Efficacy/Safety of Amlodipine Plus Losartan Versus Losartan 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≥95mmHg for drug-naïve patient) * Non-responder to 4 weeks treatment of losartan 100 mg monotherapy (sit DBP≥90mmHg) Exclusion Criteria: * mean sit SBP≥200mmHg or mean sit DBP≥120mmHg at screening * mean sit SBP≥180 mmHg or mean sit DBP≥120mmHg after 4 weeks of losartan 100mg 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