Foxglove

 

DIGITALIS PURPUREA

COMMON NAME : Foxglove


Poisonous plant no longer used by Herbalists


FAMILY  :        Scrophulariaceae  (Figwort family)


HABITAT / GROWING:

Biennial, occasionally perennial. Western European native. Many garden variants exist. Foxgloves growing in

the wild have the best medicinal properties.


PARTS USED :  Leaf.


TRADITIONAL & MODERN USE:

Traditionally used to treat dropsy. Welsh housewives used to make a black dye from its leaves with which they painted crossed lines on the stone floors of their cottages. This was probably done to keep witches away and may have derived from a superstition held in the Middle Ages that it was an anti-witch plant.


The common name may derive from the Anglo-Saxon “foxes-glew” or “fox music” after the shape of an ancient musical instrument. The name could also have come from “Folks glove”, the glove of the “Good Folk” or fairies. Digitalis came from the latin “digitabulum” a thimble.


It became important in medicine when Dr William Withering published his “account of the foxglove” in 1785. The whole field of digitalis therapy is still based on his work. Prior to this, foxglove had been used for a long time but to treat completely different conditions. It was listed as a drug to treat epilepsy, heal wounds and as an expectorant.


It acts as a cardio-active diuretic in conditions of oedema due to heart failure.  It may be used externally as a poultice to aid healing of wounds.


The medicinal action of digitalis only develops fully when heart disease is present. It has no appreciable effect on a normal heart except that higher doses will be toxic. The more severe the heart failure, the greater the dose of digitalis required and the more marked will be the effect. It was found that the accompanying principles provided in the whole plant also have a role to play. This role appears to be to improve absorption. Substances called “ballast” not so long ago, with efforts made to remove them, have now shown themselves to be useful and even desirable.


Digitalis increases the force of contraction of the heart (positively inotropic), slows down the heart rate (negatively chronotropic) and decreases conduction in the auriculoventricular bundle (negatively dromotropic). It also increases response to  stimulus (positively bathmotropic).


Digitalis is an excellent antidote for aconite poisoning, given as a hypodermic injection.Atropine is administered for digitalis poisoning.


CONSTITUENTS:

Foxglove contains several glycosides including digitoxin, gitoxin and gitaloxin, which act directly on heart muscle, increasing the output in patients with congestive heart failure.


Digitalis contains four important glucosides of which three are cardiac stimulants : digitoxin (the most powerful) , digitalin and digitalein. Digitonin is a cardiac depressant and may be responsible for the digestive disturbances. Foxglove also contains volatile oil, fatty acids, sugar, starch and gum.


Cardiac glycosides  have two components, a genin and a sugar. The action on the heart is due to the genin component. The problem with digitalis glycosides compared to other cardiac glycosides is that the full therapeutic dose is very close to that at which toxic effects develop.


Digitoxin is obtained from Digitalis purpurea, while digoxin is obtained from Digitalis lanata (Austrian or woolly foxglove) Digoxin is obtained from lanatoside C by fermentation. Digitalis lanata is now the most widely used species as it can be cultivated on a large scale. It also remains in the heart for a shorter time and so has less risk of accummulation.