NEW YORK (Reuters Health) - Use of the heart drug digoxin appears to increase the risk of breast cancer in postmenopausal women, according to the results of a study published in Breast Cancer Research.

Digoxin helps the heart pump stronger and is used to treat heart failure. The drug's name comes from the plant from which it is derived, Foxglove or Digitalis purpurea.

Dr. Thomas P. Ahern of Boston University and colleagues there and at Aarhus University Hospital in Denmark identified 5,565 postmenopausal women diagnosed with breast cancer between 1991 and 2007, and matched them with 55,650 healthy comparison subjects.

The researchers estimated the risk of breast cancer with digoxin use after accounting for age, county of residence, use of anticoagulants, nonsteroidal anti-inflammatory agents (NSAIDs), aspirin, and hormone replacement therapy.

Ahern's team identified a history of digoxin use of at least one year's duration in 324 breast cancer patients (5.8 percent) and 2,546 healthy subjects (4.6 percent). Although this difference may seem small, it suggests that digoxin use increases the odds of breast cancer by 30 percent or more depending on the duration of use.

While a number of lab studies have suggested that drugs related to digoxin may reduce the risk of breast cancer, the current findings suggest that digoxin itself may have the opposite effect, Ahern and associates conclude.

SOURCE: Breast Cancer Research, online December 3, 2008.

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