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Lab Test: Digoxin Level

    Lab Test
    •  Digoxin Measurement
    Description
    • Measurement of digoxin in serum for the evaluation and management of patients receiving digoxin or who have ingested digoxin-like compounds (e.g., cardiac glycosides).
    Reference Range
    • Therapeutic concentration:  0.8-2 ng/mL (1-2.6 nmol/L)
    • Toxicity:
      • Adults: > 2.5 ng/mL (> 3.2 nmol/L)
      • Children: > 3 ng/mL (> 3.8 nmol/L)
    Indications & Uses
    • Digitalized patients with hypomagnesemia
    • Suspected and known atrial fibrillation in patients receiving digoxin
    • Drug level monitoring during digoxin therapy
    • Suspected and known atrial tachycardia
    Clinical Application
    • While the official upper limit of the therapeutic range is 2 ng/mL, there is some evidence to suggest that mortality in heart failure is improved at levels of 0.5 ng/mL to 0.8 ng/mL, although others suggest that 1 ng/mL to 2 ng/mL is an appropriate therapeutic range.  The specimen should be obtained 12 hours after a dose of digoxin or just before the next dose is due to be given
    • Magnesium deficiency increases the risk of digitalis toxicity and arrhythmias, which may be caused by intracellular potassium depletion.
    • Digoxin toxicity is often associated with paroxysmal atrial tachycardia with a variable degree of block and/or atrial fibrillation with complete heart block and a slow, regular, wide QRS complex ventricular escape rhythm.
    • Results increased in:
      • Hypothyroidism
      • Medications that inhibit P-gp (e.g., amiodarone, diltiazem, verapamil)
      • Older patients
      • Renal failure

     The Evidence & Mechanism: Amiodarone - Digoxin Drug Interaction

    • Amiodarone use in a patient on stable doses of digoxin can result in significant digoxin toxicity.
    • This is clinically significant and should not be missed.
    • EBM Consult Article:  Click Here
    • Results decreased in:
      • Hyperparathyroidism
      • Pregnancy
      • Physical activity prior to testing
    Related Tests
    • Serum creatinine level
    • Serum Magnesium level
    • Serum Potassium level
    Drug-Lab Interactions
    • Canrenoate - false increases or decreases in digoxin levels
    • Capromab Pendetide - falsely high digoxin serum levels
    • Chan Su - false increases in digoxin concentrations
    • Cortisone - false increases in digoxin levels
    • Dexamethasone - false increases in digoxin levels
    • Digitoxin - false increases in digoxin levels
    • Digoxin Immune Fab (Ovine) - false increases in digoxin levels
    • Fludrocortisone - false increases in digoxin levels
    • Fluorescein - invalid digoxin assay results
    • Ginseng, American - false readings in digoxin concentrations
    • Ginseng, Chinese - false readings in digoxin concentrations
    • Ginseng, Siberian - false readings in digoxin concentrations
    • Hydrocortisone - false increases in digoxin levels
    • Kyushin - false increases in digoxin concentrations
    • Methylprednisolone - false increases in digoxin levels
    • Prednisolone - false increases in digoxin levels
    • Prednisone - false increases in digoxin levels
    • Progesterone - false increases in digoxin levels
    • Spironolactone - false increases in digoxin levels
    • Tan-Shen - false increases in digoxin concentrations
    Test Tube Needed
    • Heparin or EDTA tube
    Procedure
    • In the outpatient setting, patients should not exercise for at least 1 hour prior to sample collection. 
    • Collect venous blood specimen 8 to 12 hours after last dose or prior to next dose.
    Storage and Handling
    • Store sample at 2°C to 8°C for up to 24 hours or at -20°C for 1 to 2 weeks.
    What To Tell Patient Before & After
    • None
    References
    • Eichhorn EJ et al. Digoxin - new perspective on an old drug. N Engl J Med 2002;347:1394-5.
    • LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.

MESH Terms & Keywords

  • Digoxin Level, Dig Level, Digoxin Blood Level