Key investigations

Key investigations for chronic digoxin accumulation are:

  • electrocardiogram (ECG)—see Clinical presentation for ECG changes
  • serum digoxin concentration1 —measure an initial serum digoxin concentration at least 6 hours after the patient’s last digoxin dose, then every 12 to 24 hours until the concentration is within the therapeutic range, unless digoxin-specific immune antibody fragments (digoxin immune Fab) have been given
  • serum electrolyte concentrations (potassium, sodium, bicarbonate, magnesium, calcium)
  • serum urea and creatinine concentrations.

Serum digoxin concentrations cannot be interpreted after digoxin immune Fab has been given. Most assays measure total digoxin concentration in the serum—this increases after giving digoxin immune Fab, because the antibodies bind digoxin in the circulation. Free serum digoxin concentration can be measured, but the assay is not as readily available, and the result is unlikely to change management. Further management is guided by symptoms.

1 Australian laboratories report serum digoxin concentrations as microgram/L or nanomol/L. To convert microgram/L to nanomol/L, multiply by 1.28.Return