Digoxin

Synonyms / Brand Names:

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Dosing and Administration

Because the pharmacokinetics of Digoxin are complex, and because toxic levels of Digoxin are only slightly higher than therapeutic levels, Digoxin dosing can be difficult. The recommended approach is to:

estimate the patient’s daily maintenance dose;
adjust the estimate to account for patient-specific factors;
choose a dosing regimen;
monitor the patient for toxicity and for therapeutic effect, if possible; and
adjust the dose.

Estimated daily maintenance dose

Children > 2 years old - daily oral dose 10 mcg/kg/day
Prepubertal children - daily oral dose 10 mcg/kg/day
Adults - daily oral dose 3 mcg/kg/day

These doses will, in uncomplicated patients, tend to produce steady-state post-absorptive levels of 1 to 2 ng/mL, but the confidence limits around this range are wide.

ECG changes

ECG changes typical for digoxin use (digoxin = Lanoxin) are:

Oddly shaped ST-depression with 'scooped out' appearance of the ST segment (see figure)
Flat, negative or biphasic T wave
Short QT interval
Increased u-wave amplitude
Prolonged PR-interval
Sinus bradycardia

ECG changes typical for digoxin intoxication are:

Bradyarrhythmias:

- AV block. Including complete AV block and Wenkebach.

Tachyarrhythmias:

- Junctional tachycardia
- Atrial tachycardia
- Ventricular ectopia, bigemini, monomorphic ventricular tachycardia, bidirectional ventricular tachycardia

Intoxication can lead to an SA-block or AV-block, sometimes in combination with tachycardia. NB these effects are increased by hypokalemia. In extreme high concentrations rhythm disturbances (ventricular tachycardia, ventricular fibrillation, atrial fibrillation) may develop.

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