Design, statistical analysis and sample size calculation of dose response study of telmisartan and hydrochlorothiazide

Many patients with hypertension take some antihypertensive drugs with complementary mechanisms of action to lower their blood pressure and achieve the therapeutic goals reducing the risk of cardiovascular events. Telmisartan, angiotensin II receptor blocker, and hydrochlorothiazide, diuretic are two antihypertensive drugs that have a well-recognized clinical efficacy. Their combination is expected to be one of the most appropriate therapies for hypertensive patients. However there is no information to show the effective dose combination of two drugs for the Japanese patients with mild to moderate hypertension. Therefore, the prospective, randomized, double-blinded study was planed for showing the dose response surface of two components. The 3 by 3 factorial design was applied for this purpose and the approach for calculating sample size was proposed. This study was registered with ClinicalTrial.gov (NCT00153049).