A drug known as amiodarone, used to treat heartbeat irregularities, could raise a person’s cancer risk, according to new research published in the journal Cancer.

The study reveals that the risk, which the investigators described as “borderline significantly increased”, is more prevalent in men and people who take greater doses of amiodarone.

Amiodarone was approved for use in 1985 for the treatment of arrhythmias, or irregular heartbeats. The medication is fat-soluble and breaks down slowly, leaving large amounts to build up in soft tissues after a long-term treatment period.

Earlier studies have indicated that amiodarone may elevate the risk of certain cancers, however, no large-scale study has investigated this issue.

Amiodarone is generally prescribed to avoid life-threatening arrhythmias, like ventricular tachycardia or ventricular fibrillation – both of which can cause cardiac arrest.

Ventricular tachycardia is a condition where the upper chambers of the heart beat very fast, and when those chambers don’t beat in the right sequence (ventricular fibrillation). These conditions stop blood from being pumped properly and can make the heart stop beating altogether.

The current study was led by Vincent Yi-Fong Su, MD, of the Taipei Veterans General Hospital in Taiwan, and his colleagues who examined 6,418 people who took the drug and followed them for at least 2.57 years. Of the participants, 280 developed cancer.

The researchers obtained data from the Taiwan National Health Insurance Research database. Patients involved were treated with amiodarone between 1997 and 2008.

Male patients as well as those who received a high daily dose of amiodarone within the first year had an elevated risk of developing cancer.

Patients with both factors were more likely to develop cancer than those without either factor. After accounting for illnesses, sex, and age, researchers found that subjects taking a high dose of amiodarone had close to twice the risk of developing cancer, compared with those taking a low dose of the drug.

The cancers shown to be associated with amiodarone were:

  • lung
  • ovaries
  • prostate
  • liver
  • digestive system
  • colon

Dr. Vincent Yi-Fong Su concluded:

“When prescribing amiodarone, doctors need to keep in mind that this medication may increase cancer risk. We suggest that cancer events should be routinely reported in future amiodarone trials, and further observational research is necessary.”

In 2011, Baxter International Inc. introduced the first ready-to-use IV amiodarone.

Written by Kelly Fitzgerald