Digoxin

Question 1

Therapeutic Range

Answer 1

Therapeutic Range: 0.8 to 2 mcg/L (wide interindividual variations.
Loading doses may be required

Question 2

Monitoring

Answer 2

Serum electrolytes (K+, Mg2+, Ca2+) as electrolyte imbalance (hypokalaemia, hypomagnesaemia,
hypercalcaemia) can potentiate toxicity, renal function, heart rate (maintained at greater than 60
beats per minute)

Question 3

Major Route of Elimination

Answer 3

Renal excretion, Hepatic metabolism to active metabolites

Question 4

Warning signs

Answer 4

• Cardiac e.g. arrhythmias, heart block
• Neurological e.g. weakness, lethargy, dizziness, headache, mental confusion, pyschosis
• Gastrointestinal e.g. anorexia, nausea, vomiting, diarrhoea, abdominal pain
• Visual e.g. blurred and/or yellow vision

Question 5

Actions Required

Answer 5

• Advise patient to report immediately to a doctor if any warning signs occur
Note: Dosage forms have different bioavailabilities (change of dose required to maintain same
plasma-digoxin concentration). Please refer to manufacturer Summary of Product Characteristics
for more information.
• Intravenous: 100%
• Tablet: 50-90%
• Elixir: 75%

Question 6

Interactions

Answer 6

• Increased plasma concentration with alprazolamamiodarone, ciclosporin, diltiazem,
itraconazole, lercanidipine, macrolides, mirabegron, nicardipine, nifedipine, quinine,
spironolactone and verapamil
• Reduced plasma concentrations with St. John’s Wort
• Concomitant administration of acetazolamide, amphotericin, loop diuretics or thiazides and
related diuretics can cause hypokalaemia that increases the risk of cardiac toxicity and digoxin
toxicity
• Drugs that impair renal function can affect the plasma digoxin concentration e.g. NSAIDs,
ACE inhibitors