Calcium channel blockers interfere with the movement of calcium ions across cardiac cell membranes. This action slows the conduction rate of electrical impulses through the heart muscle, which slows the heart rate. Patients take calcium channel blockers such as diltiazem and verapamil to control irregular heart rhythms such as atrial fibrillation and supraventricular tachycardia. Calcium channel blockers primarily affect the cardiovascular, central nervous and gastrointestinal systems.
Bradycardia
Because calcium channel blockers delay the rate of electrical impulse transmission through the heart muscle, the heart rate slows. Sometimes the heart rate gets too slow and a condition called bradycardia develops. Bradycardia can cause symptoms of dizziness, fatigue and shortness of breath. If the heart rate is too slow, extra irregular heartbeats may escape from the ventricle in an effort to speed up the heart rate. A slow heart rate and an irregular heart rate cause low blood pressure, too. The Nationals of Health reports that 15 percent of clinical trial participants taking the calcium channel blocker verapamil experience bradycardia and 5 percent of these people suffered a corresponding hypotension or low blood pressure.
Heart Block
“Pearson Nurse’s Drug Guide 2010” warn that heart block can occur while taking a calcium channel blocker. A heart block is the inability of the heart to regularly transmit the signal for the heart to beat from the top chambers to the lower chambers. A second-degree or a complete heart block may result. These two irregular heart rhythms require medical intervention. Stopping the calcium channel blocker may be all that is required. In extreme and rare cases, a pacemaker may be needed to support the heart rate and rhythm until the calcium channel blocker effect wears off.
Hypotension
Low blood pressure occurs frequently when patients take calcium channel blockers. Calcium channel blockers dilate and relax blood vessels and lower the resting blood pressure. This action makes calcium channel blockers good choices to treat vasospastic chest pain and high blood pressure; however, patients frequently experience orthostatic hypotension. Orthostatic hypotension is low blood pressure with position changes. Patients taking calcium channel blockers should get up and change positions slowly to allow the body to adjust to the change in blood pressure. With postural hypotension, the blood pressure can drop 20 or more millimeters of mercury when patients change from a sitting position to a standing position. Patients experience dizziness and feel faint.
Constipation
Constipation occurs in 7.3 percent of calcium channel blocker users, according to the NIH. Patients can treat this common side effect by eating a high fiber diet, maintaining an adequate fluid intake, reducing caffeine consumption and participating in regular exercise. Other gastrointestinal symptoms that may accompany constipation are nausea, indigestion and vomiting. If holistic measures do not alleviate constipation, patients may need to take stool softeners and should consult with a physician.
References
- National Institute of Health DailyMed Sheet: Verapamil
- “Pearson Nurse’s Drug Guide 2010”; Billie Ann Wilson, PhD., Margaret Shannon, PhD., Kelly Shields, PharmD.; 2010
