Ethnic differences in blood pressure response to first and second-line antihypertensive therapies in patients randomized in the ASCOT Trial.

Background: Some studies suggest that blood pressure (BP)-lowering effects of commonly used antihypertensive drugs differ among ethnic groups. However, differences in the response to second-line therapy have not been studied extensively.
Methods: In the BP-lowering arm of the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT-BPLA), BP levels of European (n = 4,368), African (203), and South-Asian- (132) origin patients on unchanged monotherapy (atenolol or amlodipine) and/or on second-line therapy (added thiazide or perindopril) were compared. Interaction between ethnicity and BP responses (defined as end BP minus start of therapy BP) to both first- and second-line therapies were assessed in regression models after accounting for age, sex, and several other potential confounders.
Results: BP response to atenolol and amlodipine monotherapy differed among the three ethnic groups (interaction test P = 0.05). Among those allocated atenolol monotherapy, black patients were significantly less responsive (mean systolic BP (SBP) difference +1.7 (95% confidence interval: -1.1 to 4.6) mm Hg) compared to white patients (referent). In contrast, BP response to amlodipine monotherapy did not differ significantly by ethnic group. BP responses to the addition of second-line therapy also differed significantly by ethnic group (interaction test P = 0.004). On adding a diuretic to atenolol, BP lowering was similar among blacks and South-Asians as compared to whites (referent). However, on addition of perindopril to amlodipine, BP responses differed significantly: compared to whites (SBP difference -1.7 (-2.8 to -0.7) mm Hg), black patients had a lesser response (SBP difference 0.8 (-2.5 to 4.2) mm Hg) and South-Asians had a greater response (SBP difference -6.2 (-10.2 to -2.2) mm Hg).
Conclusions: We found important differences in BP responses among ethnic groups to both first- and second-line antihypertensive therapies.