Efficacy and Safety of Olmesartan Associated With Chlorthalidone in Essential Arterial Hypertension Control

Inclusion Criteria: * Signed Consent of the patient; * Participants with decompensated essential hypertension, classified into stage 1 (with high or very high cardiovascular risk), stage 2 or stage 3 according to the Brazilian Society of Cardiology (2010), who have never been treated and have indication for drug combination treatment. Obs: The diagnosis may be established by previous evaluation of two blood pressure measures ≥ 140/90 mmHg, with two months difference between measurements Exclusion Criteria: * Patients with any clinically significant disease that in the investigator is opinion can not participate in the study; * Secondary hypertension diagnosis or blood pressure above 190x100 mmHg in the screening/randomization visit; * Morbid obesity or immunocompromised patients; * Participants with greater than 10 mmHg difference in the measurements of systolic or diastolic blood pressure between the two arms; * Participants who do not have the two upper limbs; * Participants with important electrocardiographic changes; * Creatinine clearance - less than 60 mL /min; * History of hypertensive emergencies and cardiovascular and / or moderate to severe cerebrovascular events in the past 6 months; * Microalbuminuria in urine sample greater than 30 mg/g; * Patients with history of hypersensitivity to any of the formula compounds; * Pregnancy or risk of pregnancy and lactating patients; * Participation in clinical trial in the year prior to this study.