A cardiac glycoside (heart medicine)
Digoxin
A long-established heart medicine that slows a fast pulse in atrial fibrillation and can help some people with heart failure — used carefully because the safe range is narrow.
What is Digoxin?
Digoxin is a cardiac glycoside used to slow a fast heart rate in atrial fibrillation and to help symptoms in some people with heart failure. It strengthens the heart's contraction and slows conduction through the heart. It has a narrow safe range, so levels, kidney function and potassium are monitored, and signs of toxicity (nausea, visual changes, a slow or irregular pulse) are taken seriously.
Education and reference only. This is a plain-language guide to Digoxin — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Digoxin is one of the oldest heart medicines still in regular use, originally derived from the foxglove plant. It has two main roles: slowing down a fast heart rate in atrial fibrillation (especially in people who are less active or who also have heart failure), and improving symptoms in some people with heart failure. It is taken as a long-term daily tablet. Its usefulness is balanced by a narrow margin between a helpful amount and too much, so it is used thoughtfully and monitored.
How it works
Digoxin works in two complementary ways. It increases the force of each heartbeat by raising the calcium available inside heart-muscle cells, which can help a weak, failing heart pump more effectively. At the same time it increases the activity of the vagus nerve, slowing the electrical signals passing through the heart's "junction box" (the AV node); this is what slows a fast pulse in atrial fibrillation. Because it is cleared by the kidneys and works within a narrow range, the right amount depends on kidney function and body size.
What it treats
Conditions Digoxin is used for
Practical use
How to take Digoxin
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it at the same time each day, exactly as prescribed; the amount is tailored to you and your kidney function.
- Report early warning signs of toxicity: nausea, loss of appetite, unusual tiredness or confusion, visual changes (yellow-green halos), or a slow or very irregular pulse.
- Do not start or stop other medicines — especially water tablets (diuretics) — without advice, as they can change your potassium and your digoxin level.
- Stay well hydrated during illness, as dehydration can raise digoxin levels; tell your doctor if you have vomiting or diarrhoea.
- If you miss a dose, do not double up; take the next dose as usual.
Weighing it up
Advantages & disadvantages of Digoxin
Advantages
- Long experience, low cost, and can be used in people with heart failure.
- Helpful for rate control in atrial fibrillation, particularly in less active people or alongside other rate-slowing medicines.
- Does not lower blood pressure, so it can suit people who cannot tolerate other rate-controlling drugs.
Disadvantages
- Narrow safe range with a real risk of toxicity, needing monitoring of kidneys and potassium.
- Interacts with several common medicines (amiodarone, verapamil, some antibiotics) that raise its level.
- Less effective at controlling heart rate during exertion than some alternatives.
Practical use
Good to know
Digoxin has a narrow therapeutic range, meaning the difference between a helpful level and a toxic one is small. Early signs of too much include feeling sick, going off food, tiredness, confusion, and visual changes such as seeing yellow-green halos around lights — these should be reported. A low blood potassium level (which can be caused by common water tablets/diuretics) makes toxicity more likely, so potassium is kept in check. Because it is removed by the kidneys, dehydration or worsening kidney function can allow levels to climb. Blood levels can be measured when toxicity is suspected.
Who should not take it / use with caution
- People with certain heart-rhythm or conduction problems (such as some types of heart block without a pacemaker) or specific ventricular arrhythmias.
- Used cautiously and at reduced amounts in people with impaired kidney function or low body weight, and in older people.
- People with a low potassium or magnesium level until this is corrected, as it increases the risk of toxicity.
Monitoring
- Kidney function and potassium (and magnesium) levels
- Heart rate and rhythm
- Digoxin blood level when toxicity is suspected or the picture is unclear
Side effects
- When levels are right, often none. Digestive upset (nausea, loss of appetite) can be an early sign the level is climbing.
- Signs of toxicity: worsening nausea, tiredness, confusion, visual disturbances (blurring or yellow-green halos), and a slow or irregular pulse — report these promptly.
- Rarely, new abnormal heart rhythms, which is part of why levels and potassium are monitored.
Key interactions
- Amiodarone, verapamil, and some antibiotics (such as clarithromycin and erythromycin) raise digoxin levels and the risk of toxicity — the amount is often reduced.
- Water tablets (diuretics) that lower potassium increase the risk of toxicity; potassium-sparing medicines and supplements need balancing.
- Anything that reduces kidney function or causes dehydration can push levels up.
Available as: Tablets; also a liquid and an injection (the latter used in hospital).
Answers
Digoxin: frequently asked questions
What are the warning signs of digoxin toxicity?
Feeling sick, losing your appetite, unusual tiredness or confusion, and visual changes — classically seeing yellow-green halos around lights — can all signal that the level is too high, as can a slow or very irregular pulse. Report these promptly; a blood test can measure the level.
Why does my potassium matter on digoxin?
A low blood potassium makes digoxin toxicity much more likely, even at normal levels. Because common water tablets (diuretics) can lower potassium, your potassium is checked and kept in range, and you should not change diuretics without advice.
Does digoxin lower blood pressure?
No — unlike many heart medicines, digoxin does not lower blood pressure. That can make it a useful option for people whose blood pressure is already low or who cannot tolerate blood-pressure-lowering rate-control drugs.
Is Lanoxin the same as digoxin?
Yes — digoxin is the generic (active-ingredient) name and Lanoxin is a brand name; both contain the same active ingredient.
Authoritative sources
- BNF: Digoxin.
- electronic Medicines Compendium (SmPC): Digoxin (Lanoxin).
- NICE CKS: Atrial fibrillation; Heart failure – chronic.
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