The efficacy of a new slow release (SR) diltiazem preparation was assessed in 10 patients with stable effort angina. A double-blind, placebo controlled, randomized, crossover protocol was carried out comparing the effects of diltiazem 60 mg tid and diltiazem SR 120 mg bid on clinical and ergometric parameters. Exercise test was carried out 3 and 12 hours after the last dose of diltiazem or diltiazem SR respectively. Both drug preparations reduced the incidence of positive test, increased the exercise time and the time of onset of ischemic ST depression. The beneficial effects of the drugs appeared to be due to a reduction in myocardial oxygen consumption at the same workload as shown by the lesser value of pressure rate product at submaximal exercise. In conclusion, diltiazem SR at 12 hours after the last administration has the same effectiveness of diltiazem 60 mg at 3 hours
