The purpose of this study is to evaluate the blood pressure lowering effects of an amlodipine/losartan combination treatment and losartan/Hydrochlorothiazide combination treatment in patients with essential hypertension uncontrolled with losartan 100mg monotherapy.

• Quality assurance plan was implemented by site monitoring, including data validation and registry procedures and Source data verification to assess the accuracy, completeness by comparing the data to external data sources (medical records and paper case report forms).
• Data dictionary contains the registry, including the source of the variable, coding information (MedDRA ver12.0), and normal ranges.
• Statistical analysis were performed using SAS® Version 9.2, SAS institute, Cary, NC, USA

Inclusion Criteria:

• 20 aged or over
• Patients with blood pressure measured at Visit 1; 90mmHg≤MSDBP mmHg if on anti-hypertensive drugs, 95mmHg≤MSDBP mmHg if not on anti-hypertensive drugs
• Patients with blood pressure measured at Visit 2 were 90mmHg≤MSDBP mmHg (non-responder to Losartan 100mg for 4-week treatment)

Exclusion Criteria:

• Patients with too high Blood pressure

  •≥ sitSBP 20mmHg or ≥ sitDBP 10mmHg of variation in three measurements from the reference arm selected at Screening

• History of hypersensitivity to CCB ,Angiotensin II receptor blockers or Sulfonamide.

• Secondary hypertension or suspected to be