Efficacy of transdermal nitroglycerin patches evaluated by dipyridamole-induced myocardial ischemia in patients with coronary artery disease. Comparison between continuous and intermittent schedule.

Nitrate tolerance remains a problem despite an enormous number of studies on this phenomenon. The aim of the present study was to compare the efficacy of nitroglycerin transdermal patches intermittently or continuously administered to patients with myocardial ischemia evaluated by the echocardiography dipyridamole stress test. We prospectively studied 34 coronary patients with stable myocardial ischemia. A double-blind, randomized, crossover study technique was used. After a run-in period (1 week) they underwent a dipyridamole stress test to evaluate nitrate responsiveness and then were randomized to 1 week of transdermal nitroglycerine 20 mg/24 h (two patches of 10 mg/24) administered either intermittently or continuously for 1 week. During the following week all patients were given placebo. In the final week, therapy was crossed over the alternate regimen. No significant changes in heart rate, systolic and diastolic blood pressure and rate-pressure product were observed at basal conditions and at peak of dipyridamole infusion among patients after placebo run-in period, after acute, 1 week of intermittent and 1 week of continuous nitroglycerine administration. At peak of dipyridamole infusion after acute administration of nitrate we observed a significant decrease in wall motion score index with respect to placebo. This pattern was similar during intermittent, but not continuous, patch therapy (p < 0.001). Our results suggest that transdermal nitroglycerin patches are an effective anti-ischemic medication, in reducing transient myocardial ischemia induced by dipyridamole. This anti-ischemic effect is lost when an overnight nitrate free dose interval is not used. Moreover the dipyridamole echocardiographic stress test, besides evaluating myocardial ischemia-induced wall motion abnormalities, is adequate to assess both the efficacy and the tolerance of transdermal nitrate therapy.