Dihydropyridine CCBs

A calcium channel blocker that drops blood pressure without slowing the heart — until reflex tachycardia kicks in and mimics the problem you're trying to prevent.

Dihydropyridine CCBs — amlodipine and nifedipine — selectively block L-type calcium channels in vascular smooth muscle with minimal effect on cardiac conduction tissue. This vasoselectivity is what separates them from verapamil and diltiazem. By preventing calcium entry into arterial smooth muscle cells, they cause potent peripheral vasodilation, reducing systemic vascular resistance and lowering blood pressure. Primary indications include hypertension and vasospastic (Prinzmetal) angina. Amlodipine has a long half-life (~30–50 hours), allowing once-daily dosing and a gradual onset that limits reflex tachycardia. Nifedipine, especially in immediate-release form, acts rapidly and can trigger significant reflex sympathetic activation — tachycardia, flushing, and headache — which is why immediate-release nifedipine is no longer recommended for hypertensive urgency. Extended-release nifedipine avoids this spike. The most common adverse effect across the class is peripheral (ankle) edema from preferential arteriolar dilation. Because these drugs do not suppress the SA or AV node, they are NOT used for rate control in atrial fibrillation or other arrhythmias — that territory belongs entirely to the non-dihydropyridines.

Key Distinctions

Don't confuse dihydropyridines (vascular selective, no rate control) with non-dihydropyridines (cardiac selective, slow heart rate). Students often assume all CCBs slow the heart — dihydropyridines can actually increase heart rate reflexively. Immediate-release nifedipine is dangerous in hypertensive urgency due to unpredictable, precipitous BP drops; extended-release is the safe formulation.

Clinical Pearl

Think "DHP = Drops Hypertension Peripherally." These drugs dilate arteries, not slow the heart. If the question wants rate control, DHP is the wrong answer.