Mechanism of Action

Question 1

guanethidine

Answer 1

Enters presynaptic nerve terminal via NET and enters and fills vesicles, blocking NE from entering vesicle.

NE metabolized by MAO instead of released.

Decrease BP.

Question 2

reserpine

Answer 2

Enters presynaptic nerve terminal directly, binds at VMAT to prevent NE from entering vesicle.

Empty vesicles. NE metabolized by MAO instead of released.

Decrease BP

Question 3

amphetamine

Answer 3

Substrate for NET, enters terminal and knocks NE out of the vesicle, increasing synaptic NE. (“Facilitated Exchange Diffusion”)

Increase BP and HR.

Question 4

Tyramine

Answer 4

Enters via NET if it escapes the MAO in the gut (pt is on MAOI). Displaces NE from vesicles.

Hypertensive crisis.

Question 5

cocaine

Answer 5

Blocks NET, increasing synaptic NE.

Increase BP and HR.

Question 6

phenylephrine

Answer 6

alpha 1 agonist

nasal decongestant

Question 7

isoproterenol

Answer 7

beta 1 agonist

increase HR, contractility

Question 8

phentolamine

Answer 8

alpha blocker

Question 9

propranolol

Answer 9

beta blocker

antihypertensive

Question 10

xanthines (caffeine, theophylline)

Answer 10

inhibit phosphodiesterase (which would inactivate cAMP)
cerebral blood vessels constricted
bronchi dilated

antagonist at adenosine = prevent sleepiness

cross BBB

do not bind to beta receptors