Calcium channel blockers: Is it time to split the lump?

Antihypertensive drug classes such as thiazide diuretics, angiotensin-converting enzyme inhibitors, β-adrenergic blocking agents, peripheral α1-antagonists, and central α2-agonists all describe therapeutic agents that are quite similar to each other and strikingly different from members of the other classes. A glaring exception is the rubric “calcium channel blocker,” under which strikingly dissimilar drugs have been lumped. Although the phenylalkylamines (verapamil and gallapamil) and benzothiazepines (diltiazem and TA3090) bind at different receptors on the α1 component of the calcium channel, they are reasonably similar in their clinical pharmacology. For example, both types of drugs slow the heart rate and there are intravenous preparations that are used to treat supraventricular tachycardia. The dihydropyridines (nifedipine and many others) bind to another receptor on the α1 component, but have markedly different pharmacologic properties. For example, they tend to increase the heart rate, do not cause constipation, but are more likely to cause peripheral edema. I propose that we refer to this entire class of drugs as “calcium antagonists,” that we continue to refer to verapamil, diltiazem, and similar drugs as “calcium channel blockers,” but recognize the very different properties of nifedipine and like drugs by referring to them as dihydropyridines or DHPs.