Trough and peak effects of a single daily dose of nifedipine gastrointestinal therapeutic system (GITS) as assessed by ambulatory blood pressure monitoring. Italian Nifedipine GITS Study Group.

AIM

To evaluate the antihypertensive efficacy of nifedipine gastrointestinal therapeutic system (GITS), a slow-release formulation of nifedipine.

PATIENTS AND METHODS

A randomly allocated, double-blind, placebo-controlled trial was set up with 126 essential hypertensives who were assessed by ambulatory blood pressure monitoring. A 2-week placebo run-in phase was followed by treatment with nifedipine GITS at 30 mg (n = 42) or 60 mg (n = 42) or with a placebo (n = 42) once a day for 4 weeks. At the end of each period, 24- to 36-h ambulatory blood pressure was measured at 15-min intervals by a SpaceLabs 90202 or 90207 device. The peak effect of nifedipine was assessed as the lowest average hourly value of systolic/diastolic blood pressure 2-6 h after drug intake subtracted from the baseline value for the same hour, and the trough effect as the mean systolic/diastolic blood pressure obtained 24 h after the dose subtracted from the baseline value for the same hour.

RESULTS

In the 81 patients with 24-h valid ambulatory blood pressure data, 24-h, daytime and night-time mean systolic and diastolic blood pressures were significantly decreased by nifedipine GITS at both doses, but were not changed by the placebo. The trough: peak ratios for systolic and diastolic blood pressure were 90.5 and 76.3% for 30 mg nifedipine GITS and 109.3 and 98.6% for 60 mg nifedipine GITS. Correction by trough and peak effects in the placebo group further increased the trough: peak ratios. In 51 patients with 36-h ambulatory blood pressure data, trough: peak ratios above the United States Food and Drug Administration recommended value of 50% were found 30 h after the dose, and systolic blood pressure was still significantly lower 36 h after the nifedipine GITS dose.