Background: This study investigated whether a combination drug containing an angiotensin II receptor blocker (ARB) and a calcium channel blocker (CCB) could provide effective antihypertensive therapy.Methods: A multicenter, prospective, open-label study was conducted at the clinics of Clinical Research Network. The subjects had uncontrolled blood pressure (BP) despite ARB or CCB monotherapy. The effect on both office and home BP was examined after patients switched to a combination drug (REZ: containing 20 mg of olmesartan [OL] and 16 mg of azelnidipine [AZ]).Results: A total of 78 patients were enrolled. After switching to REZ, a significant and sustained reduction of office BP was observed. The proportion of patients who achieved the target for both office and home BP was an increase from 0% to 55%. Switching from amlodipine to REZ resulted in a significant and sustained decrease of office and home BP. There was also a significant decrease of home pulse rate (PR), but office PR was unchanged. To determine the accuracy of the BP and PR values reported by patients, the frequency of each number as the first digit was determined. The frequency of "0" was extremely high for both office and home BP values, and the same was noted for home PR values.Conclusion: The results of this study suggested that switching from a single drug to combination therapy with REZ could achieve a stronger antihypertensive effect. However, concern was raised regarding the methods of BP and PR measurement and recording in this clinical trial involving general practitioners.
Keywords: Hypertension; angiotensin II receptor blocker; calcium channel blocker; combination drug; multicenter prospective study.