Safety of acute calcium antagonist withdrawal: Studies in patients with unstable angina withdrawn from nifedipine

The acute effects of nifedipine withdrawal were studied in 81 patients with angina at rest who had completed a prospective, double-blind, randomized trial of nifedipine versus placebo. Thirty-nine of the 81 patients (group 1) were withdrawn from nifedipine or placebo at the time of coronary artery bypass surgery for uncontrolled angina or left main coronary artery disease. When the patients withdrawn from nifedipine were compared with those withdrawn from placebo, no significant differences were seen in the incidence of hypotension, myocardial infarction, significant arrhythmias or vasopressor or vasodilator requirements during the perioperative period. Forty-two patients (group 2) completed 2 years on a protocol consisting of nitrates and propranolol, in addition to nifedipine or placebo. These patients were hospitalized for a controlled withdrawal of the study drug (nifedipine or placebo), and no significant difference was noted in either exercise performance on serial treadmill testing or the number or duration of episodes of ischemic ST-segment changes during continuous electrocardiographic monitoring. Eight patients continued to experience occasional episodes of angina at rest. Angina at rest recurred during the withdrawal period in 5 of these 8 patients. Four of these 5 patients were withdrawn from nifedipine. Of the 34 stable patients in group 2 who were not experiencing angina at rest before withdrawal, none had angina at rest during the withdrawal study period. Thus, there were no early untoward effects of acute nifedipine withdrawal either in patients undergoing coronary bypass surgery or in stable patients on long-term medical therapy. However, patients with persistent symptoms of angina at rest may experience early recurrent ischemia upon withdrawal from nifedipine.