Calcium Channel Blockers

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.

As far as interactions go, verapamil should not be given to patients who are also taking digoxin, since this can increase the risk of heart block. Verapamil also increases the serum level of digoxin, which increases the risk of digoxin toxicity. Verapamil can also interact with beta blockers, which can cause bradycardia and suppress cardiac contractility. In addition, consumption of grapefruit juice can increase the serum level of calcium channel blockers, especially felodipine and nifedipine... and alcohol can intensify the hypotensive effects of calcium channel blockers.

Now, when caring for a patient who’s been prescribed a calcium channel blocker, begin by assessing for contraindications to calcium channel blocker therapy, and check their medication administration record for potential medication interactions. Then, perform a baseline assessment, with a focus on their blood pressure and heart rate; and check for the presence of peripheral edema. Review their laboratory test results including renal and liver function tests as well as the results of their ECG. While providing care, monitor your patient closely for side effects and evaluate the effectiveness of therapy.

Finally, when educating your patient about calcium channel blocker therapy, focus your teaching on safe self-administration. Be sure they understand why their medication is prescribed, and the recommended length of treatment. Instruct them to take their medication exactly as directed, and to not abruptly stop taking their medication. Teach them about any dietary modifications they should make, such as increasing fluids and fiber, limiting alcohol, and avoiding grapefruit juice. Review other common side effects they may experience, and ensure they understand when they should notify their health care provider.

Alright, as a quick recap.... Calcium channel blockers are used to treat hypertension, angina, and cardiac dysrhythmias. Commonly prescribed calcium channel blockers include nondihydropyridines, like verapamil and diltiazem; and dihydropyridines, like nifedipine and amlodipine. Calcium channel blockers work by preventing calcium from binding with receptors inside of cells, causing vasodilation, as well as slowing conduction through the atrioventricular node, and decreasing the force of the heart’s contraction. Side effects of calcium channel blockers include headache, flushing, dizziness, peripheral edema, hypotension, and bradycardia. Nursing considerations include establishing a baseline assessment, monitoring for side effects, evaluating the effectiveness of therapy, and providing teaching for safe self-administration.