Pharmacokinetics/pharmacodynamics

Digoxin is a cardiac glycoside. Digoxin’s mechanism of action is related to both causing an increase in parasympathetic tone as well as inhibition of the Na⁺/K⁺ ATPase, which indirectly increases intracellular calcium. Its onset of action is 5 to 60 minutes when given intravenously, with peak effect seen in 1 to 6 hours. When given orally, onset of action is 1 to 2 hours, with peak effect seen at 2 to 8 hours. The half-life of digoxin varies by age, ranging from 61 to 170 hours in preterm neonates, from 35 to 45 hours in full-term neonates and from 18 to 25 hours in infants.[27] Digoxin toxicity in neonates and infants can present as significant bradycardia or cardiac arrhythmias. Digoxin is contraindicated in patients with WPW because of its effect on the accessory pathway and the AV node causing predisposition for fatal arrhythmias.[28]