Compare Efficacy and Safety of Telmisartan/Hydrochlorothiazide With Telmisartan/Hydrochlorothiazide Plus Amlodipine

This is a multi-centre, randomised, double-blind, active-controlled, parallel-group comparative trial to compare the fixed dose combination (FDC) of telmisartan 80 mg + hydrochlorothiazide 12.5 mg and amlodipine 5 mg (T80/A5/H12.5 mg) to telmisartan 80 mg+ hydrochlorothiazide 12.5 mg (T80/H12.5 mg) in blood pressure lowering effect at week 8, the end of the double-blind period in essential hypertensive patients who fail to respond adequately to telmisartan 80 mg+ hydrochlorothiazide 12.5 mg. Patients are assigned to one of the two groups after a 6-week open-label run-in period taking T80/H12.5 mg. In addition the long-term safety of telmisartan 80 mg+ amlodipine 5 mg+ hydrochlorothiazide 12.5 mg will be evaluated in a 52-week extension period. In the 52-week open label extension period patients who are assigned to the T80/A5/H12.5 mg group continue the T80/A5/H12.5 mg therapy, and patients who are assigned to the T80/ /H12.5 mg group change to the T80/A5/H12.5 mg therapy.