Foxglove

In The Colour of Murder I feature the use of digitalis, a toxin present in all parts of the foxglove plant, though different species are poisonous to varying degrees. Foxgloves are such attractive flowers that they have been grown in gardens for centuries, despite the danger. Today, digitalis is still used in medicine for the treatment of certain heart conditions in the form of the drug digoxin. Digitalis causes slower, more intense contractions of the heart and may make it beat irregularly – it is these accentuated effects which are the causes of death. Nausea and loss of appetite are other side effects but all these symptoms could be attributed to ‘natural causes’ rather than poisoning. The side effect that was most noticeable for Seb Foxley in The Colour of Murder was that of visual distortion. Digitalis causes colour-vision changes, making everything appear greenish yellow, sometimes with mistiness or ‘snow’. Lights may seem to flicker or have haloes. I took liberties in having Seb suffer these visual problems after a single dose: patients on digoxin treatment don’t usually notice such aberrations until a few weeks after they begin to take the pills.
It is possible that Vincent van Gogh may have been taking digitalis in his later years, perhaps as a treatment for his epilepsy, although it wouldn’t have helped this condition. It would certainly explain his ‘yellow period’ and the haloes around the stars in his famous ‘Starry Night’ painting. His two portraits of his doctor both include foxglove flowers which might be another clue.
In case of an overdose of digitalis, another equally toxic substance provided the antidote: atropine from the deadly nightshade plant. Atropine causes the heart rate to increase so counters the effect of digitalis but, administered alone in a high dose, the accelerated heart rate and resultant high blood pressure can kill. Atropine was used as a cosmetic product in medieval Italy because, as a side effect, it causes the pupils to dilate, making the eyes appear larger and more striking – hence its other name ‘belladonna’ or ‘beautiful lady’. Unfortunately, even quite small doses administered as drops into the eye can cause hallucinations for up to twelve hours as well as a sense of disorientation. I wonder if it was worth it just to enhance a lady’s eyes.

Symptoms of Digitalis poisoning include a low pulse rate, nausea, vomiting, and uncoordinated contractions of different parts of the heart, leading to cardiac arrest and finally death.

Foxglove can cause irregular heart function and death. Signs of foxglove poisoning include stomach upset, small eye pupils, blurred vision, strong slow pulse, nausea, vomiting, dizziness, excessive urination, fatigue, muscle weakness and tremors, stupor, confusion, convulsions, abnormal heartbeats, and death. Long-term use of foxglove can lead to symptoms of toxicity, including visual halos, yellow-green vision, and stomach upset.
Deaths have occurred when foxglove was mistaken for comfrey.
Foxglove: “In 1775 an English doctor named William Withering (1741-1799) began studying the foxglove plant. He learned that an effective medicine for treating heart ailments could be made from drying leaves picked just before the plant blossomed and crushing them into a powder. Withering also discovered that this medicine, digitalis—one of a number of substances called found in the plant—could be poisonous if the patient was given too much. Withering was aware that digitalis was effective only in certain forms of dropsy (edema), but apparently did not associate this with the cardiac actions of the drug. Withering published his findings about digitalis in 1785, but in spite of his warnings about proper dosage, many doctors prescribed the medicine in doses that were too large and for sicknesses it could not cure.
The active principles of digitalis were not known to researchers until the mid-1800s, when two French scientists, Homolle Ouevenne and Theodore Ouevenne, found the substance digitalin in the foxglove plant. In 1875 Oscar Schmiedeberg (1838-1921) identified the potent chemical digitoxin in the plant, and in 1930 the English chemist Sydney Smith obtained the medicine used today, digoxin, from the wooly foxglove plant, Digitalis lanata.
Today doctors know that if too much digitalis enters the circulatory system the patient may experience nausea, vomiting, trouble with vision (seeing too much yellow or green), and a very slow and irregular heartbeat. A larger amount of digitalis can result in convulsions (severe seizures) and death. Even grazing animals that eat too much of the foxglove plant can become poisoned by its glycosides.”
Foxglove, any of about 20 species of herbaceous plants of the genus Digitalis (family Plantaginaceae), especially Digitalis purpurea, the common, or purple, foxglove, which is cultivated commercially as the source of the heart-stimulating drug digitalis.

Basic Information

Anatomy

The plants produce alternating, ovate to oblong leaves toward the lower part of the stem, which is capped by a tall, one-sided cluster of pendulous, bell-shaped flowers, each of which may be up to 6.5 cm (2.5 inches) long. The flowers may be purple, yellow, or white and are often marked with spots within.

Biological Cycle

Most species are biennials, meaning they flower during their second year and then die after seeding.

Alternative names:

Dead Man's Bells, Fairy Cap, Fairy Finger, Lady's Thimble, Lion's Mouth, Purple Foxglove, Scotch Mercury, Throatwort, Witch's Bells, Woolly Foxglove.

Scientific Name

Digitalis purpurea

Origin/Ancestry

Foxgloves are native to Europe, the Mediterranean region, and the Canary Islands.

Lifespan

Two years

Average Height

they typically grow to a height of 45 to 150 cm (18 to 60 inches).