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Digitalis spp., foxglove

Summary

A very common plant, both in the garden and the wild, with the potential to kill in quite small amounts but also the source of medication which has saved thousands of lives since its discovery in 1775.

Digitalis spp., foxglove

Digitalis purperea, foxglove

Family

Scrophulariaceae

Meaning of the Name

Digitalis
From ‘digitus’, Latin for ‘finger’ after the fingertip like flowers.
 
ferruginea
From ‘ferruginis’, the colour of iron rust.

lantana
possibly after the genus Lantana or may be related to 'lentus' meaning 'flexible'
 
purpurea
purple

Common Names and Synonyms

foxglove, dead men's bells, dog's finger, fairy fingers, fairy gloves, finger flower, folk's glove, lion's mouth, ladies' glove

How Poisonous, How Harmful?

Contains cardiac glycosides called digitoxin, digitalin, digitonin, digitalosmin, gitoxin and gitalonin. During digestion these produce aglycones and a sugar. The aglycones directly affect the heart muscles.

It produces a slowing of the heart which, if maintained, usually produces a massive heart attack as the heart struggles to supply sufficient oxygen to the brain. The acceleration of the heart ahead of this, sometimes leads to it being wrongly said to increase the heart rate.

The raw plant material is, however, emetic and eating a large amount may produce vomiting thus expelling the cardiac poisons before they can do serious harm.

Watch a Short Video

This three minute video has a soundtrack extracted from a 'Lethal Lovelies' talk given in November, 2008.

For more information on talks about poison plants, go to the 'Talks' page.

Incidents

In April 2010, Lisa Leigh Allen of Denver Colorado entered a plea of guilty to felony assault as part of a plea bargain agreement. She had been accused of attempted murder after a meal of spaghetti and salad, fed to her husband, was found to have foxglove leaves in the salad. She was sentenced to four and a half years in jail.

Her husband, who required hospital treatment for severe gastrointestinal upset and heart problems, apparently thought the salad tasted unusually bitter but assumed it was just one of those fashionable herb leaves which seem to appear from time to time.

Digitalis at the rosette stage

A young plant showing the similarity of the
leaves to other plants

In 2005, an amateur botanist committed suicide by eating foxglove leaves. Knowing of their emetic effect, he limited his consumption to two leaves. It was twenty-four hours later before he suffered a fatal heart attack.

A retired hospital pharmacist told of a young man admitted to hospital after making himself a ‘herb’ quiche using foxglove leaves. His heartbeat became extremely slow and, for a couple of days, it was impossible to measure the digitalis level in his bloodstream as it was far above the maximum which the instruments could record. It took several days of intensive care for the level to subside and his heart rate to return to normal.

There are a number of instances of poisoning as a result of drinking herbal tea mistakenly made with foxglove leaves. Generally, the confusion appears to arise with Symphytum leaves.

In 2006, Charles Cullen was sentenced to multiple terms of life imprisonment in the USA after confessing to 29 murders of patients at hospitals where he worked as a nurse. His preferred weapons were lethal injections of digoxin or insulin. He may have killed another 11 but, it seems, their illnesses may have killed them before the injections could have an effect.

Folklore and Facts

John Gerard said of foxgloves ‘They are of no use, neither have they any place amongst medicines, according to the Ancients.’ It was the 18th century before the therapeutic properties of the foxglove were documented.

In 1775, Dr. William Withering was asked to comment on a family recipe for the treatment of dropsy which had come from an old woman in a village in Shropshire. Dropsy, a condition where the soft tissue swells due to an increase in fluid retention was, at the time, treated symptomatically. That is, diuretics were used to remove the fluid. It is now known that congestive heart failure results in a build up of fluid in the lungs as well as the soft tissue. Withering’s early experiments with foxglove were performed on poor patients who attended a weekly two hour free clinic which he offered and, in seeking to use the plant as a diuretic he, by his own admission, achieved little success.

He was inclined to give up his work with the foxglove when he heard from his friend, a Dr. Ash, that the principal of Brazen Nose (now called Brasenose) College, Oxford had been cured of Hydrops Pectoris, a sort of dropsy of the lungs, by means of the root of the foxglove. When Withering was able to obtain a supply of dried leaves, giving him the chance to measure dosage more accurately, he embarked on a series of trials all of which he set down in detail, even those which failed.

By 1785, when his ‘An Account of the Foxglove’ was published, Withering had demonstrated the benefit of using foxglove to treat dropsy even though he assumed its success to be based on its properties as a diuretic rather than having a direct cardiac effect.

Digitalis spp., foxglove

Digitalis purperea 'Alba'



Withering’s place in the history of the development of medicine relies on three things; his willingness to look at a folk remedy to see if it had any merit when most of his contemporaries would have scorned such an enquiry, his lack of vanity in publishing all of his trial results even those which indicated failures in his treatment of patients, but his greatest legacy is much more general than just the use of the foxglove.

At some point in his work, Withering had what may be described as an ‘Emperor’s New Clothes’ moment. He realised that there was nothing about the look of Digitalis which would lead you to conclude that it could be used to treat dropsy and, against the then conventional wisdom, concluded that the Doctrine of Signatures was without merit. This revelation freed doctors from the bounds of only looking for remedies from plants which met the criteria of the Doctrine of Signatures and, I believe, began a much more rationally based investigation of disease and its treatment.

There are a number of explanations offered for the name 'foxglove'. It is said that it was originally named 'folk's love' meaning the fairies loved the way the flowers point downwards as it gives them a place to shelter. As home to the fairies, children were told it was bad luck to disturb the plant as this would lead to the fairies being homeless.

It is also said to come from 'fox glove' as the fairies gave the flowers to foxes to wear as gloves so as to leave no trace when raiding a hen house. This explanation was popular with people inclined to raid the rich man's hen house for themselves.

Numerous people have told me about playing with the flowers of foxgloves, as children, without coming to any harm but you will still see alleged experts saying that it should be removed from any place where children might be present.

Digitalis lantana is the species grown commercially for pharmaceutical use.