Effects of Captopril on Blood Pressure Variation and Circadian Rhythm in Essential Hypertension

Abstract

The purpose of this study was to evaluate the efficacy of captopril chronobiologically in the treatment of essential hypertension. Nine patients with essential hypertension were examined with ambulatory blood pressure (BP) monitoring (Nippon Colin, Japan). The monitorings were repeated before and after the treatment for 48 hr every 30 min. Captopril (12.5-25mg, three times daily) was administered for at least 6 wks. These data were analyzed with conventional statistical method and cosinor method. The hyper-/hypobaric indices of BP and heart rate (HR) were calculated based on the reference limits. The least squares fit of a cosine curve with a period of 24 hr was calculated to obtain MESOR (midline estimating statistic of rhythm), amplitude and acrophase. A circadian rhythm cycle of about 24 hr was found in BP and HR of all cases. MESOR of systolic and diastolic BP decreased from 138.1±1.1 mmHg to 129.0±8.8 mmHg and from 78.8± 8.5 mmHg to 72.5±7.0 mmHg, respectively (P<0.01). The hyperbaric index of systolic BP significantly decreased (P<0.05). MESOR of HR decreased from 73.0±9.5 bpm to 68.6±6.8 bpm (P<0.05). However, amplitude and acrophase of BP and HR showed no significant changes. In conclusion captopril showed definite antihypertensive effect preserving circadian rhythm of BP and HR.