Twenty-four hour ambulatory blood pressure in the International Nifedipine GITS Study Intervention as a Goal in Hypertension Treatment (INSIGHT)

Objectives: The International Nifedipine GITS Study Intervention as a Goal in Hypertension Treatment (INSIGHT) showed, by means of office blood pressure measurements, that long-term treatment with nifedipine GITS is as effective as diuretics in preventing cardiovascular and cerebrovascular complications. However, since office blood pressure measurements reflect to a limited extent blood pressure outside the office, a side-arm INSIGHT study in which patients underwent both office measurement and 24 h ambulatory blood pressure monitoring was also performed. Design and methods: The study had a randomized, double-blind, parallel group design. After 4 weeks of placebo, mild-to-moderate essential hypertensive patients were randomized to nifedipine GITS 30 mg or amiloride 2.5 + hydrochlorothiazide 5 mg for 3.1 years. Dose titration was performed by dose doubling and addition of atenolol 25-50 mg or enalapril 5-10 mg, or other drugs when needed. Analysis was carried out by intention-to-treat and included computation of 24 h, day and night ambulatory blood pressure and heart rate values. Additional analyses included computation of the trough-to-peak ratio and the smoothness index (the ratio between the average of the 24-hourly blood pressure reductions after treatment and its standard deviation). Results: A total of 151 patients were recruited and 149 were valid for analysis: 78 patients had 24 h ambulatory recordings both at baseline and during treatment and 134 during treatment. Office, 24 h and day and night blood pressures were all significantly and similarly reduced by both treatments. Office and ambulatory heart rate was left unchanged by diuretics, while it was slightly reduced by nifedipine. Median trough-to-peak ratios were always > 0.5 and superimposable between the two treatment groups. Similarly, smoothness indices of systolic and diastolic blood pressures were comparably high for nifedipine and diuretics, thus demonstrating a similar well-balanced antihypertensive response to both drugs. No significant differences were observed between the two treatment groups in the number of cardiovascular events (17 in the nifedipine-based and 26 in the diuretics-based treatment group). Conclusions: In the INSIGHT study, the long-term antihypertensive effect on 24 h blood pressure and the cardiovascular protection of nifedipine was similar to that of diuretics