Alpha-blockers

Question 1

Epinephrine acts on which receptors?

Answer 1

Alpha-1 = Alpha-2
Beta-1 = Beta2*

Question 2

Low doses of epinephrine vs high doses of epinephrine’s effect on cardiac stimulation

Answer 2

@low doses: Cardiac-stimulant affect predominates

@High Doses: Vasoconstrictor effect predominates

Question 3

Norepinephrine acts on which receptors?

Answer 3

Alpha-1
Alpha-2
Beta-1

Question 4

Isoproternol acts on what receptors?

Answer 4

Beta-1 and Beta-2 equally

Question 5

Doxazosin

Answer 5

Selective Alpha-blocker
*Alpha-1

Deceases BP and BPH

Question 6

Non-specific Alpha-blockers and their adverse affects

Answer 6

1. Phenoxybenzamine - Sinus tach. and nasal congestion
   (other: Drowsiness, fatigue, confusion, headache, xerostomia (dry mouth) and ejactulation probz)
2. Phentolamine - Orthostatic hypotension, reflex tachycardia -> cardiac arrhythmias

Question 7

Terazosin

Answer 7

Selective Alpha-blocker
*Alpha-1

Deceases BP and BPH

Question 8

Phenoxybenzamine

Answer 8

Non-competitive (COVALENT) Alpha-1 and Alpha 2 receptor blocker
(Alpha-1 > Alpha-2)
Non-specific

Reduces BP via vasodilation (less effective than specifc alpha-1 blockers)

used to tx: Pheochromoctoma, Raynauds, frostbite, and acrocynosis

Question 9

Effects of Alpha-1 receptors stimulation

Answer 9

Vasoconstriction

vascular smooth muscle

Question 10

Epinephrine reversal is a phenomenon in which…

Answer 10

Epinephrine causes a reduction in BP while in the presence of a Alpha-Blocker

Question 11

Prazosin

Answer 11

Selective Alpha-blocker
*Alpha-1 blocker

Deceases BP and BPH

Question 12

Disadvantage of prazosin’s administration

Answer 12

Take every 8 hours

all others are once daily

Question 13

Phentolamine

Answer 13

Competitive alpha-1 and alpha 2 receptor blockers (balanced action on both: a1 = a2)
*Non-specfic and Short acting

Effect on BP is dose dependent:

• low doses = cardio-stim -> BP rises
• high doses = BP falls (alpha-1 mediated vasodilation)

Adverse effects limit its use for HTN (emergency only)
* used for pheochromocytoma

Question 14

Adverse affects of Alpha-Blockers

Answer 14

1. First dose orthostatic hypotension (head rush/dizzy spell) (most prominent with Prazosin)
2. Sinus-tachycardia (=> angina & palpitations) (more so w/ blockade of cardiac alpha-2-presynaptic receptors)
3. Syncope (passing out)
4. Vertigo

Question 15

Advise to give for the adverse affect of Prazosin?

Answer 15

• Reduce dose, Take w/ food

- Take first dose before bed

Question 16

Effect of Alpha-2 stimulation:

Answer 16

Inhibits release of NE from vesicles

decreases sympathetic stim