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Digitalis purpurea


By Eric Van De Graaff, MD March 22, 2010 Posted in: Heart Health

Springtime’s finally here.  Around my house this is the time of year when my seven-year-old daughter and I call upon our years of collective gardening experience and expertise to create chaos in our vegetable and flowerbeds.  Every year I seem to find new ways to take what should be a fairly simple and straightforward practice—till soil, plant seeds, add water—and create nothing more than a jungle of poorly blooming stalks, barren vegetable plants, and an unusually hardy crop of weeds.  Even the easy ones, such as tomatoes and cucumbers, end up as nothing more than a puzzle of fruitless vines.  This is Nebraska, for goodness sake, and I can’t even grow corn.

One thing we’re pretty good at, though, is foxglove.  This beautiful perennial is a favorite of my daughter’s and we plant it in front of our house year after year.  The pink, tubular blossoms look as if God had designed them with fairy tale illustrators in mind and could easily grace the pages of any work featuring brownies and sprites.  For me, the allure of this plant has more to do with chemistry than aesthetics.

The scientific name for the most common form of foxglove is Digitalis purpurea (the “digit” part of Digitalis connotes the human fingertip over which the delicate blossoms can easily fit) and it is from an extract of this genus that we acquire the commonly used cardiac drug digitalis, currently available as digoxin (Lanoxin, Digitek, Lanoxicaps).

Digitalis is a cardiac glycoside, a chemical that affects movement of sodium and potassium in and out of heart muscle cells and thereby indirectly increases the concentration of calcium inside the cell.  This leads to a couple of therapeutic effects that are quite favorable for patients suffering from various heart ailments.  Elevated calcium levels promote a stronger force of ventricular contraction—a particularly useful byproduct for patients with weak hearts and congestive heart failure.  It also leads to a slowing of electrical conduction in certain areas of the heart’s wiring.  In patients with atrial fibrillation or other rhythm disorders that lead to rapid heart rates, digitalis can slow the pulse rate to a more moderate pace.

The therapeutic effect of foxglove extract was first formally described by Dr. William Withering in 1785.  Ten years earlier, Withering, who plied his trade among the poorer and more destitute patients of England, was introduced to an uncommon folk remedy for dropsy (congestive heart failure) that “had long been kept a secret by an old woman in Shropshire who had sometimes made cures after more regular practitioners had failed.”

His 1785 paper on the use of foxglove in the treatment of dropsy had limited impact on local medical practices at the time but years later makes for fascinating reading.  In it he confesses to the use of a decidedly unscientific method for testing the dose of the drug needed to achieve the desired action in his patients, all the while avoiding the nasty, somewhat toxic adverse effects.  You see, digitalis is also a potent poison when used in excess (in fact, one of the most notorious serial killers of the last twenty years was a nurse who used digoxin as his weapon of choice to claim the lives of at least 45 victims).

Dr. Withering would blend the leaves and petals of the plant and distill them into a soupy mix that he would feed to his patients.  Over time (and with several notable failures) the good doctor learned to give just enough to bring on nausea, weakness and a peculiar change in vision (the colorful world starts to fade to shades of yellow).  The goal of therapy was to saturate the patient to within a sip or two of fatal overdose.  We now recognize these symptoms as the final stages of severe digitalis toxicity and try to never let our patients get even close to Withering’s benchmark.  Thanks to precisely formulated dosing and the ability to test blood levels of the chemical, the problem of digitalis toxicity has become quite rare.

Once Dr. Withering’s cure for dropsy spread to the wealthy upper crust of London it became an smash hit in the world of botanical pharmacopoeia, even inspiring a ode to the chemical by the grandfather of Charles Darwin.  The elder Erasmus Darwin was a physician and contemporary of Dr. Withering and jointly consulted on numerous dropsy patients:

Pale Dropsy rears his bloated form, and pants;
"Quench me, ye cool pellucid rills!" he cries,
Wets his parch'd tongue, and rolls his hollow eyes.
Divine HYGEIA, from the bending sky
Descending, listens to his piercing cry;
Assumes bright DIGITALIS' dress and air,
Her ruby cheek, white neck, and raven hair.

Erasmus Darwin

Historians have argued whether Mr. Darwin was himself dipping into the foxglove stew or if he was just plain crazy as he penned some of the most regrettable stanzas in the history of botanical poetry.

I, on the other hand, have a deep appreciation for the beauty of foxglove on both an aesthetic and chemical plane.  Thus, in honor of this plant and its place in history, as well as a nod to Drs. Withering and Darwin, I’ll end this week’s post by offering the literary world the second great piece of digitalis poetry:

Ode to Foxglove
by Eric Van De Graaff

Now my heart is weaker,
Breathing getting bleaker,
Swelling in my hallus--
Need some digitalis.
Seed a planter box of
Tasty, juicy foxglove.
Water, weed and tend,
Leaves and blossoms blend.
With one gulp I swallow
Hope effects will follow.
Dose it right it’s great,
Too much seals your fate.
For many sick and ill
A truly useful pill;
But if you’re dumb like me
And brew a foxglove tea
The only thing you’ll see
Is it’s toxicity.
Dizzy, weak and mellow,
World is turning yellow,
Heartbeat now so slow,
To the ground I go.
With final words I jot
A lone, last dying thought:
Why ever did I raise these?
Shoulda stuck with daisies.

Eric Van De Graaff, MD
Eric Van De Graaff, MD

Eric Van De Graaff, MD is a Heart & Vascular Specialist at CHI Health Clinic.

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