Some evidence suggests calcium-channel blockers have an association with breast cancer and kidney problems.
Calcium-channel blockers can help lower your blood pressure.
Calcium-channel blockers, or CCBs, are often prescribed when other medications to treat high blood pressure aren’t working well. Commonly prescribed CCBs include amlodipine (Norvasc) and diltiazem (Cartia XT). Some CCBs are also used to treat chest pain (angina) and irregular heartbeats. “Agents such as amlodipine are very effective for high blood pressure, with relatively infrequent side effects. This makes them popular,” says Dr. Deepak Bhatt, a Harvard Medical School professor and editor in chief of the Harvard Heart Letter.
How they work
One of the properties of CCBs is that they relax the walls of your arteries, which helps to widen the arteries and allow more blood flow to the heart. As a result, your heart doesn’t have to work as hard, and your blood pressure goes down. CCBs are helpful when another type of high blood pressure drug called a beta blocker is unsuccessful, and they are more effective than beta blockers for preventing angina resulting from coronary spasm.
First-generation calcium-channel blockers were short-acting; some studies suggested they might be hazardous in certain people with heart disease. The newer, long-acting CCBs appear safe and effective in controlling high blood pressure. Side effects include diarrhea, nausea, and fatigue.
However, some recent evidence suggests other potential risks of CCBs. A study in the Dec. 18, 2013, Journal of the American Medical Association found that taking CCBs at the same time as the antibiotic clarithromycin (Biaxin) was associated with a small risk of kidney injury. A study published online Aug. 5, 2013, in JAMA Internal Medicine found that women who took CCBs for 10 years or more had more than double the odds of getting breast cancer.
What you should do
Dr. Bhatt says the benefits of lowering high blood pressure likely outweigh the potential risks of CCBs. While both studies found an association between CCBs and potential risks, they did not find that CCBs directly caused kidney trouble or breast cancer. “These sorts of observational studies are not the gold standard of clinical research. Sometimes, they can pick up signals of harm—such as cancer—that end up being real, though most of the time such studies cannot be confirmed.” As for the possible interaction between CCBs and antibiotics, he says, “it is biologically plausible, but the more important message is to avoid unnecessary use of antibiotics in the first place.” Bottom line: talk to your doctor about CCBs.