• Change from baseline in sitting diastolic blood pressure (DBP) at trough (24 hours post-dosing) at the last observation during the double-blind phase.
  

• Change from baseline in sitting SBP, standing DBP, standing SBP, sitting and standing heart rate at trough as well as blood pressure control and blood pressure response as defined in study protocol at the last observation will be evaluated.
  

This is a randomised, double-blind, double-dummy, parallel-group study in mild to moderate hypertensive patients treated for eight weeks with either telmisartan 40mg / hydrochlorothiazide 12.5mg or losartan 50mg/ hydrochlorothiazide 12.5mg.

The study will be divided into two phases:

(i) Placebo Run-in Phase (Visit 1 to Visit 2, day -14 (~ day -21) to day 1): Initial screening and withdrawal of current anti-hypertensives is followed by a two week placebo phase with dummy telmisartan 40mg / hydrochlorothiazide 12.5mg and dummy losartan 50mg / hydrochlorothiazide 12.5mg. Baseline assessments are done at the end of the 2 week run-in phase (at Visit 2, day 1).

(ii) Treatment Phase (Visit 2 to 4, day 1 to day 57): This is an eight-weeks double-blind, double-dummy parallel trial with telmisartan 40mg / hydrochlorothiazide 12.5mg or losartan 50mg / hydrochlorothiazide 12.5mg. Final assessments are done at the end of the eight-weeks treatment phase at Visit 4.

Study Hypothesis:

Null and alternative hypothesis The change from baseline in sitting diastolic blood pressure at trough (24 hours post-dosing) at the last visit during the double-blind phase defines the primary endpoint. This trial is to test the non-inferiority of efficacy of telmisartan 40mg / hydrochlorothiazide 12.5mg to losartan 50mg / hydrochlorothiazide 12.5mg. A difference of 3mmHg in reducing sitting diastolic blood pressure would be considered clinically significant.

H0: (Reduction from baseline in sitting diastolic blood pressure at trough of losartan 50mg / hydroclorothiazide 12.5mg group) - (Reduction from baseline in sitting diastolic blood pressure at trough of telmisartan 40mg / hydrochlorothiazide 12.5mg group) > 3 mmHg HA: (Reduction from baseline in sitting diastolic blood pressure at trough of losartan 50mg / hydroclorothiazide 12.5mg group) - (Reduction from baseline in sitting diastolic blood pressure at trough of telmisartan 40mg / hydrochlorothiazide 12.5mg group) ? 3 mmHg

Comparison(s):

Change from baseline in sitting diastolic blood pressure (DBP) at trough (24 hours post-dosing) at the last observation during the double-blind phase.

A 24-hour post-dose timepoint at the last visit of the run-in phase will be specified as the baseline trough measurement.