Plantaginaceae
Digitalis purpurea
Foxglove · Common foxglove · Fairy thimbles
- Part used
- leaf
- Native range
- Western and southwestern Europe, naturalised widely in temperate regions including Australia and New Zealand
- Morphology
- Biennial. A rosette of soft grey-green leaves in the first year, then a one-sided spike to about two metres bearing tubular purple flowers spotted inside.
- Also known as
- Digitalis tomentosa
What is in it
Evidence
The isolated glycoside digoxin has been used in heart failure and atrial fibrillation for two centuries and remains in the pharmacopoeia, though its role has narrowed considerably as better drugs arrived. The plant itself has no place in modern practice, and the distinction matters — the drug is dosed to the microgram and the leaf is not.
Safety
Acutely and potentially fatally cardiotoxic. The margin between an effective and a toxic dose is famously narrow, and toxicity is cumulative because the glycosides are slowly cleared. Poisoning presents as nausea and vomiting, confusion, disturbed colour vision with yellow-green haloes, and progressive bradycardia and arrhythmia. Accidental poisonings occur from mistaking the first-year rosette for comfrey and from drinking water in which cut stems have stood.
Interactions: Additive toxicity with anything that lowers potassium, including many diuretics; Serious interaction risk with calcium, quinidine, amiodarone, verapamil and macrolide antibiotics
Regulatory: Not permitted as a listed medicine ingredient. Digoxin is a prescription-only medicine in Australia and comparable jurisdictions.
How the traditions classify it
Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.
Historical use
A folk remedy for dropsy in the English west midlands. William Withering learned of a family recipe in Shropshire in 1775, identified foxglove as the active ingredient among some twenty herbs, and published his account in 1785 after ten years of clinical observation.
Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.
Worth knowing
Withering did not simply adopt the Shropshire recipe. He gave foxglove to 163 patients over a decade, recorded the failures alongside the successes, and worked out that the plant part, the drying method and the harvest time all changed its strength. He also documented the toxicity carefully enough that his description of yellow-green visual disturbance is still the textbook sign of digitalis poisoning.
The colour vision detail has a famous and probably untrue coda. Van Gogh's yellow period has repeatedly been attributed to digitalis prescribed for epilepsy, partly on the strength of his two portraits of Dr Gachet holding a foxglove sprig. There is no evidence he was ever given it, and art historians regard the theory as a good story rather than a finding.
Nomenclature verified against GBIF backbone taxonomy.