Cardiac Glycoside

The answer first

Cardiac glycosides — principally digoxin (the dominant agent in clinical practice) and digitoxin (still used in parts of Europe) — are among the oldest cardiovascular drugs and have moved from a near-universal therapy for heart failure and atrial fibrillation to a niche role, but recent evidence from the RATE-AF, ARISTOCRAT, and the recent low-dose digoxin randomized controlled trial has driven a disciplined reconsideration of their use. Digoxin retains a defined role for rate control in atrial fibrillation (particularly in heart failure with reduced ejection fraction where negative-inotropic agents are problematic) and for symptom relief in heart failure with reduced ejection fraction already on optimal therapy. It has a narrow therapeutic index, requires dose individualisation by renal function and patient factors, must be monitored by serum concentration (target 0.5 to 0.9 ng/mL in heart failure, up to 2 ng/mL for rate control), and its toxicity — cardiac arrhythmia, hyperkalaemia, nausea, visual disturbance, confusion — is treated with digoxin-specific antibody fragment. ^{[2] [11]}

The FRACP candidate must be able to defend three positions without hedging: (1) digoxin is now reserved for heart failure with reduced ejection fraction already on optimal quadruple therapy with persistent symptoms, and for rate control in atrial fibrillation when standard agents fail or are contraindicated; (2) the contemporary target serum digoxin concentration for heart failure is 0.5 to 0.9 ng/mL (not the historical 0.8 to 2 ng/mL), and higher concentrations are associated with increased mortality without additional benefit; and (3) digoxin toxicity presents with non-specific features (nausea, anorexia, confusion, visual disturbance with yellow-green halos) and cardiac arrhythmia (premature ventricular contractions, atrial tachycardia with block, bradycardia, ventricular fibrillation), and is treated with digoxin-specific Fab antibody fragments — particularly with life-threatening arrhythmia, hyperkalaemia above 5 mmol/L, a digoxin concentration above 6 ng/mL in acute overdose or above 4 ng/mL in chronic toxicity, or end-organ dysfunction. Lead with the decision, then the evidence, then the trap. ^{[2] [11]}

References12ShowHide

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