There are important pharmacologic differences among calcium channel antagonists. Knowledge of these properties is helpful when selecting a drug for a given patient, and for avoiding potential toxicities.
Are the calcium channel antagonists interchangeable?
No. Although they belong to the same broad category, there are distinct subclassifications. The major approved indications for these agents are summarized in the table below. The sustained-release preparations often do not have the same indications as the shorter-acting preparations.
Name some contraindications to the use of calcium channel antagonists.
In addition to known hypersensitivity reactions, contraindications are related to the pharmacologic properties of the various subclasses, including hypotension, congestive heart failure, sick-sinus syndrome, and second- or third-degree atrioventricular (AV) block. Because of significant vasodilatation and lowering of vascular resistance, the dihydropyridine subclass is avoided in patients with severe aortic stenosis and hypertrophic cardiomyopathy. Bepridil prolongs QT intervals, is contraindicated in patients with a history of serious ventricular arrhythmias, and is reserved for patients with angina that does not respond to other medications.