| Abstrakt: |
Until recently, only three calcium channel antagonists--verapamil, diltiazem and nifedipine--were available for managing cardiovascular disorders such as hypertension and ischemic heart disease. In the past few years, however, several dihydropyridine calcium channel antagonists, including nicardipine, isradipine, felodipine, nimodipine, and amlodipine, have been marketed. Others are currently awaiting FDA approval. In addition, bepridil, which belongs to a new class of calcium channel antagonists, has recently been marketed for refractory angina pectoris. Clinical uses of calcium channel antagonists have been expanded since the 1970s to include management of cardiovascular disorders such as supraventricular arrhythmias, CHF secondary to diastolic dysfunction, and myocardial reinfarction in selected patients. Calcium channel antagonists are also being investigated for prevention of atherosclerosis. Calcium channel antagonists are a heterogeneous group of pharmacologic agents. Differences in tissue selectivity are largely responsible for the variations in hemodynamic and electrophysiologic properties of these agents. Thus, their clinical uses and side effect profiles differ. These differences must be taken into consideration in the selection of the most appropriate agent for a specific indication. Potential advantages of some of the newer dihydropyridine calcium channel antagonists include less frequent dosing (amlodipine and isradipine) and little or no negative inotropic effect (nicardipine, felodipine, amlodipine, isradipine) compared with the prototype calcium channel antagonists. Additional clinical experience with these newer agents is required, however, before their role in the management of cardiovascular disorders can be fully delineated. The availability of sustained-release formulations of verapamil, diltiazem, nifedipine, felodipine, and nicardipine, as well as the recent marketing of calcium channel antagonists with relatively long half-lives (amlodipine and isradipine), makes once- or twice-daily dosing possible with most calcium channel blockers. However, selection of a particular agent will depend on several factors, including clinical efficacy, side effect profile, cost, and patient characteristics such as concomitant disease states and baseline hemodynamic status. |
