This study was planned to assess the concentration of antihypertensive drugs in the blood plasma in patients with controlled and uncontrolled arterial hypertension. Methods: it is planned to include patients with arterial hypertension taking 3 antihypertensive drugs (indapanide, lisinopril or valsartan, amlodipine). Based on the results of 24-hour blood pressure monitoring, the patients will be randomized into two groups: The first group - the patients with controlled AH; The second group - the patients with uncontrolled AH. Venous blood was taken in both groups of the patients in the morning before and 2 hours after taking drugs to assess the concentration of lisinopril, amlodipine, valsartan and indapamide. Concentation of assesed antihypertensive drugs will be compared in both groups.

Inclusion Criteria:

• Signed informed consent form;
• An established diagnosis of AH based on the Clinical Guidelines "Arterial hyperten-sion in adults", approved by the Scientific and Practical Council of the Ministry of Health of the Russian Federation, 2020;
• Mandatory patient compliance with recommendations for lifestyle modification in accordance with the Clinical Guidelines "Arterial hypertension in adults", approved by the Scientific and Practical Council of the Ministry of Health of the Russian Federation, 2020 .
• Regular administration of any two antihypertensive drugs (lisinopril, amlodipine, valsartan) in combination with indapamide for a month, possibly in fixed combinations, in stable dosages;
• Fertile female patients must use proper methods of contraception throughout the study period.

Exclusion Criteria:

• Patient's connection with the organization or conducting of the study;
• Pregnancy.