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Using this page · Individualise medicines monitoring

This medicines monitoring page has been written using publications and expert opinion. It is designed to save clinician time, but not replace professional responsibility. When using this page you should: ensure an individualised monitoring plan is developed in partnership with the patient and take account of any locally agreed advice and guidance.

Before starting

Required

  • Baseline
    • Serum calcium
    • Serum creatinine (for creatinine clearance)
    • Serum magnesium
    • Serum potassium
    • Thyroid function testsdigoxin may require dose amendment in thyroid disease
    • Urea and electrolytes

Ongoing once stable

Required

  • Annually
    • Serum calcium
    • Serum creatinine (for creatinine clearance)
    • Serum magnesiumincreased frequency may be required if long-term PPI, other medicine pre-disposing to hypomagnesaemia, or low calcium level
    • Serum potassium
    • Urea and electrolytes

Increase frequency in elderly or renal impairment

More frequent monitoring may be required in elderly people and people with renal impairment.

Consider

  • Periodically in specific circumstances
    • Serum digoxin concentrationtaken no less than 6 hours (ideally 8-12 hours) after last dose

When to take a digoxin level

Routine monitoring of serum digoxin is not recommended; however, consider checking serum digoxin levels in the following circumstances:

  • Patient has experienced adverse effects suggestive of toxicity (such as confusion, nausea, anorexia, or disturbance of colour vision).
  • Other factors may affect the digoxin level, such as the use of a concomitant drug (for example amiodarone, diltiazem, or verapamil), deteriorating renal function, thyroid disease, and advancing age.
  • Poor adherence is suspected.

Abnormal results

Digoxin toxicity

Normal and abnormal serum digoxin concentrations

The therapeutic range for serum digoxin concentration is between 0.7 nanograms/mL and 2.0 nanograms/mL. The concentration can thus determine the likelihood of toxicity; in particular:

  • Levels less than 1.5 nanograms/mL in the absence of hypokalaemia indicate that digoxin toxicity is unlikely.
  • Levels between 1.5 nanograms/mL and 3.0 nanograms/mL, digoxin toxicity should be considered a possibility.
  • Levels greater than 3.0 nanograms/mL indicate that digoxin toxicity is likely.

Be mindful of clinical signs of toxicity

However, digoxin toxicity can also occur when the serum digoxin concentration is within the therapeutic range. Therefore always interpret results in the clinical context. The presence of the following toxic symptoms may prompt an urgent measurement:

  • Nausea and vomiting
  • Visual disturbance (yellow-green discolouration)
  • Severe dysthymias

Managing toxicity

If toxicity occurs, digoxin should be withdrawn. Serious manifestations require urgent specialist management. Digoxin-specific antibody fragments are available for reversal of life-threatening overdosage.

Electrolyte imbalances

Hypokalaemia, hypomagnesaemia, and hypercalcaemia predispose the patient to digoxin related problems and hypokalaemia and hypomagnesaemia should be corrected either orally or intravenously, as appropriate.

Hypocalcaemia may indicate that magnesium levels are also low.

Thyroid function

Initial and maintenance doses of digoxin should be amended when thyroid function is abnormal.

Hypothyroidism

Hypothyroidism may require a reduction is digoxin dose.

Hyperthyroidism

Hyperthyoidism can lead to relative digoxin resistance, and the dose may have to be increased.

Treatment of thyrotoxicosis

During the course of treatment of thyrotoxicosis, dosage should be reduced as the thyrotoxicosis comes under control.

Bibliography

Enquiries about this page

Contact us if you have any enquiries about the drug monitoring information on this page.