Efficacy/Safety of Amlodipine Plus Losartan Versus Amlodipine in Patients With Essential Hypertension

Inclusion Criteria: * Patients over 18 years of age * Essential hypertensive patients whose blood pressure is not controlled before the study (sit DBP ≥ 90 mmHg for drug-treated patient, sit DBP ≥ 95 mmHg for drug-naïve patient) * Non-responder to 4 weeks treatment of amlodipine 5 mg monotherapy (sit DBP ≥ 90mmHg) Exclusion Criteria: * mean sit SBP ≥ 200 mmHg or mean sit DBP ≥ 120 mmHg at screening * mean sit SBP ≥ 180 mmHg or mean sit DBP ≥ 120 mmHg after 4 weeks of amlodipine 5 mg treatment * has a history of hypersensitivity to dihydropyridines or angiotensin II receptor blockers * Secondary hypertensive patient or suspected to be * Uncontrolled diabetes mellitus patients * Severe heart disease or severe neurovascular disease * Known as severe or malignant retinopathy * Patients showed clinically significant hematological finding, patients with renal diseases (serum creatinine), patients with hepatic disease (ALT or AST) * History of malignancy tumor * History of autoimmune disease * History of alcohol or drug abuse * Positive to pregnancy test, nursing mother, has an intention on pregnancy * Considered by investigator as not appropriate to participate in the clinical study with othe reason