⚠️ Electrolyte imbalance: Hypokalaemia, hypomagnesaemia, and hypercalcaemia all increase the risk of digoxin-induced arrhythmias (via Na⁺/K⁺ ATPase inhibition). Monitor renal function, electrolytes, and serum digoxin levels regularly.

📖 About

Cardiac glycoside derived from Digitalis species.
Commonest UK preparation: Digoxin (not digitoxin or ouabain).
Main indication in UK: rate control in atrial fibrillation (particularly sedentary patients, elderly, or with concomitant heart failure).
Also used in heart failure with reduced EF for symptomatic relief if symptoms persist despite optimal therapy (ACEi/ARB/ARNI, β-blocker, MRA).

⚙️ Mode of Action

Inhibits membrane-bound Na⁺/K⁺-ATPase pump.
↑ Intracellular sodium → reduced sodium–calcium exchange → ↑ intracellular calcium → positive inotropy.
Vagomimetic effect: slows AV nodal conduction → ventricular rate control at rest in AF/flutter.
Less effective for rate control during exertion.
Excess → ↑ automaticity, after-depolarisations, and arrhythmias.

🩺 Indications & Typical Dosing

AF with rapid ventricular response: IV loading may be used for acute rate control.
Chronic AF (sedentary patients): Oral maintenance dosing.
Heart failure with reduced EF: Symptom relief, not mortality benefit.

💊 Dosing – Digoxin (BNF; verify locally)

Regimen	Details
⚡ IV Loading (acute AF)	• 750 mcg–1 mg IV over ≥2 h • Reduce dose if elderly or in renal impairment
📖 Oral Loading (stable AF)	• 500 mcg PO → repeat 500 mcg PO after 6–12 h • Use 250 mcg for second dose if elderly/frail
🩺 Maintenance	• 62.5–250 mcg PO OD • Lower doses in elderly or renal impairment
🔄 IV → PO Conversion	• 125 mcg PO ≈ 80 mcg IV

🔄 Interactions

↑ Digoxin levels: Amiodarone, verapamil, quinidine, macrolides (clarithromycin, erythromycin).
Electrolyte disturbances: Hypokalaemia (diuretics, steroids), hypomagnesaemia, hypercalcaemia increase toxicity risk.
Renal impairment: ↓ clearance → ↑ toxicity risk.

🚫 Contraindications

Wolff–Parkinson–White (WPW) syndrome with AF (may accelerate conduction via accessory pathway → VF).
Second-/third-degree AV block or severe bradycardia.
Hypertrophic cardiomyopathy with outflow obstruction.
Caution: renal failure, elderly, electrolyte disturbances.

❗ Side Effects

GI: Nausea, vomiting, diarrhoea, abdominal pain.
CNS: Confusion, fatigue, delirium, psychosis.
Visual: Blurred vision, yellow-green tinge (“xanthopsia”).
Arrhythmias: Almost any - classically atrial tachycardia with block, multifocal atrial tachycardia, ventricular ectopics, VT/VF, high-degree AV block, asystole.
Characteristic ECG: “reverse tick” ST depression, T-wave changes (not always toxic).

🚨 Digoxin Toxicity

Check serum digoxin levels: aim 0.5–1.0 mcg/L (toxic if >2 mcg/L, though toxicity may occur at lower levels).
Correct hypokalaemia, hypomagnesaemia; maintain K⁺ >4 mmol/L.
Digoxin-specific antibody fragments (Digibind) for life-threatening toxicity (severe arrhythmia, hyperkalaemia, haemodynamic instability).
Avoid DC cardioversion unless absolutely necessary (can trigger VF).
Pacing may be needed for bradyarrhythmia/AV block.

📚 References

BNF: Digoxin
NICE CG180: Atrial fibrillation (management)

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Digoxin 💊