Digoxin

Question 1

What class of drug is digoxin?

Answer 1

Cardiac glycoside

Question 2

What is the mechanism of action of digoxin?

Answer 2

Digoxin inhibits the Na+K+ ATPase pump
This results in an increase in intracellular sodium, which in turn results in an increase in intracellular calcium
This prolongs phase -0 and 4 of the cardiac action potential and increases force of contraction

Question 3

What is the overall effect of digoxin?

Answer 3

Positively inotropic - increase in force of contraction
Negtively chronotropic - decreased heart rate

Question 4

What are the clinical indications for digoxin?

Answer 4

Heart failure
Ventricualr rate control in supraventricular arrhythmias (particular AF and atrial flutter)

Question 5

What dose of digoxin is typically prescribed?

Answer 5

0.75-1.5mg in divided doses over 24 hours for rapid control of AF/flutter

125-250mcg daily for maintenance of AF/flutter

62.5-125mcg daily for heart failure

Question 6

What are the symptoms of digoxin toxicity?

Answer 6

Confusion
Loss of appetite
Nausea and vomiting
Diarrhoea
Arrhythmias
Yellow-green vision

Question 7

When should digoxin levels be taken if digoxin toxicity is suspected?

Answer 7

8 to 12 hours after the last dose of digoxin

Question 8

What factors can precipitate digoxin toxicity?

Answer 8

Hypokalaemia
Increasing age
Renal failure
Hypomagnesaemia
Hypothermia
Hypothyroidism
Hypernatraemia
Hypercalcaemia

Question 9

What drugs can increase the risk of digoxin toxicity?

Answer 9

Amiodarone
Quinidine
Verapamil
Spironolactone
Thiazide diuretics
Loop diuretics
Ciclosporin

Question 10

What is the management of digoxin toxicity?

Answer 10

Digibind - digoxin specific antibody
Correct arrhythmias
Monitor potassium

Question 11

What are the cautions for digoxin?

Answer 11

Sick sinus syndrome
Hypercalcaemia
Hypokalaemia
Hypomagnesaemia
Recent MI
Thyroid disease

Question 12

What does digoxin interact with?

Answer 12

Amiodarone - causes increased digoxin plasma concentration
Calcium channel blockers - cause increased plasma concentration of digoxin
Drugs which cause hypokalaemia - diuretics, PPIs

Question 13

What information should be given to patients about digoxin?

Answer 13

Patients should be made aware of the symptoms of digoxin toxicity
- nausea, vomiting, visual disturbance, confusion or dizziness