Inclusion Criteria:

1. patients aged at least 18 years at the date of signing the consent form
2. diagnosis of essential hypertension and blood pressure not adequately controlled before enrolment in the study
3. failure to respond adequately to six weeks treatment with amlodipine 5 mg monotherapy
4. able to stop any current antihypertensive therapy without unacceptable risk to the patient (Investigator's decision)
5. willing and able to provide written informed consent (in accordance with Good Clinical Practice and local legislation).

Exclusion Criteria:

1. are not practising acceptable means of birth control or do not plan to continue using acceptable means of birth control throughout the study and do not agree to submit to pregnancy testing during participation in the trial. Acceptable methods of birth control include the transdermal patch, oral, implantable or injectable contraceptives, sexual abstinence and vasectomised partner.
2. known or suspected secondary hypertension
3. mean seated SBP over 200 mmHg and/or mean seated DBP over 120 mmHg at Visit 1 or 2 or mean seated SBP over 180 mmHg and/or mean seated DBP over 120 mmHg at the end of the run-in period (Visit 3)
4. any clinically significant hepatic impairment (e.g. clinically significant cholestasis, biliary obstructive disorder or hepatic insufficiency)
5. severe renal impairment (e.g. serum creatinine >3.0 mg/dL or >265 mcmol/L, known creatinine clearance <30mL/min or clinical markers of severe renal impairment)
6. bilateral renal artery stenosis or renal artery stenosis in a solitary kidney or post-renal transplant
7. clinically relevant hyperkalaemia
8. uncorrected volume or sodium depletion.
9. primary aldosteronism.
10. hereditary fructose or lactose intolerance