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Antiarrhythmic Pregnancy: C — can be used if clinically necessary; neonatal levels approximate maternal

Digoxin

Brand names: Lanoxin

Adult dose

Dose: Loading: 0.5–1mg in divided doses over 24h. Maintenance: 62.5–250mcg OD
Route: Oral / IV
Frequency: Once daily (maintenance)
Max: 1.5mg loading; 250mcg/day maintenance
IV loading for rapid AF rate control: 0.75–1mg IV in 50ml glucose 5% over 2h. Oral loading: 250–750mcg, then 250mcg every 6–8h to total ~1.5mg. Maintenance guided by levels (0.5–0.9 ng/ml target in HF).

Dose adjustments

Renal

Renally excreted — reduce dose significantly in CKD. GFR 10–50: 62.5–125mcg OD. GFR <10: 62.5mcg every 48h. Monitor levels.

Hepatic

No adjustment required.

Clinical pearls

  • Digoxin has a NARROW therapeutic index: toxicity at levels >2.0 ng/ml. Levels 0.5–0.9 ng/ml are optimal for HF (higher levels do not improve outcomes and increase toxicity — DIG trial).
  • Toxicity antidote: digoxin-specific antibody fragments (DigiFab). 1 vial neutralises ~500mcg. Use for life-threatening arrhythmia/toxicity.
  • Hypokalaemia is the commonest cause of digoxin toxicity. Maintain K+ >3.5 mmol/L. Hypomagnesaemia sensitises myocardium similarly.
  • Digoxin does NOT improve mortality in HFrEF (DIG trial) — it reduces hospitalisation. Use for symptom control, not prognostic benefit.
  • In AF: digoxin provides rate control at rest but poor exercise rate control. Use bisoprolol as first-line.

Contraindications

  • Wolff-Parkinson-White syndrome (can accelerate antegrade conduction via accessory pathway)
  • Ventricular fibrillation or ventricular tachycardia
  • Hypertrophic obstructive cardiomyopathy (except if concomitant AF)
  • Hypokalaemia, hypomagnesaemia (increases toxicity risk — correct first)

Side effects

  • Toxicity: nausea, vomiting, visual disturbance (yellow-green halos), confusion
  • Bradycardia, AV block (first sign of toxicity)
  • Arrhythmias (any type — especially with hypokalaemia)
  • Gynaecomastia (rare)
  • Anorexia

Interactions

  • Amiodarone: doubles digoxin levels — reduce digoxin dose by 50%
  • Furosemide: hypokalaemia from furosemide potentiates digoxin toxicity
  • Clarithromycin / erythromycin: increased digoxin absorption and levels
  • Calcium: IV calcium in hyperkalaemia — use with extreme caution (risk of cardiac arrest)
  • Verapamil: significantly increases digoxin levels and additive bradycardia

Monitoring

  • Digoxin levels (trough
  • >6h post-dose; target 0.5–0.9 ng/ml)
  • U&E (K+
  • Mg²⁺)
  • creatinine
  • ECG (PR interval
  • QT
  • ST changes)

Reference: NICE NG106 Chronic HF; DIG Trial NEJM 1997; NICE BNF 84. Verify against your local formulary and the latest BNF before prescribing.

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Curated clinical cross-links plus same-class fallbacks.

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