Pathophysiology
Clinical meaning
Calcium channel blockers (CCBs) inhibit L-type voltage-gated calcium channels but differ critically in tissue selectivity. Dihydropyridines (DHP: amlodipine, nifedipine, felodipine) are vascular-selective, primarily relaxing arteriolar smooth muscle with minimal cardiac effects — they reduce systemic vascular resistance and are first-line for hypertension and vasospastic angina. Non-dihydropyridines (non-DHP: verapamil, diltiazem) have greater cardiac selectivity, slowing SA node automaticity, AV node conduction, and reducing myocardial contractility — making them useful for rate control in atrial fibrillation/flutter and SVT, as well as angina. The NP must apply prescribing logic: never combine non-DHP CCBs with beta-blockers (additive negative chronotropic and inotropic effects risk severe bradycardia, heart block, or cardiogenic shock), avoid non-DHP CCBs in HFrEF (negative inotropy worsens pump failure), and counsel patients to avoid grapefruit juice (CYP3A4 inhibition increases CCB levels).