Comparative Study of the Effects of Amlodipine and Nitrendipine on 24-Hour Blood Pressure Profile

Abstract

The aim of this study was to evaluate the antihypertensive efficacy and duration of action of amlodipine and nitrendipine by means of 24-hour ambulatory blood pressure monitoring. 35 patients with mild to moderate arterial hypertension, aged 36 to 64 years, were enrolled in a randomised 24-week crossover study. After a 2-week run-in period, patients with confirmed hypertension (diastolic blood pressure 95 to 115mm Hg) were randomised to treatment with either amlodipine 5mg or nitrendipine 20mg once daily, with dosage adjustment (to amlodipine 10mg and nitrendipine 40mg once daily) permitted after the second week if blood pressure control (diastolic pressure < 90mm Hg) was not achieved. After 12 weeks of therapy, the 2 subgroups crossed over to the alternative treatment. Active treatment was continued for a further 12 weeks, with dosage adjustment permitted after the second week, as previously. Ambulatory blood pressure monitoring was performed at the end of the run-in period and after 12 weeks of each phase of treatment. Systolic blood pressure, measured by standard mercury sphygmomanometry, decreased significantly by a mean of 23.4mm Hg and 19.6mm Hg after 12 weeks’ treatment with amlodipine and nitrendipine, respectively; diastolic blood pressure decreased significantly by 18.4mm Hg and 14.0mm Hg with amlodipine and nitrendipine, respectively. Heart rate was unchanged. Ambulatory blood pressure monitoring showed a significant blood pressure reduction when evaluated in a descriptive time-fixed way, with means and standard deviations calculated every hour after the end of the 2 treatments, and in a qualitative way through Fourier analysis. The blood pressure reduction was confirmed by the decrease in the mean level parameter obtained through Fourier analysis, while clinically insignificant changes in the phase, amplitude and speed variables, indicative of unaltered circadian rhythm, were reported during treatment with both drugs. Both amlodipine and nitrendipine were shown to exert appreciable antihypertensive activity, which persisted over the 24-hour dose interval and was sustained for the study duration. Dosage increment after the second week of therapy was required less often with amlodipine (43.0% of patients) than with nitrendipine (62.9%).