Digoxin: cardiac effects, elimination and monitoring
THE CONTEXT
Digoxin is a glycoside purified from the European foxglove, Digitalis lanata. Its effects differ between the atrioventricular node and other cardiac tissues.
Cardiac actions
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Digoxin slows conduction and prolongs the refractory period in the atrioventricular (AV) node, helping control the ventricular rate in atrial fibrillation (AF).
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In other cardiac tissues, including accessory pathways, it shortens refractory periods and enhances excitability and conduction.
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These effects outside the AV node may increase atrial and ventricular ectopic activity and lead to more complex atrial and ventricular tachyarrhythmias.
Elimination and dose adjustment
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Digoxin is largely excreted by the kidneys.
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The maintenance dose should be reduced in children, older people and patients with renal impairment.
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Digoxin is widely distributed and has a tissue half-life of 36 hours; its effects may persist for several days.
Monitoring
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Measurement of plasma digoxin concentration can help identify toxicity or undertreatment.