Effect of imidapril in dipper and nondipper hypertensive patients: Comparison between morning and evening administration

The purpose of the study was to identify differences in the patterns of eff icacy and duration of effects of imidapril administered at different times of the day (morning versus evening) in dipper and nondipper hypertensive pa tients. Twenty patients with untreated hypertension were classified into tw o groups: dippers (n = 9) and nondippers (n = 11). Imidapril (10 mg) was gi ven at 07:00 or 18:00 for 4 weeks in a crossover fashion. Blood pressure (B P) and heart rate (HR) were monitored before and after morning and evening treatment every 30 min for 48h by ambulatory BP monitoring (ABPM). In dippe r hypertension, the mean 48h BP was reduced with both doses. The decrease i n the diurnal BP was stronger when the drug was administered in the evening than morning, but without significant difference. In nondipper hypertensio n, the systolic BP decreased at night with both doses, but the extent of th e nocturnal reduction in systolic BP was greater after morning therapy. The re were no significant differences in the decrease in BP during the day or night between the morning and evening administrations. When imidapril was a dministered in the morning, its serum concentration reached a maximum at 16 :00, and when the drug was administered in the evening, it reached a maximu m at 6:00. In dipper hypertension, the time taken for the blood concentrati on of imidapril to reach a maximum changed depending on its time of adminis tration, and the time when the maximum antihypertensive effect of the drug appeared was different. In nondipper hypertension, decreases in the BP were confirmed at night regardless of the time of administration; this might be caused by angiotensin converting enzyme (ACE) inhibitors effectively block ing the BP from increasing by activating the parasympathetic nervous system . Therefore, when assessing the effectiveness of antihypertensive agents, f actors such as the various patterns of BP before therapy and administration time must be considered.