NCLEX Review Guide: Calcium Channel Blockers

How Calcium Channel Blockers Work

• Calcium channel blockers (CCBs) prevent calcium from entering cells through voltage-gated calcium channels, resulting in vasodilation and decreased cardiac contractility.
• Primary effects include reduced peripheral vascular resistance, decreased heart rate, and lowered blood pressure.

Primary Therapeutic Uses

• Hypertension management - First-line therapy, especially effective in elderly and African American patients.
• Angina prevention - Reduces cardiac workload and improves coronary blood flow through vasodilation.
• Arrhythmia control - Verapamil and diltiazem slow AV conduction for supraventricular tachycardia.

Critical Nursing Assessments

1. Monitor blood pressure and heart rate before each dose - hold if systolic BP <90 mmHg or HR <60 bpm for non-dihydropyridines.
2. Assess for peripheral edema, especially ankle swelling with dihydropyridines like amlodipine.
3. Monitor for signs of heart failure - dyspnea, weight gain, jugular vein distention.
4. Evaluate liver function tests as CCBs are hepatically metabolized.

Common Adverse Effects

• Peripheral edema occurs in 25-30% of patients taking dihydropyridines due to arterial vasodilation without venous dilation.
• Hypotension and dizziness especially during initial therapy or dose increases - teach patients to rise slowly.
• Constipation is most common with verapamil due to decreased GI smooth muscle contractility.

Critical Drug Interactions

• Grapefruit juice inhibits CYP3A4 and can significantly increase CCB levels, leading to dangerous hypotension.
• Beta-blockers with verapamil or diltiazem can cause severe bradycardia and heart block - avoid combination.
• Digoxin levels increase when combined with verapamil due to decreased renal clearance.