cortex of the brain, causing sedation. The alpha 2 receptors in the spinal cord cause analgesia and muscle relaxation.
What are the autonomic nervous system effects of alpha 2 agonists?
cause vasoconstriction
Which is the most specific alpha 2 agonist?
dexmedetomidine
Which is the least specific alpha 2 agonist?
xylazine
What are the most common routes of administration of alpha 2 agonists?
IV or IM.
T/F: alpha 2 agonists don’t cross the BBB
False.
What is the emetic of choice for use in cats?
xylazine
T/F: the cardiovascular effects of alpha 2 agonists are bi-phasic.
True.
What is phase I when using alpha 2 agonists likely to cause?
peripheral vasoconstriction, which will increase systemic vascular resistance and cause a transient increase in mean arterial blood pressure, causing reflex bradycardia. The heart rate will drop to maintain constant cerebral perfusion pressure.
What receptors mediate phase I?
alpha 1 receptors
What receptors mediate phase II? What is the result of phase 2?
alpha 2 receptors mediate it. There is peripheral vasodilation, decrease in norepi, and the heart rate stays low. Can lead to hypotension and bradycardia.
By what percentage can cardiac output decrease with alpha 2 agonists?
30-50%
When should you treat decreased heart rate and what do you do to treat it?
Treat when the patient becomes cardiovascularly unstable. You can reverse or give an anti-cholinergic if the P is in sx.
What is the most common bradyarrhythmia to occur with alpha 2 agonists?
second degree incomplete AV block
What causes decreased cardiac output when using alpha 2 agonists?
increase BP and reflex bradycardia.
What effect do alpha 2 agonists have on the respiratory system?
decrease in resp rate and mild resp. depression. In sheep, goats, and horses you will see an increase resp. rate, airway pressures, and pulmonary resistance. These changes can lead to hypoxemia or pulmonary edema.
Do alpha 2 agonists have a diuretic effect?
Yes. they reduce ADH release and its function.
In what animals may these drugs cause abortion in?
In ruminants, due to myometrial contractions.
What are the clinical uses of alpha 2 agonists?
sedation (dose dependent, NOT anesthesia), pre-anesthetic, analgesia**, emetic, behavioral, and chemical ejaculation in horses.
**=important
What 2 drugs should you not use with alpha 2 agonists?
epinephrine and atropine.
When are alpha 2 agonists contraindicated?
in critically ill patients and patients with shock.
How should the reversal agents for alpha 2 agonists be administered?
IM. Administering it IV can cause cardiovascular collapse.
Will alpha-2 antagonists reverse both sedative and analgesic effects?
Yes.
