Nifedipine gastrointestinal therapeutic system in the treatment of hypertension. Results of a multicenter trial. The Modern Approach to the Treatment of Hypertension (MATH) Study Group. Nifedipine, in the gastrointestinal therapeutic system (GITS) formulation, a controlled-release formulation for once-a-day administration, was evaluated in the Modern Approach to the Treatment of Hypertension (MATH) trial. In this study conducted at 127 centers, 1155 patients with mild-to-moderate hypertension representative of the spectrum seen in practice were included in the analyses of effectiveness. After a 2 week placebo period, nifedipine GITS therapy was started at 30 mg/day and was titrated to a maximum dose of 180 mg/day over 6 weeks. Response criteria were a sitting diastolic blood pressure less than 90 mm Hg and a decrease of greater than or equal to 10 mm Hg. After titration, patients were observed for 12 weeks during treatment. At the final visit, nifedipine GITS significantly (P less than .0001) reduced sitting systolic blood pressure 17 +/- 14 mm Hg (mean +/- SD), and sitting diastolic blood pressure 14 +/- 8 mm Hg. Similar highly significant reductions in standing blood pressure were observed. For all subjects, 76% achieved goal blood pressure response during titration. More than 50% were controlled on doses of 30 to 60 mg/day. At the final visit blood pressure reductions in men and women were similar, except for a significantly greater decrease in sitting systolic pressure for women. A similar proportion of blacks responded compared with whites, and reductions in sitting systolic and diastolic blood pressure were also similar in the 2 groups. Nifedipine GITS had no effect on renal function, serum potassium, or total, HDL, or LDL cholesterol. Uric acid was reduced by 0.5 mg/dL (P less than .001). 