In An Account of the Foxglove and Some of its Medical Uses, published in 1785, Sir William Withering cautioned readers that foxglove was not a perfect drug. “Time will fix the real value upon this discovery,” he wrote.

Foxglove, a genus of flowering plants, contains cardiac glycosides, which can be used to treat heart failure and atrial fibrillation — a rapid and irregular heart rhythm. Now, more than 200 years later, researchers at the School of Medicine have validated Withering’s warning with the discovery that patients with atrial fibrillation who are treated with digoxin, a glycoside commonly extracted from woolly foxglove, are more likely to die than similar patients who received different treatments.

“The take-home point is to question whether people should really be on this drug,” said the study’s lead author, Mintu Turakhia, MD, assistant professor of cardiology at Stanford and director of cardiac electrophysiology at the Veterans Affairs Palo Alto Health Care System. “These data challenge the current guidelines.”

The study was published online Aug. 11 in the Journal of the American College of Cardiology, and will appear in the Aug. 19 print issue of the journal.

Turakhia and his team analyzed records from 122,465 patients who received a new diagnosis of atrial fibrillation from the U.S. Department of Veterans Affairs health-care system between 2003 and 2008. Doctors prescribed digoxin to 23 percent of the patients, and 70 percent of those patients were still on the drug one year later. Patients treated with digoxin were 1.2 times more likely to die than comparable patients prescribed other therapies. Patients receiving digoxin were more likely to die regardless of age; use of other drugs such as beta-blockers, amiodarone or warfarin; or the presence of other factors such as kidney disease, heart attack or heart failure, the study found.