The use of
calcium antagonists for the treatment of patients with
unstable angina and acute
myocardial infarction has been a promising area of both basic and clinical research. Despite consistently beneficial effects experimentally, the clinical extrapolation of these results has been less than ideal, especially in patients with evolving
myocardial infarction.
Calcium antagonists have in some instances failed to manifest benefit and at times have been shown to have negative effects. One reason for this could be the use of oral or sublingual preparations, which result in variable absorption, variable volumes of distribution, and variable clearance. For this reason, an intravenous preparation of one of the
calcium antagonists,
diltiazem, may be more beneficial. Such a preparation has been developed and its safety confirmed in patients without
cardiovascular disease and in patients with acute
infarction. Substantial benefit has been documented in patients with
stable angina and during noncardiac surgery. Preliminary data in patients with
unstable angina suggest that the
drug is effective, although studies comparing intravenous
diltiazem with other agents or with the oral preparation of
diltiazem have not yet been reported. Experimental data in animals with acute
infarction have demonstrated that administration of intravenous
diltiazem after occlusion, but prior to reperfusion, elicits a marked increase in the degree of myocardial salvage induced by thrombolysis. This appears to be due to the inhibition of lipid peroxidation rather than alterations in coronary perfusion. Thus, it appears that the intravenous preparation may permit the more effective use of
diltiazem in patients with acute
coronary artery disease.