Medicinal Plants in Cardiology: Foxglove
A beautiful medicine and a deadly poison, digitalis has played a special role in the treatment of heart failure for centuries.
For centuries, people have used the foxglove plant (primarily the species Digitalis purpurea in the Plantaginaceae plant family) as a diuretic and heart remedy, possibly dating back to the Roman era. During the Middle Ages, folk healers used foxglove extracts to treat swelling (though overdoses led to serious effects). Modern understanding of digitalis largely began with William Withering in the eighteenth century. A gifted physician and botanist, Withering carefully tracked how foxglove relieved symptoms in people with congestive heart failure (then called “dropsy”). Congestive heart failure is a condition in which the heart is unable to pump enough blood to the rest of the body. Symptoms can include shortness of breath, cough, fatigue, weakness, irregular or rapid pulse, loss of appetite, swelling of the feet, ankles, and abdomen.
While Withering was certainly not the first to learn of the foxglove plant for this purpose, he was the first to broadly publish its effects. Much of what he learned was observed in the clinical practices of a healer he mentioned in his writings simply as “an old woman from Shropshire.” He wrote about these observations in 1785, noting that some patients benefited greatly while others did not, and he also described the plant’s potential toxic effects.
At a time when bloodletting was still standard, Withering’s careful recording of patient outcomes was revolutionary. His publication, An Account of the Foxglove and Some of its Medical Uses, helped launch evidence-based medicine by showing the importance of consistent preparation methods, detailed observation, and balanced dosing. Withering recognized that different patients respond to treatments in varying ways—something researchers today still account for when developing new drugs. His detailed approach to clinical research and his emphasis on standardized plant-derived medications marked a turning point in medical history.
How Does Foxglove Work?
The active components of the foxglove plant are the cardiac glycosides digoxin and digitoxin. While the mechanism of action is not fully understood, what is known is that these cardiac glycosides inhibit the ATPase activity of a complex of transmembrane proteins that form the sodium–potassium adenosine triphosphatase (Na+/K+-ATPase) pump. Inhibition of this pump causes a rise in intracellular sodium and calcium, which in turn results in increased force of myocardial muscle contractions. In other words, a chemical shift in the heart tissue occurs, yielding a stronger contraction of the heart, more effectively moving blood through the body.
The challenge with these molecules is that the therapeutic dose is very close to the toxic dose and thus must be carefully monitored. Death from foxglove poisoning occurs from ventricular fibrillation—uncontrollable quivering of the lower chambers of the heart instead of pumping the blood effectively.
Though commonly used as a ornamental plant due to its beauty, take caution to ensure that young children and pets don’t accidentally ingest this plant!
Use in Cardiology Today
Today, digitalis (often called digoxin) is used in modern medicine primarily to help control symptoms in people with congestive heart failure and sometimes atrial fibrillation. Although it increases the heart’s pumping strength and can lower heart rate at rest, it usually does not significantly lower mortality rates in heart failure. However, it can reduce hospitalizations and slow disease progression when used alongside standard treatments like ACE inhibitors, beta blockers, and other medications. Because maintaining a safe digoxin level is crucial, doctors often use the lowest effective dose to avoid toxicity. Patients taking certain drugs, such as amiodarone or verapamil, are at higher risk for digoxin toxicity if doses are not adjusted. Careful monitoring and good patient compliance are essential to ensure safety and effectiveness.
The Takeaway
Despite some controversy, many experts believe digitalis still has a place in modern congestive heart failure management, especially for symptom control.
Want to learn more? I found this 2018 review paper on the clinical use of digitalis to be particularly informative. If you or a loved one have congestive heart failure, seek the medical care of a cardiologist.
Yours in health, Dr. Quave
Cassandra L. Quave, Ph.D. is a Guggenheim Fellow, CNN Champion for Change, Fellow of the National Academy of Inventors, recipient of The National Academies Award for Excellence in Science Communication, and award-winning author of The Plant Hunter. Her day job is as professor and herbarium director at Emory University School of Medicine, where she leads a group of research scientists studying medicinal plants to find new life-saving drugs from nature. She hosts the Foodie Pharmacology podcast and writes the Nature’s Pharmacy newsletter to share the science behind natural medicines. To support her effort, consider a paid or founding subscription to Nature’s Pharmacy or donation to her lab research.
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