The objective of this trial is to demonstrate that the fixed dose combination of telmisartan 40 mg and HCTZ 12.5 mg is superior to the monocomponent of telmisartan (Micardis, Gliosartan, Kinzal, Kinzalmono, Predxal, Pritor, Samertan, Telmisartan) 40 mg in patients with essential hypertension who fail to respond adequately to telmisartan monotherapy.

This is a multi-centre, randomised, double-blind, double-dummy, active-controlled, parallel-group study in patients with essential hypertension who fail to respond adequately to telmisartan (Micardis) 40 mg monotherapy.

After a screening and a 2-week washout period (screening period), the patients will enter 4-week open-label run-in period with telmisartan (Micardis) 40 mg monotherapy to assess eligibility. The study will be terminated for those who have responded to telmisartan (Micardis) 40 mg monotherapy at the end of 4-week open-label run-in period with telmisartan (Micardis) 40 mg monotherapy (mean seated DBP < 90 mmHg). About 200 patients not responding adequately to telmisartan (Micardis) 40 mg monotherapy will be randomised and treated for 8 weeks with once-daily administration of either telmisartan (Micardis) 40 mg or a fixed dose combination of telmisartan 40 mg and HCTZ 12.5 mg (double-blind treatment period).

Study Hypothesis:

The hypothesis is that the fixed dose combination of telmisartan 40 mg and HCTZ 12.5 mg is superior to the monocomponent of telmisartan (Micardis) 40 mg in pat ient with essential hypertension who fail to respond adequately to telmisartan monotherapy.

Comparison(s):

For the primary comparison the change from baseline in mean stated trough DBP at the end of the 8-week double-blind treatment will be expressed.

Inclusion Criteria:

• Essential hypertensive patients who meet all the criteria as follows:

  • Mean seated DBP must be >= 95 and <= 114 mmHg at Visit 2
  • Mean seated SBP must be >= 140 and <= 200 mmHg at Visit 2
  • Mean seated DBP must be >= 90 and <= 114 mmHg at Visit 3
  • Mean seated SBP must be <= 200 mmHg at Visit 3

Exclusion Criteria:

• Patients taking 4 or more anti-hypertensive medications at Visit 1
• Patients with known or suspected secondary hypertension (renovascular hypertension, primary aldosteronism, pheochromocytoma, etc.)