Cardiovascular
Digoxin
A cardiac glycoside — An old but useful drug for atrial fibrillation and heart failure — with a narrow safety margin.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
Digoxin is used to slow and control the heart rate in atrial fibrillation — particularly in less active or older patients — and as an add-on in some heart failure to ease symptoms. It is one of the oldest cardiac drugs still in regular use.
How it works
It increases the force of each heartbeat and, through its effect on the heart's conducting tissue and the nervous system, slows conduction through the AV node — which is what brings down a fast ventricular rate in atrial fibrillation. These same actions on the heart's electrics are why excess digoxin causes dangerous rhythm disturbances.
In practice
In practice digoxin's defining feature is its narrow therapeutic window: the gap between an effective level and a toxic one is small, so it demands respect. It is cleared by the kidneys, so falling renal function or dehydration can quietly push levels into the toxic range, and low potassium (often from diuretics) makes the heart far more sensitive to it — a classic, dangerous combination. Toxicity is easy to miss because the early signs are vague (nausea, poor appetite, tiredness, confusion in the elderly, and visual disturbance such as seeing haloes or a yellow-green tinge), progressing to serious arrhythmias. Levels are checked when toxicity is suspected or after dose changes, sampled at the right time after a dose. Amiodarone and several other drugs raise digoxin levels, so co-prescribing usually means a dose reduction and closer monitoring.
Examples
Practical use
How to take it & use it well
- Take digoxin once a day at the same time, with or without food, exactly as prescribed.
- This medicine has a narrow safety margin, so never change the dose or take extra without medical advice.
- Have the blood tests your clinician arranges, including kidney function and sometimes a digoxin level, as these guide safe dosing.
- Learn the warning signs of too much digoxin - feeling sick, being off your food, confusion, or seeing yellow-green halos or blurred vision - and report them promptly.
- Keep your potassium in a healthy range; tell your clinician if you start fluid tablets, vomit a lot, or have prolonged diarrhoea, as these can upset the balance.
Common uses
- Rate control in atrial fibrillation (especially sedentary/elderly patients)
- Symptom relief in selected chronic heart failure
Monitoring
- Renal function and potassium (and magnesium)
- Digoxin level when toxicity is suspected or after dose/renal changes (timed correctly after the dose)
- Heart rate and symptoms
Weighing it up
Advantages & disadvantages
Advantages
- Helps control a fast, irregular heartbeat and can ease symptoms of heart failure.
- Can improve breathlessness and exercise tolerance in some people with heart failure.
- Long experience of use means its effects and risks are well understood.
Disadvantages
- The gap between a helpful and a toxic amount is small, so careful dosing and monitoring are essential.
- Toxicity is more likely if the kidneys are not working well or potassium is low.
- Early signs of toxicity, such as nausea, tiredness, confusion or visual changes, can be easy to miss.
- Many common medicines and changes in body salts can push levels into the toxic range.
Key safety principles
What to watch for
- Narrow therapeutic margin — toxicity can develop from declining renal function, dehydration or interacting drugs.
- Low potassium (and low magnesium) greatly increase toxicity risk — relevant with diuretics.
- Toxicity signs are easily missed: nausea, confusion, visual changes (haloes/yellow-green vision) and arrhythmias.
Key interactions
What to avoid or check alongside
- Amiodarone and verapamil: raise digoxin levels and the risk of toxicity.
- Diuretics (water tablets): can lower potassium, which makes digoxin toxicity more likely.
- Some antibiotics (such as clarithromycin): can increase digoxin levels.
- Medicines that affect the kidneys (such as NSAIDs): reduced kidney function can let digoxin build up.
- Spironolactone: can affect digoxin levels and potassium balance.
Patient & carer advice
- Report nausea, loss of appetite, confusion or changes in your vision
- Keep up with blood tests, especially if your kidney tablets or water tablets change
- Tell us before starting new medicines — several interact with digoxin
Use with
Related clinical calculators
Dose and risk decisions for this class often depend on renal function, weight or bleeding/stroke risk. These tools help:
Answers
Digoxin: frequently asked questions
What are the warning signs of digoxin toxicity?
Feeling sick, losing your appetite, vomiting, unusual tiredness or confusion, a slow or irregular pulse, and seeing yellow-green tints, halos or blurred vision. If these occur, contact your clinician promptly as your level may be too high.
Why does my potassium matter on digoxin?
Low potassium makes the heart more sensitive to digoxin and increases the risk of toxicity. Water tablets, vomiting or diarrhoea can lower potassium, so tell your clinician if these affect you.
Why are my kidneys checked while taking digoxin?
Digoxin is largely cleared by the kidneys. If kidney function falls, the drug can build up to harmful levels, so kidney blood tests help keep your dose safe.
Can I take ibuprofen with digoxin?
Anti-inflammatory painkillers like ibuprofen can reduce kidney function and let digoxin build up. Check with a pharmacist or doctor before using them, especially regularly or if you also take water tablets.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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