Beta Blockers (Atenolol)

Question 1

In what conditions is a beta blocker (e.g. Atenolol) used as a first line treatment for?

Answer 1

1) Ischemic heart disease - to improve symptoms of angina and acute coronary sydrome.
2) Chronic heart failure - improves prognosis.
3) Atrial fibrillation - to reduce ventricular rate. Also maintains sinus rhythm in paroxysmal atrial fibrillation.
4) Supraventricular tachycardia (used to restore sinus rhythm)

Question 2

When would a beta blocker be used to treat hypertension?

Answer 2

Beta blockers are used as a 2nd line intervention for hypertension. Either when ACEi or Ca2+ channel blockers are inappropriate or insufficient.

Question 3

How do beta blockers work to :
1) relieve myocardial ischaemia
2) slow ventricular rate in Atrial Fibrillation
3) lower blood pressure
????

Answer 3

Beta1 adrenoreceptors are in the heart. When these receptors are blocked :

1) - reduces force of contraction
- speed of conduction ==> reduces heart rate.
- so the heart is working less —> so needs less oxygen —>more time for oxygen perfusion —-> less ischemia.

2) Prolongs refractory period of the AV node —> slows ventricular heart rate.
3) Reduces renin secretion via kidneys —> lowers BP

Question 4

What are the side effects of beta blockers?

Answer 4

1) fatigue
- cold peripheries
- headache
- GI disturbance (nausea)
- sleep disturbance and nightmares
6) impotence

Question 5

Why should beta blockers such as propanol not be used in asthma?

Answer 5

B1 receptors are in the heart. B2 receptors are on the surface of smooth muscle. When beta blockers bind to the b2 receptors on the smooth muscle of the airways it causes life threatening bronchospasm.

Question 6

Which beta blocker can be used in COPD?

Answer 6

A B1 selective beta blocker such as atenolol an be used in COPD

Question 7

Why are beta blockers contraindicated in heart block?

Answer 7

In heart block the electrical activity from the atrium is not conducted to the ventricles normally. Leading to decreased rate of contraction of the ventricles.

Beta blockers work by slowing the conduction of depolarisation waves through the AV node.

If used in heart block heart rate would become dangerously slow.

Question 8

How should we modify the dose of beta blockers in :

1) heart failure
2) hepatic failure

Answer 8

1) in heart failure start with a low dose and increase it slowly as initially beta blockers can impair cardiac function.
2) in hepatic failure give a reduced dose.

Question 9

In what conditions should we avoid beta blockers?

Answer 9

1) asthma
2) heart block
3) haemodynamic instability

Question 10

What drug do beta blockers interact with?

Answer 10

Beta blockers interact with Non-dihydropyridine calcium channel blockers such as verapamil and diltiazem.

The combination can cause heart failure, bradycardia and asystole.

Question 11

What are the side effects of the interaction between beta blockers and non-dihydropyridine calcium channel blockers?

Answer 11

Heart failure
Bradycardia
Asystole