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

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.