Bioavailability of oral dose 60 to 85%.
Half-life in infants 18 to 25 hours. 50 to 70% excreted in urine unchanged. Minimally metabolised by hepatic and intestinal enzymes to active and inactive metabolites.
Onset of effect occurs 0.5–2 hours after initial oral dose of 500–750 micrograms and 5–30 minutes after initial IV dose of 400–600 micrograms; maximal effect occurs after 1–4 hours (IV) or 2–6 hours (oral).
Regularly assess patients for digoxin toxicity (including resting heart rate); routine measurement of pulse rate before giving next dose of digoxin is not necessary
Assume that any arrhythmia that occurs in a child taking digoxin is due to the drug until proven otherwise.
DigiFab (digoxin immune Fab) is available for the treatment of life-threatening overdoses of digoxin:
Dose initially with one vial (40 mg diluted in 4 mL of water for injections) and repeat if symptoms persist or recur.
Full neutralisation dose of DigiFab is: Number of vials = serum digoxin concentration (nanogram/mL) x weight (kg) / 100 (rounded up to nearest vial). However, this is rarely indicated.
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