Chronobiologic Evaluation of Captopril-Retard Twice a Day in Essential Hypertension: In Comparison with Captopril Three Times a Day.

The purpose of this study was to evaluate the efficacy of captopril-retard (C-R) and captopril (C) chronobiologically in patients with essential hypertension. Doses of C-R of 18.75mg twice a day and C of 12.5-25mg three times a day were administered at least 6wk in each of 9 patients. The blood pressure (BP) monitoring was repeated before and after the treatment for 48hr every 30min with an ambulatory instrument (ABPM-630, Nippon Colin, Japan). These data were analyzed with conventional statistical and cosinor methods. The hyper- and hypobaric indices of BP were calculated based on our reference limits. The least square fit of a cosine curve with a period of 24hr was calculated to obtain a midline estimating statistic of rhythm (MESOR), amplitude, and acropase. A circadian rhythm cycle of about 24hr was found in the BP in all cases. C-R lowered MESOR of systolic BP (SBP) and diastolic BP (DBP) from 134.6±9.7mmHg to 129.9±9.9mmHg and 77.4±4.3mmHg to 70.2±5.7mmHg (P<0.01), and C decreased MESOR of DBP and DBP from 138.1±11.1mmHg to 129.0±8.8mmHg and 78.5±8.5mmHg to 72.5±7.0mmHg, respectively (P<0.01). The hyperbaric index of SBP significantly decreased with C-R and C (P<0.05). However, the amplitude and acrophase of BP showed no significant changes in either group. In conclusion, C-R and C showed definite antihypertensive effect, preserving the circadian rhythm of BP similarly.