Adrenergic Receptor agonists

Question 1

Name some effects of activation of alpha-2 receptors.

Answer 1

• platelet aggregation
• inhibition of NE release (autoreceptor)
• vascular smooth muscle contraction
• inhibition of renin release
• inhibition of lipolysis

Question 2

What are the effects of stimulation of beta-1 receptors?

Answer 2

• increases force and rate of contraction (note: increased contractility is how CO is increased not HR)
• increases release of renin

Question 3

What are the effects of beta-2 receptor activation?

Answer 3

• smooth muscle relaxation (resp, uterine, vascular)
• promotes potassium uptake by skeletal muscle
• glycogenolysis (liver)

Question 4

alpha-1 agonist that acts as a mydriatic and decongestant

increases bp

Answer 4

phenylephrine

Question 5

What are the effects of alpha-1 receptor stimulation?

Answer 5

• contraction of most vascular innervated smooth muscle-> increased vascular resistance
• pupillary dilation (mydriasis)
• pilomotor smooth muscle -> makes hair stand up
• prostate smooth muscle contraction

Question 6

alpha-1 agonist used to treat orthostatic hypotension

Answer 6

midodrine, ephedrine, methoxamine (also used for hypotension associated with spinal anesthesia)

Question 7

alpha-2 receptors agonist that causes vasoconstriction when given IV
-decreases bp by actions of the CNS
Adverse: sedation
-in order to avoid hypertensive crisis with withdrawal of this medication, give a beta-blocker
-do not give in depression
Interactions: TCAs (why do you not give with these?)

Answer 7

clonidine

TCAs inhibit NET and SERT -> hypertensive crisis

Question 8

-alpha-2 receptor agonist that decreases bp through actions of the CNS (inhibition of NE release)
-safe for treatment of HTN in pregnancy
Adverse: sedation, nightmares, depression, vertigo, lactation in both men & women
-causes positive Coombs test

Answer 8

methyldopa

Question 9

other alpha-2 agonists used to treat HTN -> via CNS action

Answer 9

guanfacine
guanabenz
moxonidine
rimenidine
oxymetazoline

Question 10

How do indirect alpha adrenergic agonists cause their effect?

Answer 10

-displace stored catecholamines from the nerve ending
-inhibit reuptake or metabolism of NE
Ex: MAOIs and tyramine (displaces NT-> acts like NE)

Question 11

Indirect-acting alpha agonists

Answer 11

atomoxetine -> non stimulant tx for ADHD
reboxetine
sibutramine
cocaine

Question 12

What are the effects of NE?

Answer 12

Agonist of alpha-1, alpha-2, beta-1 and little effect on beta-2
-increases PVR
-increases both systolic and diastolic bp
-positive inotrope (beta-1)
-increases HR (beta-1)
increased HR and contractility causes baroreflex decrease in bp

Question 13

What are the effects of epinephrine?

Answer 13

• potent vasoconstrictor (alpha-1)
• increased HR and contractility (beta-1)
• bronchodilation (beta-2)
• skeletal muscle vasodilation (beta-2)
• promotes uptake of potassium and leads to decreased extracellular potassium

Question 14

What are the effects isoproterenol?

Answer 14

• potent beta receptor agonist
• increases HR and contractility (beta-1) -> increased calcium influx increases conduction velocity and contractility
• potent vasodilator (beta-2)
• have a marked increase in CO with decrease in diastolic and MAP

Question 15

beta-2 agonist that is a bronchodilator and used to treat asthma

Answer 15

albuterol

salmeterol -> long-acting partial agonist of beta-2

Question 16

beta-1 agonist with action at alpha-1 and alpha-2

• used to increase CO
• used in cardiogenic shock because it has a greater inotropic than chronotropic effect compared to isoproterenol

Answer 16

dobutamine

also used for cardiac stress test in patients who cannot tolerate exercise