heart failure and atrial fibrillation · reviewed 2026-08-01
Digoxin and foxglove: a plant molecule made measurable at a very narrow margin
Digoxin is a cardiac glycoside obtained from woolly foxglove. Purification does not make it gentle; it makes an exact, narrow-therapeutic-index molecule measurable while whole foxglove remains an unpredictable and potentially fatal mixture.
Defined medicine
digoxin
Digitalis glycoside
Where it came from
Digoxin is the same cardiac glycoside isolated from Digitalis lanata leaves. It is a natural product medicine, not a synthetic imitation of foxglove. digoxin-label
What it is trying to achieve
Digoxin has labelled roles in selected heart-failure and atrial-fibrillation settings. In the major heart-failure trial it reduced hospitalisation for worsening heart failure without reducing overall mortality. digoxin-label dig-trial
How it acts
Digoxin inhibits sodium-potassium ATPase, increasing intracellular calcium in cardiac muscle, and increases vagal influence on atrioventricular conduction. The same actions can become toxic when exposure rises. digoxin-label
Why people developed this form
Isolation, assay, and pharmaceutical formulation produced a named glycoside with assayed strength. Its absorption and renal clearance could be characterised, blood concentrations monitored, and interactions studied and managed. digoxin-label foxglove-poison
Present form and manufacture
Tablets, oral solution, and injection have different concentration and systemic-availability characteristics. Product-specific calculations and monitoring exist because small exposure changes can matter. digoxin-label
Bioavailability
The label reports incomplete and formulation-dependent oral bioavailability, extensive tissue distribution, and predominantly renal elimination. Kidney function, age, body composition, and interacting medicines can change systemic exposure. digoxin-label
Its own risks
Digoxin has a narrow therapeutic index. Toxicity can include nausea, confusion, visual disturbance, dangerous bradycardia or arrhythmia, and death; electrolyte disturbance, renal impairment, and interactions increase risk. digoxin-label foxglove-poison
What nature offers
No link below is assumed to be equivalent. Each names the organism or tradition, exact preparation, measured exposure, human evidence, and replacement boundary separately.
Nature link · Same molecule occurs in nature
woolly foxglove
Digitalis lanata
foxglove · Digitalis leaf
- Exact material
- Living plant or crude Digitalis leaf containing a shifting mixture of cardiac glycosides; this entry supplies lineage and poisoning context, not a usable herbal preparation. digoxin-label foxglove-poison
- Relationship
- Same molecule occurs in nature. Chemical identity may match, but purity, amount, formulation, route, companion compounds, and evidence can still differ.
Lineage
Digitalis lanata is the botanical source of digoxin. Other foxglove species and plant parts contain differing cardiac glycosides, so the common name does not specify a digoxin amount. digoxin-label foxglove-poison
Traditional context
Foxglove's medical history preceded modern assays, but historical use cannot supply the identity, purity, exposure, electrocardiographic observation, renal assessment, and interaction control attached to digoxin. digoxin-label foxglove-poison
Human evidence
Evidence of harm Evidence product match: not applicable
Whole-plant ingestion is documented poisoning, not a validated way to deliver digoxin. Clinical outcome evidence for pharmaceutical digoxin cannot be transferred to leaves containing multiple uncertain glycosides. foxglove-poison dig-trial
Bioavailability and preparation
There is no safe bioequivalence bridge from leaf mass or a homemade extract to a labelled digoxin formulation. Glycoside content varies and the therapeutic-to-toxic separation is too narrow for crude material. digoxin-label foxglove-poison ema-herbal-biopharm
Safety
All parts of foxglove can poison. Cardiac glycoside toxicity may produce gastrointestinal, neurologic, electrolyte, conduction, and lethal rhythm effects; visual plant identification does not control chemical exposure. foxglove-poison
Can it replace the medicine?
The plant is the source of the molecule and is not a clinical substitute for purified, assayed digoxin; whole foxglove is a poisoning hazard. digoxin-label foxglove-poison
The honest comparison
Digoxin refutes the idea that 'synthetic medicine' is the only source of pharmaceutical danger: this drug is natural, clinically useful in selected settings, and intrinsically toxic near therapeutic exposure. digoxin-label dig-trial
Purification did not improve on nature by making digoxin stronger; foxglove was already potent. It made one molecule identifiable and monitorable enough to study while exposing why the whole plant is unsafe. digoxin-label foxglove-poison
Sources for this card
- Digoxin prescribing information US National Library of Medicine DailyMed · regulatory label · read 2026-08-01
- The effect of digoxin on mortality and morbidity in patients with heart failure PubMed · primary research · read 2026-08-01
- Foxglove poisoning US National Library of Medicine MedlinePlus · official guidance · read 2026-08-01
- Points to consider on the biopharmaceutical characterisation of herbal medicinal products European Medicines Agency · official guidance · read 2026-08-01
Same card as data: /api/remedies/digoxin-foxglove.json. Found a source or claim problem? Open a correction.