24th April 2024

Digoxin

Digoxin is a cardiac glycoside that increases the force of myocardial contraction and reduces conductivity within the atrioventricular node. Contractility is enhanced via inhibition of the myocardial Na-K ATPase pump, which leads to increased intracellular sodium and calcium in the heart.  Stimulation of the parasympathetic nervous system inhibits the AV node, reducing the heart rate. Digoxin is used for rate control in atrial fibrillation or flutter and symptomatic relief (rather than mortality benefit) in heart failure. 

Digoxin monitoring is not routinely indicated unless toxicity is suspected where levels should be taken 8-12 hours post-dose. Note that toxicity can occur with serum digoxin concentrations within the therapeutic range. Features suggestive of digoxin toxicity include confusion, nausea, anorexia, disturbance of colour vision, and cardiac conduction disturbances. Several factors can precipitate toxicity, including hypokalaemia, renal impairment, hypoalbuminemia and concurrent prescribing of medications (amiodarone, antimicrobials, calcium channel blockers, chloroquine, spironolactone).