Study to Evaluate the Trough and Peak Effect of Once Daily Telmisartan 80 mg/Hydrochlorothiazide 12.5 mg (Micardis Plus) by Ambulatory Blood Pressure Monitoring (ABPM) in Patients With Mild to Moderate Essential Hypertension

1. Patients taking more than three anti-hypertensive medications at the screening visit.

2. Pre-menopausal women (last menstruation \<= 1 year prior to start of screening):

* Who are not surgically sterile (hysterectomy, tubal ligation).

* Who are NOT practicing acceptable means of birth control or who do NOT plan to continue using an acceptable method throughout the study. Acceptable methods of birth control include IUD, oral, implantable or injectable contraceptives.

3. Any woman:

* Who has a positive urine pregnancy test at screening (Visit 1).

* Who is nursing.

4. Hepatic and/or renal dysfunction as defined by the following laboratory parameters:

* SGPT(ALT) or SGOT(AST) greater than two times the upper limit of normal.

* Serum creatinine \> 3.0 mg/dL (or 265 mmol/L) or creatinine clearance \< 0.6 ml/sec.

5. Clinically relevant hypokalaemia or hyperkalaemia.

6. Uncorrected volume depletion.

7. Uncorrected sodium depletion.

8. Hereditary fructose intolerance.

9. Biliary obstructive disorders, cholestasis or moderate to severe hepatic insufficiency.

10. Known or suspected secondary hypertension.

11. Bilateral renal artery stenosis; renal artery stenosis in a solitary kidney; post-renal transplant patients, presence of only one functioning kidney.

12. Congestive heart failure (NYHA functional class CHF III-IV refer to Appendix 11. 1).

13. Unstable angina within the past three months.

14. Stroke within the past six months.

15. Myocardial infarction or cardiac surgery within the past three months.

16. PTCA within the past three months.

17. Patients who have previously experienced symptoms characteristic of angiodema during treatment with ACE inhibitor or angiotensin II receptor antagonists.

18. Sustained ventricular tachycardia, atrial fibrillation, atrial flutter or other clinically relevant cardiac arrhythmias as determined by the investigator.

19. Hypertrophic obstructive cardiomyopathy, aortic stenosis, hemodynamically relevant stenosis of the aortic or mitral valve.

What this study is about