We performed a prospective, randomized, multicenter, parallel-group, per-protocol study to compare the effects of hydrochlorothiazide (HCTZ) and amlodipine as add-on to losartan treatment in hypertensive type 2 diabetic patients. A total of 49 Japanese type 2 diabetic patients with inadequate control of blood pressure while receiving losartan 50 mg were randomly allocated to receive a fixed-dose single-pill combination of HCTZ 12.5 mg plus losartan (N = 26) or a free combination of amlodipine 5 mg plus losartan (N = 23). During 8 weeks of follow-up, changes in blood pressure and laboratory data including HbA1c, uric acid, and potassium were compared between the groups using analysis of covariance. Systolic and diastolic blood pressure decreased in both groups, the reductions of which were greater in the amlodipine group. However, the least square mean (95 % CI) differences between groups were not statistically significant [2.3 (-6.8 to 11.4) mmHg, p = 0.618 and 2.7 (-2.4-7.9) mmHg, p = 0.293, respectively]. HbA1c increased in patients receiving HCTZ but not in the amlodipine group. Uric acid also increased in patients receiving HCTZ but decreased in patients receiving amlodipine, yielding a significant between-group difference of 1.0 (0.5-1.5) mg/dl (p < 0.001). No intra- or intergroup change was observed in serum potassium levels. This pilot study suggests that HCTZ and amlodipine result in nonsignificant effects on systolic and diastolic blood pressure reduction when administrated as add-on therapy to losartan in hypertensive patients with type 2 diabetes; however, addition of HCTZ may be associated with less favorable effects on metabolic profiles than amlodipine.
Keywords: Amlodipine; Diabetes; Hydrochlorothiazide; Hypertension.