First identified in the late 1960s, calcium channel blockers (also called CCBs or calcium antagonists) are non-habit-forming medications that are used to relax the smooth muscles of the arteries and arterioles as well as the heart muscle, which reduces the workload on the heart and causes a drop in blood pressure.

Calcium is considered an excitatory element. In other words, when calcium flows into certain cells, such as smooth muscle cells located in arteries or muscle cells in the heart, it causes them to contract. In a normal heart, the regular heart rhythm is controlled by the flow of ions such as calcium and potassium into and out of muscle cells.

Calcium channel blockers fall into one of two categories. Some of them affect the contractile strength of the heart, while others are vasodilators that cause arteries to relax and widen. The choice of which calcium channel blocker to use depends on the condition being treated. By inhibiting calcium, physicians are able to reduce the contractile energy of arterial smooth muscle and heart muscle.  As a result, blood pressure is lowered and circulation is improved. Calcium channel blockers may be prescribed for people with high blood pressure (hypertension). They also reduce the workload of the heart, so they may be prescribed for hypertrophic cardiomyopathy.

Other conditions that may be treated by these medications include coronary artery disease, certain abnormal heart rhythms (arrhythmias) and history of a specific type of heart attack.

Side effects may include a brief headache that should fade over time. The medication can also cause low blood pressure (hypotension), dizziness, swelling (edema) in the lower legs, constipation, fatigue, stomach discomfort, heart failure and conduction defects.