Effects of amlodipine once-daily administration on blood pressure circadian profile evaluated by noninvasive 24-hour ambulatory blood pressure monitoring: Inferential analysis of an open noncomparative study

Blood pressure (BP) is characterized by a periodical circadian trend, which reflects some hemodynamic and cardiovascular changes. In comparison with office BP measurements, one of the most useful tools to evaluate pressure variability seems to be 24-hour ambulatory blood pressure monitoring (ABPM). To verify the antihypertensive efficacy of amlodipine and its possible influence over the circadian BP profile, we studied 20 patients (12 men, 8 women), mean age 49 years, who were affected by mild-to-moderate essential hypertension (supine and standing diastolic BP = 95 to 114 mmHg). After a 2-week pharmacologic washout period and at the end of 26 weeks of treatment with amlodipine (10 mg once daily), the patients underwent ABPM with a Spacelabs 90207. During this period, timely clinical and laboratory tests were done to evaluate the office BP and possible side effects. The data obtained were interpretated by "traditional" statistical methods and by inferential analysis (statistical study of mathematical functions, deriving from original series extrapolation), by means of Fourier model with four harmonics. BPs were significantly reduced by amlodipine over 24 hours without significant changes in heart rate (HR). BP fell during the night and the slope of BP morning rose--time of maximum incidence of myocardial ischemia and stroke-appeared to be significantly controlled by amlodipine. These results confirm that amlodipine can be considered a first-choice drug in patients with cardiovascular risk factors because of its role in BP day-long control, particularly at awakening. Once-daily administration and few drug side effects enhanced patient compliance and allowed more satisfying therapeutic results. The four harmonics Fourier model could improve the traditional statistical methods for 24-hour ABPM interpretation, for a correct evaluation of BP long-term variability.