Comparisons of Increasing Calcium Channel Blocker dose and Adding Thiazide Diuretic in Hypertensive Patients Given Medium-dose Angiotensin II Receptor Blocker and Amlodipine

We compared the efficacies of 2 prescriptions, one of a medium-dose angiotensin II receptor blocker （ARB） with high-dose of calcium channel blocker （CCB） and another of medium-dose of ARB with medium-dose of CCB and a thiazide diuretic in 22 hypertensive patients who did not achieve the target blood pressure level with the combination of medium-dose of ARB and medium-dose of CCB. A randomized crossover study was performed giving a fixed combination of 100 mg irbesartan with 10 mg amlodipine or a fixed-dose combination of 100 mg irbesartan with 5 mg amlodipine added by 1 mg trichlormethiazide for 12-16 weeks each. The blood pressure measured in hospital was comparable between the high-dose CCB period （130/77 mmHg） and the thiazide period （130/79 mmHg）. The morning and the evening blood pressures measured at home were also comparable in the high-dose of CCB and the thiazide periods, while the evening heart rate was higher in the thiazide period than in the high-dose CCB period. As for the laboratory data, hemoglobin A1c （＋0.2％, p＝0.013）, serum nonHDL cholesterol （＋12 mg/dL, p＝0.047） and serum uric acid （＋0.8 mg/dL, p＝0.001） were significantly higher in the thiazide period than in the high-dose CCB period. On the other hand, urinary albumin excretion （－28.8％，p＝0.026） and estimated glomerular filtration rate （－5.8％，p＝0.012） were significantly lower in the thiazide period than in the high-dose CCB period. In the combination drug therapy of hypertension, the increase of CCB dose is preferable in preserving renal function and in avoiding adverse effects on metabolisms of glucose, lipid and uric acid