Effect of morning versus evening dosing of diltiazem on myocardial ischemia detected by ambulatory electrocardiographic monitoring in chronic stable angina pectoris. Dilacor XR Ambulatory Ischemia Study Group.

Myocardial ischemia occurs frequently during daily life and has a circadian pattern similar to that reported for myocardial infarction and sudden death. Because of the increased risk of myocardial ischemia in the morning hours, it has been suggested that the administration of anti-ischemic medication before bedtime may be more effective than the traditional morning dosing. This randomized, double-blind, placebo-controlled, crossover study evaluated the effects of 480-mg/day diltiazem (given either in the A.M. or the P.M.) on myocardial ischemia using ambulatory electrocardiographic monitoring in 68 patients with chronic stable angina and > or = 2 minutes of ischemia per 48 hours. During treatment with diltiazem, the duration and number of myocardial ischemic episodes were reduced by 45% (94 to 52 minutes, p <0.004) and by 40% (4.5 to 2.7 episodes, p <0.003), respectively. The duration and number of myocardial ischemic episodes during daytime (6 A.M. to 6 P.M.) hours were also reduced by 52% (74 to 36 minutes, p <0.002) and by 48% (3.1 to 1.6 episodes, p <0.001), respectively. There was no significant difference between A.M. and P.M. dosing. Morning ischemia (6 A.M. to noon), considered separately from daytime ischemia, was also significantly reduced by both A.M. and P.M. dosing regimens, with no difference between the regimens. The results of this study showed that both A.M. and P.M. dosing of long-acting diltiazem were equally effective in suppressing episodes of ambulatory myocardial ischemia at all times.