Digoxin

Question 1

When is digoxin indicated for use?

Answer 1

• AF
• Atrial flutter
• Severe heart failure

Question 2

How is digoxin used in AF/atrial flutter?

Answer 2

To reduce ventricular rate via indirect pathway involving increased vagal tone, which reduces AV node conduction, preventing impulses being transmitted to ventricles

Question 3

How is digoxin used in Severe heart failure?

Answer 3

Third-line treatment in patients who are already taking ACEi, B-blocker and either ARBs or aldosterone antagonists

Question 4

How does digoxin generally work?

Answer 4

Negative chronotropic (reduces heart rate) and positiviely intotropic (increases force of contraction)

Question 5

What is the mechanism of digoxin in heart failure?

Answer 5

Direct effect on myocytes through inhibition of Na+/K+-ATPase pumps, causing Na+ to accumulate in the cell. As cellular extrusion of Ca2+ requires low intracellular Na+ concentrations, elevation of intracellular Na+ causes Ca2+ to accumulate in the cell, increasing contractile force

Question 6

What are the main adverse effects of digoxin?

Answer 6

• Bradycardia
• GI disturbance
• Rash
• Dizziness
• Visual disturbance
• Arrythmias

Question 7

What visual disturbances can occur with digoxin use?

Answer 7

Blurred or yellow vision

Question 8

When is digoxin contra-indicated for use?

Answer 8

• Second-degree heart block
• Intermittent compltete heart block
• Risk of ventricular arrythmias

Question 9

What electrolyte abnormalities can increase the risk of digoxin toxicity?

Answer 9

• Hypokalaemia
• Hypomagnasaemia
• Hypercalcaemia

Question 10

Why can hypokalaemia cause digoxin toxicity?

Answer 10

Digoxin competes with potassium to bind the Na+/K+-ATPase pump. When serum potassium levels are low, competition is reduced and the effects of digoxin are enhanced

Question 11

What are important interactions to be aware of when using digoxin?

Answer 11

• Loop/thiazide diuretics - can cause hypokalaemia
• Amiodarone
• CCBs
• Spironolactone
• Quinine

Question 12

How can digosxin be administered?

Answer 12

• Oral
• IV

Question 13

How long after IV administration of digoxin would you see an effect?

Answer 13

30 mintues

Question 14

How long after administration of oral digoxin would you see an effect?

Answer 14

2 hours

Question 15

Why is a loading dose required for digoxin if rapid effect is needed?

Answer 15

Due to its large volume of distribution

Question 16

What dose of digoxin would you give as a loading dose if you wanted to obtain rapid effect of the drug?

Answer 16

500 micrograms, followed by 500 micrograms 4 hours later. Maintenance of 62.5-250 micrograms daily following this

Question 17

What does the maintenance dose of digoxin depend on?

Answer 17

• Heart rate
• Renal function

Question 18

How would you note a loading dose of digoxin in a drug kardex?

Answer 18

In the once only section. Maintenance is written in regular meds section

Question 19

What parameters would you use to monitor digoxin therapy?

Answer 19

• Symptoms
• Heart rate
• Renal function
• ECG
• Electrolytes

Question 20

What ECG changes can the therapeutic dose of digoxin cause?

Answer 20

ST-segment depression - reverse tick sign

Question 21

What might the “reverse tick sign” on ECG indicate in someone taking digoxin?

Answer 21

Expected effect - does not signify toxicity

Question 22

Why can digoxins effect on AF be lost during stress and exercise?

Answer 22

It relies on increasing parasympathetic tone - in these states sympathetic is to overpowering. This is why it is a better option for sedentary patients

Question 23

Can digoxin toxicity occur when digoxin levels are within therapeutic range?

Answer 23

Yes