Case Study: Digoxin for AF

What are the main uses of digoxin?

Management of atrial fibrillation (AF) and symptom control in heart failure (HFrEF).

What is digoxin's mechanism of action in AF?

Slows ventricular response by suppressing AV node conduction.

What is digoxin's mechanism of action in heart failure?

Increases myocardial contractility (positive inotrope) and stimulates vagal tone.

Why is digoxin considered a high-risk medication?

It has a narrow therapeutic index, meaning small changes in dose can cause toxicity.

What is the therapeutic range for digoxin?

0.8–2.0 mcg/L (lower target 0.5–0.9 mcg/L for patients >65 years old).

When should digoxin levels be taken?

6 hours after the last dose.

What are common signs of digoxin toxicity?

Bradycardia, heart block, nausea, vomiting, abdominal pain, blurred/yellow vision, confusion, rash.

What are risk factors for digoxin toxicity?

Renal impairment, electrolyte disturbances (especially hypokalaemia), thyroid dysfunction.

What is the treatment for digoxin toxicity?

Stop digoxin, correct electrolytes, and administer Digoxin-specific antibody FAB fragments (DIGIFab) if severe.

What is the loading dose strategy for digoxin?

50% initially, followed by the rest 4-8 hours later, or slow loading over a week.

What is the typical maintenance dose of digoxin for AF?

125–250 mcg once daily.

What is the typical maintenance dose of digoxin for heart failure?

62.5–125 mcg once daily.

What is the bioavailability of digoxin from different preparations?

Tablet ~63%, Elixir ~75%, IV 100%.

Which mnemonic helps remember digoxin drug interactions?

'CRASED' - Calcium channel blockers, Rifampicin, Amiodarone, St John's Wort, Erythromycin, Diuretics.

Which type of drug interaction increases digoxin toxicity risk?

Drugs causing hypokalaemia, enzyme inhibitors increasing plasma levels, nephrotoxic drugs reducing excretion.

What clinical trials studied digoxin's effects in heart failure?

PROVED, RADIANCE, and DIG trials.

What clinical trial studied digoxin in atrial fibrillation?

AFFIRM trial.

Does digoxin reduce mortality in heart failure?

No, it mainly improves symptoms and reduces hospital admissions.

What is an important monitoring parameter after starting digoxin?

Electrolytes (K+, Mg2+, Ca2+), renal function (eGFR), thyroid function (TFTs).

What is the key counselling point for patients starting digoxin?

Report symptoms of toxicity promptly and adhere to blood test monitoring schedules.