FOXGLOVE – Digitalis purpurae
This plant is so magnificent both in it’s sheer beauty and medicinal potency that it has to have tribute paid to it even though it is no longer used by herbalists.
There are some lovely folklore associations with the plants name. Originally ‘folks-glove’ was linked to the gloves of the good folk or fairies whose favourite haunts were supposed to be in the deep hollows and woody dells where the Foxglove delights to grow. The mottlings of the Foxglove blossoms like the spots on butterflies wings and tails of peacocks were said to mark where the elves had placed their fingers. One legend ran that the markings of the flowers were a warning sign of the baneful juices secreted by the plant, which in Irish legend gave it the name, ‘Dead man’s thimbles’. And on it goes!
It is famously used by the medical profession for the treatment of heart failure as a cardiac stimulant and for heart arrythmias most notably, atrial fibrillation that often accompanies heart failure. It contains Glycosides such as Digitoxin & Digoxin that are extracted from the leaves of the plant in the second year of growth typically.
The mode of action is well understood; it inhibits sodium-potassium ATPase which ultimately increases the contractility of the heart muscle (positive inotropic), leading to increased stroke volume / output.
The drug has a very narrow therapeutic index which means that the therapeutic dose is very close to the toxic dose! It is an extremely toxic plant. Hence it has fallen out of use by herbalists for this reason. Even today it’s safety is questioned.
It was first discovered in 1785 by a Shropshire herbalist Dr. William Withering who wrote, ‘Account of the Foxglove’. This gave details of up to 200 cases in which it was used with success to treat mostly ‘dropsical’ conditions (fluid on the chest secondary to heart failure). It was thus brought to the attention of the medical profession and the rest is history!
Signs of poisoning are; an irregular pulse, low blood pressure, stomach irritation, severe headache, delerium, hallucinations and even seeing all objects as blue! It can lead to death by ultimately stopping the heart, hence it has earned names such as Dead man’s bells and Witch’s gloves.