B - 7. a-receptor antagonists

Question 1

Alpha receptors

Answer 1

a1 - walls of blood vessels, pupils, urinary sphincter etc

a2 - on presynaptic neuron - negative feedback

Question 2

a1 blockers SE

Answer 2

Hypotension
Headaches
Nasal congestion
Ejaculation problems

Question 3

a2 blockers SE

Answer 3

Uncontrolled catecholamine release

B-receptor stimulus increase -> HR up

Question 4

Selective a1 blockers names

Answer 4

Prazosin
Doxazosin
Tamsulozin (less effective, works on a-1A)
Urapidil (also 5-HT receptor agonist)
carvedilol (a1 blocker and uselective B blocker)

Question 5

Selective a1 blockers main action

Answer 5

Vasodialation

Question 6

Non-selective alpha blockers names

Answer 6

Phentolamine (blocks both a1 and a2)

- reversible, competative

Question 7

Non-selective alpha blockers indications

Answer 7

Hypertensive crisis in pheochromocytoma

Cocaine induced cardiovascular emergencies (you want to avoid beta blockers)

Question 8

Reflex tachycardia

Answer 8

a1 receptor blocked -> vasodialation -> hypotension -> sensed by baroreceptor reflex -> increased sympathetic firing to heart (B1 receptors) -> increased heart rate

-this will be much more prominent with non selective blockers as a2 block hinders negative feedback of catecholamines