Calcium channel blockers are medicines used to lower blood pressure. They stop calcium from entering the cells of the heart and arteries. Calcium makes the heart and arteries squeeze more strongly. By blocking calcium, calcium channel blockers allow blood vessels to relax and open.

Some calcium channel blockers also can slow the heart rate. This also can lower blood pressure. The medicines may be given to relieve chest pain, called angina. They also can help control an irregular heartbeat.

Calcium channel blockers are sometimes called calcium antagonists.

Examples of calcium channel blockers

Calcium channel blockers are available in short-acting and long-acting forms. Short-acting medicines work quickly. But their effects last only a few hours. Long-acting medicines are slowly released. So they last longer. Which one is best for you depends on your health and the condition being treated.

Examples of calcium channel blockers include:

• Amlodipine (Norvasc).
• Diltiazem (Cardizem, Tiazac, others).
• Felodipine.
• Isradipine.
• Nicardipine.
• Nifedipine (Procardia).
• Nisoldipine (Sular).
• Verapamil (Verelan).

Sometimes, a calcium channel blocker may be used with other high blood pressure medicines.

When calcium channel blockers are used

Calcium channel blockers are used to treat high blood pressure. But they also may be used to prevent, treat or improve symptoms of some conditions. Examples are:

• Coronary artery disease.
• Chest pain, called angina.
• Irregular heartbeats, also called arrhythmias.
• Blood vessel conditions, such as Raynaud’s disease.

For Black people, calcium channel blockers might work better than other blood pressure medicines. Other blood pressure medicines include beta blockers, angiotensin-converting enzyme inhibitors, also called ACE inhibitors, and angiotensin 2 receptor blockers.

Side effects

Possible side effects of calcium channel blockers are:

• Constipation.
• Dizziness.
• Fast heartbeat you can feel.
• Extreme tiredness.
• Flushing.
• Headache.
• Nausea.
• Swelling in the feet and lower legs.

Do not eat grapefruit or grapefruit products while taking the calcium channel blockers diltiazem and verapamil. Grapefruit juice interacts with these medicines and can affect heart rate and blood pressure. This can cause symptoms such as headaches and dizziness.

Talk with your healthcare team if you have any questions about the medicines you take.