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Atrial fibrillation - Management
How should I monitor someone taking digoxin?

  • Digoxin has a narrow therapeutic window, and measurement of serum levels may be considered in the following instances:
    • Shortly after initiation, to check that drug levels are in the correct therapeutic range (not standard practice).
    • When there is a dose change.
    • When there are adverse effects suggestive of overdosing.
    • When there are factors that may affect digoxin serum levels, such as use of a concomitant drug that affects digoxin serum levels, or deteriorating renal function.
    • When noncompliance is suspected.
  • The therapeutic range of digoxin is between 0.7 nanograms/mL and 2.0 nanograms/mL.
    • Blood samples should be taken at least 6 hours after the previous dose, but ideally 8–12 hours afterwards.
    • Monitoring should be performed several days after the last dose change.
  • The likelihood of toxicity depends on the serum concentration of digoxin.
    • Levels less than 1.5 nanograms/mL in the absence of hypokalaemia indicate that digoxin toxicity is unlikely.
    • Levels greater than 3.0 nanograms/mL indicate that digoxin toxicity is likely.
    • With levels between 1.5 nanograms/mL and 3.0 nanograms/mL, digoxin toxicity should be considered a possibility.
  • In addition, blood chemistry measurements (electrolytes, urea, and creatinine) should be done at least annually. These tests will often be done routinely, as renal function is likely to be monitored owing to the use of nephrotoxic drugs (such as diuretics and drugs affecting the renin-angiotensin system).
Basis for recommendation
  • These recommendations are taken from the National Institute of Health and Clinical Excellence guidance Chronic heart failure: management of chronic heart failure in adults in primary and secondary care [NICE, 2003].

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