A drug called amiodarone that's widely used to treat heartbeat irregularities
might raise a patient's risk of cancer, Taiwanese researchers report.
The risk, which the researchers termed "borderline significantly increased",
is more pronounced in men and patients who take high doses of the drug,
according to the study, which was published online.
"When prescribing amiodarone, doctors need to keep in mind that this
medication may increase cancer risk," said lead author Dr Vincent Yi-Fong Su,
from the Taipei Veterans General Hospital. "We suggest that cancer events should
be routinely reported in future amiodarone trials, and further observational
research is necessary."
Patients taking the drug, however, shouldn't fear they'll get cancer, one
"Amiodarone is among the most effective antiarrhythmic medications
available," said Dr Gregg Fonarow, a spokesman for the American Heart
Association and professor of cardiology at the University of California, Los
Angeles. "Well-controlled clinical trials have not demonstrated a significant
increase in cancer with use of this medication."
The current study, called an observational study, doesn't prove that
amiodarone causes cancer, only that an association was found between people
taking the drug and cancer.
Many risk factors for heart disease and arrhythmia are also risk factors for
cancer, Fonarow said. The findings of this study comparing those treated with
amiodarone to the general population are most likely explained by selection of
patients and other factors that weren't taken into account, he said.
"These findings should not be a concern to patients taking amiodarone,"
High doses, higher cancer risk
Amiodarone (sold as Cordarone and Pacerone) is commonly prescribed to prevent
life-threatening arrhythmias, such as ventricular tachycardia or ventricular
fibrillation, both of which can lead to cardiac arrest.
Ventricular tachycardia is a very rapid beating of the upper chambers of the
heart. When these chambers don't beat in the correct order, the condition is
called ventricular fibrillation. These problems prevent blood from being pumped
properly and can cause the heart to stop beating altogether.
Amiodarone breaks down slowly, so large amounts can remain in soft tissues
when the drug is taken for a long time. This might explain its association with
cancer, the researchers said. Earlier studies have shown an association between
amiodarone and cancer risk, but this is the largest study to date to show a
link, they noted.
For the study, Su's team followed more than 6 400 patients taking amiodarone
for almost three years. Among these patients, 280 developed cancer.
Men taking high doses of the drug had a 46% higher chance of developing
cancer than those who were neither male nor taking large doses. Anyone taking
high doses had nearly twice the risk of cancer compared with people taking low
doses, the researchers found.
Cancers of the digestive system, lung, liver, colon, ovaries and prostate
were among the cancers associated with amiodarone, the researchers said.
For more information on amiodarone, visit the US
National Library of Medicine.
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