X
More than 60,000 patients use Brite
4.6 stars
Your health finally understandable with Brite
Enter email and you're done. No subscription, no credit card.
Search, tap and you're done. Over 3,400 medicines.
Check, remind, get an overview.
Sarah K., 34
I finally understand my therapy. The app reminds me, answers my questions — and I don't feel alone with it anymore.
Digitoxin is a cardiac glycoside from the foxglove plant that slows the pulse in atrial fibrillation and supports the heart’s pumping power in heart failure. There is only a narrow window between an effective and a toxic dose, and the half-life is around one week. That is why level checks, a stable potassium value and recognising early signs of toxicity such as nausea or yellow vision are crucial.
See more detail.gif)
Digitoxin is broken down via the liver enzyme CYP3A4 and is influenced by the transport protein P-glycoprotein. Interactions also arise via potassium balance and via medicines that slow the pulse further. The SmPC advises thinking of possible interactions with every additional treatment and checking the level if in doubt.¹
| Combination | Consequence | What to do |
|---|---|---|
| Calcium given as an injection into a vein | Increased toxicity | Contraindicated — inform the emergency team |
| Potassium-lowering medicines: diuretics such as furosemide, torasemide or hydrochlorothiazide, excessive use of laxatives, corticosteroids such as prednisolone, amphotericin B | Potassium and magnesium deficiency, risk of toxicity | Check potassium and magnesium regularly |
| Antiarrhythmics such as amiodarone or quinidine | Digitoxin levels rise, pulse and conduction slowed further | Dose and level adjusted by a doctor |
| Calcium channel blockers such as verapamil, diltiazem, nifedipine | Digitoxin levels rise; verapamil and diltiazem also slow the pulse further | Check level and pulse |
| Macrolide antibiotics such as clarithromycin, tetracyclines, itraconazole, certain HIV medicines, fluoxetine | Digitoxin levels rise | Mention digitoxin when they are prescribed, watch for signs of toxicity |
| Beta blockers such as bisoprolol or metoprolol | Stronger slowing of the pulse | A common and useful combination, but keep an eye on your pulse |
| Potassium-raising medicines: spironolactone, amiloride, triamterene, potassium supplements | Weaker effect, rhythm disorders if potassium is too high; spironolactone can also interfere with the level test and lower the level | Check potassium; have lab values interpreted together |
| Colestyramine, colestipol, activated charcoal, kaolin-pectin, some bulk-forming laxatives | Less absorption, faster elimination | Take digitoxin two hours beforehand |
| Enzyme inducers: rifampicin, phenytoin, phenobarbital and other barbiturates | Digitoxin levels fall, the effect wears off | Check the level — also after the inducer has been stopped, as it will then rise again |
| Theophylline, sympathomimetics, tricyclic antidepressants, certain muscle relaxants used in anaesthesia | Rhythm disorders are promoted | Weigh up with a doctor; inform the anaesthesia team before operations |
The most treacherous combination in everyday life is the one with water tablets: in heart failure they are almost always part of the treatment, and especially after a dose increase or with additional diarrhoea, potassium can fall unnoticed. A second trap is antibiotics: some raise the level by inhibiting enzymes or transporters, others because they wipe out gut bacteria that break down part of the digitoxin in some people.¹ After a week of antibiotics, nausea is therefore easily blamed on the infection — and yet it may be the level.
The SmPC does not list a specific interaction with alcohol; larger amounts can, however, play an indirect role via vomiting, diarrhoea and potassium balance, and they put additional strain on the heart in atrial fibrillation. With every new prescription — including over-the-counter laxatives and herbal products — it is worth taking a look at the interaction check. The basics are in the guide drug interactions.
Digitalis is one of the oldest heart medicines and was controversial for a long time. With beta blockers, angiotensin receptor-neprilysin inhibitors such as sacubitril/valsartan, mineralocorticoid receptor antagonists and SGLT2 inhibitors such as empagliflozin, medicines are available today that improve survival in heart failure. In the guidelines, digitalis is regarded as a possible addition if symptoms remain despite this basic treatment, or for rate control in atrial fibrillation.⁴
The DIGIT-HF trial, led from Germany, studied digitoxin in addition to guideline-based treatment in more than 1,200 people with symptomatic heart failure and markedly reduced pumping function. Treatment started at 0.07 mg daily and was adjusted to a low target level. Over an average follow-up of three years, the combined endpoint of death or hospital admission for heart failure occurred less often on digitoxin than on placebo (39.5 versus 44.1 per cent). The individual components — death and hospital admission — were not significantly reduced on their own.³
To put it honestly: this is a moderate but relevant benefit, achieved with low dosing and regular check-ups. It is not a licence for high levels and no substitute for the other heart failure medicines.
| Feature | Digitoxin | Digoxin |
|---|---|---|
| Breakdown | Mainly in the liver, circulation between liver and gut; excreted via the kidneys and stool | Mainly excreted unchanged via the kidneys |
| Half-life | Around one week | Much shorter, prolonged in kidney impairment |
| In kidney impairment | Elimination hardly changed, as the liver and gut compensate | The dose must be adjusted to kidney function |
| After an overdose | Effects last particularly long | Wears off more quickly |
| Use | Mainly used in Germany | International standard |
According to the SmPC, impaired kidney function alone has hardly any influence on the elimination of digitoxin; higher levels are only to be expected with combined liver and kidney impairment.¹ This is a real advantage in chronic kidney disease and in older age. Nevertheless, the SmPC names impaired kidney function as one of the most common triggers of digitalis toxicity — the kidneys still play a role via potassium, fluid and accompanying medicines.
Yes, this is actually one of the most important early warning signs. According to the SmPC, nausea on digitoxin should be regarded as a sign of too high a dose. Of course, an infection may also be behind it — but a stomach bug in particular lowers potassium and can push the level into the critical range. So contact the practice promptly and have your level and potassium measured instead of waiting. If vision problems, confusion or an irregular, slow pulse are added, it is an emergency.
Altered colour vision in the yellow-green range is a known side effect of digitalis and, according to the SmPC, can occur even at levels within the target range. It is still a signal that should be assessed by a doctor promptly, because it can also point to a level that is too high. Have other causes considered as well: visual disturbances have many causes, such as cataracts.
Because the level is only half the story. With low potassium, low magnesium, high calcium, an underactive thyroid or lack of oxygen, the heart reacts more sensitively, so signs of toxicity can occur even with an unremarkable level. In addition, other glycosides or spironolactone can interfere with the test. The practice therefore always assesses the overall picture: symptoms, ECG, potassium, kidney function and level.
Because of the long half-life, the level only falls gradually after a few missed days — but that is not a licence to take a break. Report a shortage early so that the practice and pharmacy can find a solution in good time, for example a delivery from abroad or a planned switch. Never swap digitoxin yourself for digoxin or for tablets from an old pack from a different manufacturer unless the dose and the switching break have been set by a doctor.
The interaction check reviews your whole list for potassium and level traps.
