Beta Antagonists/Blockers

Question 1

Why are beta blockers used in tachycardia?

Answer 1

increases automaticity - beta blockers decreases sympathetic drive

Question 2

Why are beta blockers used in atrial fibrillation and supraventricular tachycardia?

Answer 2

delay AV nodal conduction

Question 3

Give an example of a partial agonist?

Answer 3

alprenolol

Question 4

Why are beta blockers used in arrhythmias?

Answer 4

excess sympathetic drive - stress, emotion or disease - tachycardia - increased automaticity - beta blockers decrease sympathetic drive

Question 5

When are beta blockers used in hypertension?

Answer 5

when angina is present as they can treat both

Question 6

How do beta blockers cause fatigue?

Answer 6

reduce CO (beta 1) and prevent vasodilation of arterial smooth muscle ( beta 2)- less blood supply

Question 7

What does the effect of beta blockers dependent on?

Answer 7

level of sympathetic activity as they require an agonist to work

Question 8

Why are beta blockers used in compensated heart failure?

Answer 8

increased sympathetic drive - predisposes to arrhythmias - low dose beta blocker - reduces sympathetic drive - improves mortality and morbidity

Question 9

Why should beta blockers be avoided in asthmatics?

Answer 9

cause bronchospasm - block airway smooth muscle beta 2 adrenoceptors

Question 10

What type of beta blocker is propranolol?

Answer 10

non-selective

Question 11

How do non-selective beta blockers work?

Answer 11

exercise or stress - rate, force and CO reduced - reduce oxygen demand - better oxygenation of myocardium - also decreases maximal exercise tolerance, slight coronary artery vasoconstriction via beta 2 adrenoceptors blockage

Question 12

What is the meaning of a non-selective beta blocker?

Answer 12

equal affinity for beta 1 and beta 2

Question 13

What is the mechanism of action of beta blockers?

Answer 13

exercise or stress - rate, force and CO reduced - reduced oxygen demand - better oxygenation of the myocardium - decreases maximal exercise tolerance

Question 14

Why should beta blockers be avoided in diabetics?

Answer 14

can cause hypoglycaemia - release of glucose from the liver controlled by beta 2 adrenoceptors - reduced glucose output, increased HR and force warn of hypo - warning mechanism removed

Question 15

How do beta blockers aggravate cardiac failure?

Answer 15

patients at rely on sympathetic drive to maintain CO

Question 16

Why is carvedilol used in compensated heart failure?

Answer 16

additional alpha 1 antagonist activity - vasodilation - reduces total peripheral resistance - reduces work of the heart - start low, increase slow

Question 17

What are the adverse effects of beta blockers?

Answer 17

bronchospasm, aggravation of cardiac failure, bradycardia, hypoglycaemia, fatigue, cold extremities

Question 18

What are partial agonists?

Answer 18

non-selective, mild stimulatory effect in the absence of other agonists, block effect of strong agonists

Question 19

Why are beta blockers used in angina?

Answer 19

first line - alternative to calcium channel blockers - reduces oxygen consumption - reduces pain

Question 20

What is the meaning of a selective beta blocker?

Answer 20

blocks beta 1 adrenoceptors only

Question 21

Give examples of selective beta blockers ?

Answer 21

atenolol, bisoprolol and metoprolol

Question 22

How do beta blockers cause cold extremities?

Answer 22

loss of beta 2 adrenoceptor mediated vasodilation