The Effects of Bunazosin and Metoprolol on The Morning Rise of Blood Pressure and Heart Rate in Patients with Essential Hypertension

The purpose of this study was to evaluate the effects of bunazosin, α1-aradrenoreceptor blocking agent and metoprolol, a β1-selective beta-blocker on the circadian variation and morning rise of blood pressure (BP) and heart rate (HR). In 26 untreated patients with mild to moderate essential hypertension, BP and HR were recorded using an ambulatory instrument (ABPM-630, Nippon Colin, Japan) for 48 hours every 30 minutes, before and after four weeks of treatment with bunazosin (n=12, 1 mg three times a day) or metoprolol (n=14, 40 mg three times a day). Mean 48-hour, daytime (awake), and nighttime (sleeping) systolic BP (SBP), diastolic BP (DBP) and HR values were analyzed by reviewing the patients' diaries. The nocturnal reduction rate of SBP, DBP and HR were calculated according to the following formula. Nocturnal reduction rate (%) = [(daytime mean-nighttime mean) /daytime mean] ×100. And then, “morning rise” of SBP, DBP and HR in the second day were calculated. Morning rise = [(mean values of 4 hours after awaking)-(mean values of 4 hours before awaking)]. In the pretreatment 48-hour mean, bunazosin lowered SBP by 6.8±4.4% (p<0.001) and DBP by 7.1±4.7% (p<0.001), but did not change HR. Metoprolol decreased the 48-hour mean of SBP by 6.1±4.9% (p<0.001), DBP by 9.1±5.7% (p<0.001) and HR by 12.3±7.4% (p<0.001). Nocturnal reduction rates of SBP and DBP showed no significant changes in either group.The morning rise of HR increased with bunazosin (p<0.05), but the morning rise of SBP, DBP and HR were significantly decreased with metoprolol (p<0.05).These findings suggest that metoprolol causes reduction of morning rise of BP and HR without a significant change in circadian BP profile.