Alpha Adrenoreceptor Antagonists

Question 1

1) What do alpha1 adrenoreceptors blockers do?

2) What are the effects of this?

Answer 1

1) Lower BP by blockade of post synaptic alpha1 adrenoreceptors.
2) dilation of arteriolar resistance vessels, lowering peripheral resistance and dilation of venous capacitance vessels, reducing venous return and CO.

Question 2

1) What do non-selective alpha blockers cause that selective alpha1 blockers do not cause?
2) In what situation are non selective alpha blockers used?

Answer 2

1) Reflex tachycardia.

2) peri operative management of pheochromocytoma.

Question 3

1) What is the beneficial effect on plasma lipids that can be cause by alpha blockers?
2) What other condition can selective alpha1 blockers be used to treat?

Answer 3

1) They can increase HDL cholesterol and reduce triglycerides.
2) Bladder outflow obstruction.

Question 4

1) Which alpha blockers undergo extensive first pass hepatic metabolism?

Answer 4

1) selective alpha1 blockers.

Question 5

1) When are alpha adrenoreceptors antagonists used in a CVS situation?
2) Name the 2 P-drugs that are highly selective for the alpha1 adrenoreceptor.
3) Where are alpha1 adrenoreceptors commonly found?

Answer 5

1) As an add on treatment in resistant hypertension when other drugs are insufficient.
2) Doxazosin and Tamulosin.
3) In smooth muscle in blood vessels and urinary tract (bladder neck and prostate).

Question 6

1) What does stimulation of alpha1 receptors do?
2) What does blockade of alpha1 receptors do?
3) Therefore, what is the overall effect of alpha1 blockers?
4) Which conditions are alpha blockers contraindicated in?

Answer 6

1+2) Stimulation induces contraction, blockade induces relaxation.

3) Vasodilation and reduced BP, and reduced resistance to bladder outflow.
4) patients with existing postural hypotension.

Question 7

1) Aside from resistant hypertension, what other conditions can alpha blockers be used in?
2) What is the specific class of these alpha blockers and give an example.

Answer 7

1) Used as a first line treatment in BPH when lifestyle changes are insufficient.
2) 5 alpha reductase inhibitors; Tamulosin.

Question 8

List 3 important side effects of alpha blockers.

Answer 8

Dizziness, postural hypotension and syncope as a result of their effect on vascular tone. Effects are particularly prominent after first dose.

Question 9

1) Why does reflex tachycardia happen with use of no selective alpha blockers?
2) Why should doses of beta blocker in particular be omitted on the day of starting an alpha blocker?

Answer 9

1) A compensatory mechanism for the vasodilation.

2) Because beta blockers inhibit the reflex tachycardia.

Question 10

1) What is the cause of postural hypotension when using alpha blockers?

Answer 10

1) Venous pooling.

Question 11

1) What is Doxazosin licensed for?

2) What is Tamulosin licensed for?

Answer 11

1) Hypertension AND BPH.

2) BPH only.