Digitalis, the dried leaf of the foxglove (digitalis purpurea), is a cardiotonic drug, used to treat heart arrhythmia. Administered in its refined forms of Digoxin and Digitoxin, digitalis works strengthens the force of the heartbeat by increasing the amount of calcium in the heart's cells. Digitalis binds to sodium and potassium receptors, which control the amount of calcium in the heart muscle. As calcium builds up in the cells, it causes a stronger heartbeat. Irregular heart rhythms are controlled by slowing the signals that start in the sinoatrial (SA) node, in turn reducing the number of signals that travel through the atrioventricular, resulting in fewer arrhythmias. Blood circulation is improved and swelling of the extremities is reduced.
A therapeutic regimen including digitalis requires diligent monitoring of the patient; the therapeutic dosage of digitalis is only 1/3 that of a toxic dose. Age, kidney disease, metabolic disorders and interaction with other drugs can all lead to digitalis toxicity. Digitalis is the fourth most frequently prescribed drug in the United States. As with all medicines, keep out of the reach of children.
Digitalis has been used to treat heart conditions since 1785 when it was isolated by Scottish doctor William Withering, in Shropshire, England although it had been used in folk medicines for much longer. Digitalis extract was used as a poison for the medieval "trial by ordeal". It was also used externally to promote the healing of wounds. There are also reports of digitalis extract finding some use in the treatment of dropsy.
In 1775, a patient with a very bad heart condition called upon Dr. Withering, who unfortunately could offer no effective treatment for him. Instead of simply accepting the dismal prognosis, the patient went to a local gypsy, who gave him a secret herbal remedy. The patient promptly got much better!
This news excited the good doctor who proceeded to track down the gypsy throughout Shropshire. When he eventually he found her he insisted on learning the ingredients of effective remedy. Only after hard bargaining, did the gypsy finally reveal her secret: the active ingredient was the purple foxglove. Trying out various formulas of foxglove on 163 patients, Withering eventually found his best results from the dried, powdered leaf and he introduced its use officially in 1785.
When Dr. Withering died in 1799, his friends carved a bunch of foxgloves on his memorial.
When my parents were young, children at the Oregon coast earned money collecting foxgloves, which grew wild along all the country roads, and selling them to pharmaceutical companies. Foxgloves are now grown commercially for the extraction of digitalis.
Sources: The School of Chemistry at the University of Bristol, "Molecule of the Month" http://www.bris.ac.uk/Depts/Chemistry/MOTM/
Texas Heart Institute http://www.tmc.edu/thi/