Side Effects of Hypertension Drugs May Increase Breast Cancer Risk: Study

Calcium blocker hypertension drugs, which includes Norvasc, Cardizem, Cardene, Procardia and Sular, could increase the risk of breast cancer, according to the findings of new research.  

In a study published this week in the online edition of the medical journal JAMA Internal Medicine, researchers from the Fred Hutchinson Cancer Research Center in Seattle, Washington found that this class of hypertension drug was associated with higher risks of ductal breast cancer and lobular breast cancer.

The study looked at data on 2,763 women in the Seattle-Puget Sound Metropolitan area between the ages of 55 and 74. Of the subjects, 880 of them had invasive ductal breast cancer, 1,027 had invasive lobular cancer and 856 had no cancer. Researchers looked at their use of hypertension drugs.

According to the findings, women who took calcium channel blockers were 2.5 times more likely to have breast cancer, compared to women who took different hypertension drugs or no hypertension drugs at all. The risks did not appear to vary between different calcium channel blockers.

The findings do not establish a causal link between the hypertension drugs and breast cancer, the researchers note. In addition, some previous studies have provided conflicting findings.

“This is the first study to observe that long-term current use of calcium-channel blockers in particular are associated with breast cancer risk,” the researchers said in their conclusions. “Additional research is needed to confirm this finding and to evaluate potential underlying biological mechanisms.

How the drugs could cause breast cancer or increase the risk is unknown. Calcium channel blockers stop calcium from entering the cells of the heart and blood vessels, this helps lower blood pressure. They relax and widen blood vessels and can also lower the heart rate, and are sometimes used to treat chest pain and irregular heart rhythms.