The Phase III, double-blind, parallel-group controlled study of amlodipine 10 mg once daily in Japanese patients with essential hypertension who insufficiently responded to amlodipine 5 mg once daily.

The objective of this Phase III double-blind parallel-group controlled study was to examine the superiority of amlodipine 10 mg once daily (the amlodipine 10 mg group) to amlodipine 5 mg once daily (the amlodipine 5 mg group) in 305 Japanese outpatients with essential hypertension whose systolic blood pressure (SBP) had not reached the therapeutic target levels (<130-140/80-90 mm Hg) when treated with amlodipine 5 mg once daily. This study consisted of the 1-week prescreening, 8-week screening and 8-week double-blind periods. Changes in trough SBP from baseline at week 8 of the double-blind period (week 8) were -7.0 mm Hg and -13.7 mm Hg in the amlodipine 5 and 10 mg groups, respectively; a significant difference (P<0.001) was found between the two groups. Changes in trough diastolic blood pressure (DBP) from baseline at week 8 were -2.7 mm Hg and -6.8 mm Hg in the amlodipine 5 and 10 mg groups, respectively, with a significant difference (P<0.001) between the two groups. At week 8, responder rates were 28.5 and 44.0% in the amlodipine 5 mg and 10 mg groups, respectively, with a significant difference (P=0.002) between the two groups. The amlodipine 10 mg group showed no significant difference in the incidences of adverse events against the amlodipine 5 mg group. The incidence of mild peripheral oedema was 4% only in the amlodipine 10 mg group. In conclusion, amlodipine 10 mg once daily was found to be superior to amlodipine 5 mg once daily, safe, well tolerated and useful for the relevant subjects.