Fifteen patients with coronary artery spasm completed a double-blind placebo-controlled trial comparing diltiazem and nifedipine. Increasingly, higher daily doses (diltiazem, 90 to 360 mg; nifedipine, 30 to 120 mg) were administered to achieve optimal clinical effects. Daily diaries and ambulatory electrocardiographic recordings were used to assess efficacy and side effects. Both drugs significantly decreased angina frequency compared with that in the preceding placebo period (diltiazem 1.4 +/- 0.4 [mean +/- SEM] to 0.4 +/- 0.2 episodes per day; nifedipine 1.4 +/- 0.3 to 0.4 +/- 0.1 episodes per day; both p less than 0.05). Ambulatory electrocardiographic recordings showed fewer ST shifts than were expected during all treatment periods (0.02/h recorded during placebo, none during diltiazem and 0.02/h during nifedipine therapy). Although some patients responded better to one drug than the other, neither drug resulted in a clearly superior clinical response. Diltiazem was discontinued in one patient because of urticaria, but the total number of side effects was higher with nifedipine (12 of 15 patients) than with diltiazem (5 of 15, p less than 0.01). Nine patients remained symptomatic on single drug treatment and entered open label treatment with the combination of diltiazem and nifedipine. Three patients did not tolerate the combination because of important side effects; the other six also had side effects, but these were relatively minor. Four patients received no more benefit from the combination than from a single agent; the condition of two patients improved. Both diltiazem and nifedipine provide effective antianginal therapy for coronary spasm, but diltiazem has fewer side effects.(ABSTRACT TRUNCATED AT 250 WORDS)

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