Digoxin (High risk)

Question 1

List the common indications for Digoxin

Answer 1

1) Atrial fibrillation (AF) and atrial flutter, digoxin is used to reduce the ventricular rate. (However, a β-blocker or non-dihydropyridine CCB is usually more effective)
2) Severe heart failure, digoxin is an option in patients who are already taking an ACE inhibitor, β-blocker and either an aldosterone antagonist or angiotensin receptor blocker.

Question 2

what is the dose of digoxin for the following indications:

1) Maintenance, for AF or flutter
2) Heart failure (for patients in sinus rhythm)

Answer 2

1) Maintenance, for AF or flutter: 125–250 mcg daily, dose according to renal function and initial loading dose, reduce dose in the elderly.
2) Heart failure: 62.5–125 mcg od, reduce in the elderly.

Question 3

Outline the MoA of digoxin

Answer 3

Digoxin is a cardiac glycoside that increases the force of myocardial contraction and reduces conductivity within the atrioventricular (AV) node

Question 4

List the Important adverse effects caused by digoxin (6)

Answer 4

1) Arrhythmias
2) Bradycardia
3) GI disturbance (diarrhoea, nausea, vomiting)
4) Rash (skin reactions)
5) Dizziness
6) Visual disturbance (blurred or yellow vision)

Question 5

How should the dose of digoxin be adjusted when used concurrently with amiodarone, dronedarone and quinine?

Answer 5

Manufacturer advises reduce dose by HALF

Question 6

If digoxin or another cardiac glycoside has been given previously, how should the dose be adjusted?

Answer 6

Dose may need to be reduced if digoxin (or another cardiac glycoside) has been given in the preceding 2 weeks.

Question 7

When switching from intravenous to oral digoxin, how much should the dose be increased to maintain the same plasma-digoxin concentration?

Answer 7

Increase dose by 20–33%

Question 8

who should digoxin be used in caution with?

Answer 8

1) Hypercalcaemia, Hypokalaemia, hypomagnesaemia, hypoxia (all increase risk of digitalis toxicity)
2) Recent myocardial infarction
3) Severe respiratory disease
4) Sick sinus syndrome
5) Thyroid disease

Question 9

Digoxin may worsen conduction abnormalities, so is contraindicated in which patients?

Answer 9

1) Second-degree heart block and intermittent complete heart block.
2) It should not be used in patients with or at risk of ventricular arrhythmias

Question 10

Certain electrolyte abnormalities increase the risk of digoxin toxicity, including hypokalaemia, hypomagnesaemia and hypercalcaemia. Potassium disturbance is the most important of these, explain why.

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

In what patients should the dose of digoxin be reduced? (2)

Answer 11

1) Reduce in renal failure, as digoxin is eliminated by the kidneys
2) Elderly

Question 12

How long after a dose should blood be taken in order to conduct a plasma-digoxin concentration assay?

Answer 12

At least 6 hours after a dose

Question 13

what parameters should be monitored in patients taking digoxin?

Answer 13

Monitor serum electrolytes and renal function (Toxicity increased by electrolyte disturbances)

Question 14

Outline the important interactions to be aware of with regards to digoxin

Answer 14

1) Loop and thiazide diuretics can increase the risk of digoxin toxicity by causing hypokalaemia
2) Amiodarone, CCBs, spironolactone and quinine can all increase the plasma concentration of digoxin and therefore the risk of toxicity

Question 15

outline the symptoms of digoxin overdose?

Answer 15

1) A wide range of arrhythmias can occur

2) Confusion, loss of appetite, nausea, vomiting, diarrhoea, or vision problems

Question 16

when is a loading dose of digoxin given and how should this be initiated?

Answer 16

1) By either route, a loading dose is required if a rapid effect is needed.
2) 500 mcg , followed by 250–500 micrograms 6 hours later, depending on response. Thereafter, the usual maintenance dose is 125–250 micrograms daily.