Calcium channel blockers

What does this medication do?
Calcium channel blockers, sometimes called calcium channel antagonists, are used to control high blood pressure (hypertension), chest pain (angina) caused by coronary artery disease and irregular heartbeats (arrhythmia). Calcium channel blockers are often taken in combination with beta-blockers or diuretics to help reduce blood pressure.

How does it work?
Calcium channel blockers are vasodilators, which means they widen (dilate) your blood vessels, letting blood flow through more easily. By relaxing your blood vessels, your blood pressure drops and your heart doesn't have to work as hard. Some calcium channel blockers also slow the heart.

How should I take it?
There are many different kinds of calcium channel blockers, so how much you need depends on what type you are taking. Talk to your doctor or pharmacist about how and when to take this medicine. If you are taking an "extended-release" calcium channel blocker, do not chew, cut or crush the pills.

What should I avoid while taking this medicine?
Check with your doctor or pharmacist about consuming grapefruit or grapefruit juice (fresh or frozen) because they may increase the effect of a certain class of calcium channel blocker and may cause your blood pressure to drop too much. A component in grapefruit juice appears to interfere with your body's ability to eliminate this medication. You should also avoid smoking while you are taking calcium channel blockers because it may cause a rapid heartbeat (tachycardia). Speak to your doctor or pharmacist about any other information you may need to know about your medications.

Visit Health Canada to learn more about The Effects of Grapefruit and its Juice on Certain Drugs.

What if I am taking other medicines?
Calcium channel blockers can interact with other medications, so be sure to tell your doctor about any other medication including prescription, non-prescription, over-the-counter or natural health products (vitamins and minerals, herbal remedies, homeopathic medicines, traditional medicines such as traditional Chinese medicines, probiotics and other products such as amino acids and essential fatty acids). Some medications that can cause an interaction with calcium channel blockers include ACE inhibitors, antiarrhythmics, digitalis, corticosteroids, large doses of calcium or vitamin D supplements.

What else should I tell my doctor?
Always check with your doctor or pharmacist before taking other medications on a regular basis. It is not safe to stop taking a calcium channel blocker without consulting your doctor.

What are some common side effects?
Calcium channel blockers have relatively few side effects, and these are rarely serious although they may be irritating. Among the most common are fatigue, dizziness/lightheadedness, heartburn and swelling of the ankles or feet. Tell your doctor if you have any of these side effects. Do not stop taking your medications without speaking to your doctor first.

Combination treatments
Most people with high blood pressure need two or more medications to lower their blood pressure. In many cases, two medications can be taken as a single tablet.

Lifestyle changes
Eating a healthy diet that is lower in fat, especially saturated and trans fats, being smoke free, limiting alcohol use, being physically active and reducing stress are also important to lowering the risk of heart disease. Talk to your health-care practitioner about how you can achieve these lifestyle changes.

For more information
Health Canada provides health and medical information to help Canadians maintain and improve their health. Learn more about Safe Use of MedicinesSafety and Effectiveness of Generic Drugs and Buying Drugs over the Internet.

Drug Product Database provides information about drugs approved for use in Canada.

MedEffect Canada provides safety alerts, public health advisories, warnings and recalls.

Your ministry of health also provides useful health resources in your province or territory. For example, Ontario has a MedsCheck program providing free pharmacist consultations on safety use of drugs. British Columbia has a Senior Healthcare webpage providing information about important health programs.  

Last modified: July 2011
Last reviewed: July 2011