Cardiac (specialist) medication

Question 1

What are two main conditions that digoxin is particularly helpful for? Why? - explain its effects

Answer 1

• Heart failure with reduced ventricular function: increases contractility of heart
• Atrial fibrillation: rate control - slows down AVN conduction

Question 2

How is digoxin derived?

Answer 2

Digitalis plant (foxglove)

Question 3

Contraindications of digoxin. - consider both cases of bradycardia and tachycardia.

Answer 3

• Bradycardia (<60BPM): i,e, with complete heart blocks, 2nd degree block
• Ventricular tachycardia/fibirllation
• SVT associated with accessory conducting pathways i.e. Wolff-Parkinson-White Syndrome (can trigger it even more)

Question 4

Cautions in prescribing digoxin: what factors might increase risk of digoxin toxicity?

Answer 4

• Renal disease - reduced clearance
• Hypokalaemia and hypomagnesemia
• Hypercalcaemia
• Recent MI

Question 5

Digoxin - mechanism of action.

Answer 5

1. Blocks N+/K+ ATPase, causing increased intracellular Na+
2. Causes increased activation of Na/ca2+ exchanger (Na+ out and Ca2+ in)
3. Resulting in higher Ca2+ leading to increased contractility.

This is why hypercalcaemia is a RF of toxicity.

Question 6

Describe a patient presentation suggestive of digoxin toxicity e.g. in overdose or people with RFs. Say they have just started digoxin.

List 3 systems

Answer 6

• N/V, anorexia
• Neuro: Vision changes, fatigue, confusion
• Arrythmias, bradycardia, hyperkalaemia and electrolyte abnormalities
• Death

Question 7

What is the toxic level of digoxin? When is it usually measured?

Answer 7

2.0

Taken at least 6 hours after a dose

Question 8

Management of digoxin toxicity.

Answer 8

1. Withdrawal of drug
2. If severe, use digibind