Antiarrhythmic Drugs: Points of Note

Key points

• Digoxin: narrow therapeutic index; toxicity → arrhythmias, GI upset, yellow vision (xanthopsia); levels ≥6 h post-dose; toxicity worsened by hypokalaemia.
• Amiodarone: half-life 20–100 days; side effects — thyroid dysfunction, corneal deposits, pulmonary fibrosis, photosensitivity, hepatitis; P450 inhibitor (↑ warfarin).
• Sotalol: class III + beta-blocker; proarrhythmic (torsades); avoid in asthma.
• Flecainide: contraindicated post-MI and in structural heart disease.
• Verapamil: negatively inotropic — avoid in heart failure and with beta-blockers.