Azilsartan Circadian and Sleep Pressure

To determine the efficacy of Azilsartan 20 mg versus Amlodipine 5 mg oral administration once per day for 8 weeks in patients with grade I or grade II essential hypertension.

Treatment

\<Run-in period\> Use of any antihypertensives, including azilsartan and amlodipine, is prohibited during the run-in period.

\<Treatment period\> Subjects who are considered eligible for participation in the study based on the results of eligibility assessment during the run-in period will be randomized to the azilsartan 20 mg or amlodipine 5 mg group at a ratio of 1:1 according to the following stratification factors; the type of awake-sleep blood pressure variation determined based on the data from ABPM at the start of run-in, complication status (chronic kidney diseases \[CKD\], type 2 diabetes), age, and sex.

Subjects will start treatment with either antihypertensive after examination for the start of treatment (Week 0) and visit the study site every 2 weeks, 5 visits in total, until the end of treatment (Week 8).

Subjects will orally take azilsartan 20 mg or amlodipine 5 mg, according to their group allocation, once daily before or after breakfast in the morning.

Eligibility Criteria:
Inclusion Criteria:

* Grade I or II essential hypertension
* The sitting systolic blood pressure is in term of 140-179 mmHg, or sitting diastolic blood pressure is in term of 90-109 mmHg at the both two time points at the beginning of the observation period and at the beginning of a treatment period (Week0)
* 20 years old or older at the time of the informed consent
* Able to give written informed consent before participating in the research
* Therapeutic category during the observation period: Ambulatory

Exclusion Criteria:

* Secondary hypertension, grade III hypertension (sitting systolic blood pressure greater than or equal to 180 mmHg or sitting diastolic blood pressure greater than or equal to 110 mmHg), malignant hypertension
* More than 2 kinds of antihypertensive agents for treatment on the hypertension
* History of taking following medicines within 2 weeks before start of the observation period.

When subject with taking any of the following medicine at the time of informed consent is included, stop to take the medicine for determined period after the informed consent.

I. Antihypertensive agents II. Antianginal agents III. Antiarrhythmic agents (except single time use of the lidocaine hydrochloride formulation for anesthesia) IV. Digitalis products

* Less than 130 mmHg of mean 24-hour systolic blood pressure and less than 80 mmHg of mean 24-hour diastolic blood pressure at the start of the observation period.
* History of following circulatory-related diseases or symptoms within 24 weeks before start of the observation period.

I. Cardiac disease: Myocardial infarction, coronary artery revascularization II. Cerebrovascular-disease: cerebral infarction, cerebral hemorrhage, transient ischemic attack III. Progressive hypertensive retinopathy: hemorrhage, exudation, or papilledema

* History or complication with the following circulatory-related diseases; Valvular stenosis, atrial fibrillation, pharmacotherapy-required angina, congestion heart failure, or cardiac arrhythmia, or arteriosclerosis obliterans with symptoms of intermittent claudication et al
* Day / night reversal
* History of hypersensitivity or allergy to Azilsartan, Amlodipine, or related drugs
* Participant in any other clinical research
* Pregnant, possible to being pregnant, or lactating woman
* Mal-control of blood pressure during informed consent to taking antihypertensive agent
* Any those the investigator or other researchers consider as unsuitable