Conversion from immediate-release to extended-release diltiazem in angina pectoris

This multicenter, open-label, single crossover study examined 195 patients taking an immediate-release diltiazem tablet as chronic stable angina therapy to determine if apparently logical methods of converting them to an extended-release, once-daily formulation were effective. Patients were converted from the immediate-release (Phase I) to an extended-release (Phase II) formulation of diltiazem on a mg-for-mg basis or, when a similar dose was not available, to the next higher 120 mg dose. Weekly angina occurrences and nitroglycerin use, exercise testing at the end of each phase, and ambulatory electrocardiographic monitoring (AEM) during the week prior to the exercise study were evaluated. There was a statistically significant decrease in angina frequency and nitroglycerin consumption during Phase II. In the exercise studies, there was an insignificant increase in time to 1 mm ST-segment depression and total exercise time associated with a statistically significantly lower end-exercise blood pressure and heart rate in Phase II. In those patients who had ischemia during either phase on AEM, total ischemic duration and ischemic episodes were insignificantly lower in Phase II. All observations were similar in the subgroup of patients who were converted mg-for-mg. Adverse reactions were equal. Thus, in converting patients from an immediate- to an extended-release diltiazem formulation for the treatment of symptomatic coronary artery disease, it is reasonable to convert directly to the same or, if not available, the next higher available dose of the extended-release preparation.