(CBS/AP)-- A popular heart drug used to control abnormal heart rates may cause patients who take it to die earlier, according to a new study.
The study, which was published online in the European Heart Journal on Nov. 27, 2012, showed that patients who took digoxin who had atrial fibrillation (AF) -- a condition where the heart's upper chambers flutter erratically -- died in significant numbers while on the medication.
Digoxin is made from an extract from the foxglove plant used on patients who have AF and heart failure. Theoretically, it makes the heart beat stronger and more regularly. It is notoriously hard to use because there is a narrow dose range between where it is helpful and when it can cause harm. High doses have been seen to increase death in patients.
For the study, researchers looked at data from 4,060 AF patients who took digoxin before or during the 3.5 year study. The subjects had all enrolled in the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) to determine any affects digoxin had on increased death rates.
Digoxin was associated with a 41 percent increase in deaths from any cause, after controlling for other factors. Patients who took digoxin also had a 35 percent increase in deaths from cardiovascular causes, and a 61 percent increase in deaths from arrhythmias, or problems with heart rate.
"These results mean that among AF patients taking digoxin compared to those not on digoxin in the AFFIRM trial, within five years one additional patient out of six will die from any cause, one additional patient out of eight will die from cardiovascular causes, and one additional patient out of 16 will die from arrhythmias," Samy Claude Elayi, associate professor of medicine at the Gill Heart Institute, University of Kentucky, in Lexington, Ky., said in a press release.
Elayi added that the results show that widespread use of dioxin may be detrimental to patients who are suffering from AF. However, the findings do not show that the medication is bad for everyone he pointed out to Reuters.
"But in patients that have no heart failure and (have) atrial fibrillation, I think there is no reason to use this drug as a first line," Elayi said.
Dr. Ali Ahmed, who has studied digoxin at the University of Alabama at Birmingham, told Reuters that the study was flawed because it was looking for problems caused by digoxin and did not assign people blindly to the study. He said other "confounders" like other patient diseases may have caused the deaths.
"This should be taken with extreme caution, because of the potential for confounding and bias from a variety of sources," Ahmed, who wasn't involved in the new research, said.
Natasha Stewart, senior cardiac nurse at the British Heart Foundation (BHF), added to the BBC that while digoxin isn't the first medication of choice in the U.K., some patients are taking it -- and there are plenty of benefits for AF and heart failure patients.
"Before we jump to any conclusions about the dangers of the drug, we'd need to see further research into what might be causing these increased risks," she said. "Patients who are prescribed digoxin should not stop taking their meds without discussing their concerns with their doctor."