Effects of Combination Therapy With Alpha-1 Blocker (Bunazosin or Doxazosin) in the Treatment of Patients With Mild to Moderate Essential Hypertension

Inclusion Criteria: Subjects with mild to moderate essential hypertension, with the following criteria: Washout period (Week -2) Male or female subjects aged 20 to 80 years Systolic blood pressure (SBP):140 mm Hg but <180 mm Hg and/or diastolic blood pressure (DBP):90 mm Hg but <110 mm Hg Subjects who have given written informed consent prior to participation in the trial and who undertake to comply with the protocol Angiotensin II antagonist mono-therapy period (week 0) Subjects with systolic blood pressure >= 140 mm Hg but <180 mm Hg and/or diastolic blood pressure >= 90 mm Hg but <110 mm Hg Presence of any 2 of the following 4 risk factors Waist circumference: male > 90 cm, female > 80 cm Triglycerides >= 150 mg/dl HDL cholesterol: male < 40 mg/dl, female < 50 mg/dl Fasting glucose >= 110 mg/dl Angiotensin II antagonist with add-on Bunazosin or Doxazosin treatment period (Week 5) SBP >=140 mm Hg or decrease < 10 % OR DBP >=90 mm Hg or decrease < 10 % comparing the blood pressure at the entry of the Angiotensin II antagonist mono-therapy period. Exclusion Criteria: Subjects with the following conditions are not eligible for participation： a) Washout period (Week -1 or -2) Subjects with severe hypertension (SBP>=180 mm Hg or DBP>=110 mm Hg). Subjects who have proven or suspected hypersensitivity to quinazoline derivatives Subjects who have a history of alcohol or drug abuse. Subjects with past or present evidence of cancer Subjects who have a past history of arterial fibrillation, heart failure (LVEF<40%), acute coronary syndrome, myocardial infarction, stroke or severe arrhythmia. Subjects who are severely obese (BMI>30 kg/m2) Women who are pregnant or lactating or suspected of being pregnant. Subjects who have previously participated in any clinical trial of new or unapproved substances within the 12 weeks before starting of washout period Subjects on other anti-hypertensive or lipid-lowering medication Inability to return for scheduled visits or comply with any other aspect of the Protocol Subjects with poorly controlled diabetes mellitus (HbA1c > 10%) Subjects with concurrent serious hepatic or renal disorders (defined as AST and/or ALT > 3 times upper normal limit or Cr > 2mg/dl). Subjects who, in the opinion of the investigators, are poor medical candidates or pose any other risk for therapy with an investigational drug.