A calcium channel blocker reduces the amount of calcium entering the cells of the heart and blood vessel walls, according to MayoClinic.com. A calcium channel blocker, also termed a calcium antagonist, relaxes and widens blood vessels of the heart within the arterial walls, promoting lowered blood pressure. Calcium channel blockers may also slow the heart rate, relieve chest pressure and control an irregular heartbeat.
Types
A calcium channel blocker has two available types: short-acting and long-acting. Short-acting calcium channel blockers work quickly; however, their effects only last a few hours. Long-acting calcium channel blockers slowly release their medication to provide a longer-lasting effect. Long-acting calcium channel blockers are more frequently used to treat high blood pressure, since they have been proven to reduce the risk of heart attack and stroke, while their short-acting counterparts have been associated with adverse cardiovascular outcomes, according to Leonard Lilly, M.D., author of "Pathophysiology of Heart Disease."
Examples of generic calcium channel blockers include amlodipine, diltiazem, felodipine, isradipine, nicardipine, nifedipine, nisoldipine and verapamil.
Mechanism
The slowed pace of calcium entering the heart muscle and vessel walls causes the heart vessels to relax, allowing blood to flow more easily through them. The heart's pumping strength also decreases. The combination of these two factors results in lowered blood pressure.
Typically, calcium channel blockers are not the first line of medication prescribed to lower blood pressure, since they're not as effective as diuretics, beta blocks and angiotensin-converting enzyme, or ACE, inhibitors, according to MayoClinic.com. However, calcium channel blockers may be used in combination with these other medications to further lower blood pressure, especially in extremely hypertensive individuals.
Adverse Effects
The Texas Heart Institute states that common side effects associated with calcium channel blockers include tiredness, heartburn, and swelling of the abdomen, ankles or feet. Less common side effects include a very fast or very slow heartbeat, wheezing, cough, shortness of breath, trouble swallowing, dizziness, upset stomach, constipation and numbness or tingling in the hands or feet. Rare side effects consist of headache, fainting, chest pain, yellowing of the skin, fever, rash, vivid dreams, and bleeding, swollen or tender gums.
Overdose
Calcium channel blocker overdose can be extremely dangerous and life-threatening. Survival depends on the amount of medication taken and how quickly the person receives medical treatment. MedlinePlus states that common symptoms of a calcium channel blocker overdose include confusion, dizziness, drowsiness, irregular heartbeat, slow heartbeat, nausea, slurred speech, shortness of breath and weakness.
MedlinePlus states that anyone suspicious of an overdose should call 9-1-1 or the National Poison Control Center at 1-800-222-1222. The Center is available 24 hours a day, seven days a week, offering free and confidential service.
References
- MayoClinic.com: High Blood Pressure (Hypertension)
- Texas Heart Institute: Calcium Channel Blockers
- MedlinePlus: Calcium Channel Blocker Overdose
- "Pathophysiology of Heart Disease;" Leonard Lilly; 2007.
