Isolated Systolic Hypertension (ISH)is the dominating hypertensive disease in elderly people. Much attention has recently been drawn to the strong relationship between the systolic blood pressure and cardiovascular morbidity.

In previous clinical studies carried out in individuals with normal blood pressure at baseline SER100 decreased primarily the systolic blood pressure. It is hypothesized that the effect on systolic blood pressure in hypertensive patients will be larger or equal to the fall seen in normotensive patients.

Inclusion Criteria:

• Mean systolic blood pressure ≥ 150 mmHg and mean diastolic blood pressure < 90 mmHg - as determined by daytime continuous ambulatory blood pressure measurement (ABPM)
• Male or female
• Age 50-80 years (both inclusive) at screening
• Patients must be on stable doses with one or more antihypertensives
• BMI <32 kg/m2
• Written informed consent

Exclusion Criteria:

• Acute myocardial infarction in the last 6 months before screening
• Stroke in the last 6 months before screening
• Uncompensated heart failure (NYHA Class IV)
• Angina pectoris with an anticipated need for administration of short-acting nitrates
• Known, severe sleep apnoea
• Abnormal laboratory values (i.e. > 2 x upper normal limit) at screening
• Subjects working night shifts (11 PM to 7 AM)
• Participation in any other clinical trial with an investigational medicinal product or device within 1 month prior to randomisation.
• Subjects with upper arm circumference ≤24 cm or ≥ 42 cm.
• Any general condition, serious disease or current evidence of any mental or physical disorder or collaboration attitude (e.g. dementia, substance abuse) which, in the judgment of the investigator makes the subject unsuitable for enrollment, and/or may interfere with the study evaluations or affect subject's safety and/or may cause risk for poor protocol compliance
• Pregnant or lactating women.
• Female subjects of childbearing potential, or male subjects whose female partner (unless post-menopausal for 1 year or surgically sterile) is unwilling to use adequate contraceptive measures throughout the duration of the study