Calcium Channel Blocker Therapy

Calcium channel blockers are a class of medications used to treat cardiac conditions, such as hypertension, angina, and arrhythmias. Calcium channel blockers are divided into two groups based on their chemical structure: nondihydropyridines, like verapamil and diltiazem; and dihydropyridines, like nifedipine and amlodipine.

Now, calcium is essential for the normal function of vascular smooth muscle, as well as the contraction of heart muscle, and electrical conduction through the heart. Calcium channel blockers work by preventing calcium from entering cells and binding with receptors. This causes vasodilation of the coronary arteries, which increases the blood flow and oxygen supply to the heart.

Vasodilation also occurs in arteries throughout the body, reducing peripheral vesicular resistance which decreases the heart’s workload and oxygen consumption. Blocking calcium also decreases the heart muscle’s force of contraction and it slows conduction through the atrioventricular node which slows the heart rate and helps treat cardiac arrhythmias.

So, the side effects of calcium channel blockers are mostly due to vasodilation, and can include headache, flushing, dizziness, peripheral edema, and hypotension. Bradycardia is also a common side effect due to the decreased velocity of conduction through the heart. There are also some medication specific side effects to be aware of. Verapamil and diltiazem can cause constipation and heart block; whereas amlodipine can lead to facial edema, and nifedipine is associated with reflex tachycardia, meaning the heart rate rises in response to vasodilation.

As far as contraindications go, calcium channel blockers should not be used in patients with hypotension, acute myocardial infarction, second- and third-degree atrioventricular heart block, or sick sinus syndrome, unless the patient has a pacemaker. Also, verapamil and diltiazem should be used with caution in patients with liver impairment. Lastly, IV verapamil is considered a high alert medication, meaning there’s an increased risk of patient harm when the medication is used in error.