The purpose of this clinical research is to learn if moderate hypertension can be better controlled by initially treating with a combination of drugs (Irbesartan/HCTZ), in patients who are unlikely to achieve blood pressure (B/P) control with only one drug. In addition, the study will also evaluate the safety and tolerability of the drugs.

Inclusion Criteria:

• Willing to provide written informed consent

• Subjects must have uncontrolled hypertension defined as:

  • average systolic blood pressure between 160 mmHg and 180 mmHg (while diastolic blood pressure is less than 110 mmHg) or
  • average diastolic blood pressure between 100 mmHg and 110 mmHg (while systolic blood pressure is between 130 mmHg and 180 mmHg)

• Subjects must be willing to discontinue their antihypertensive medication, if applicable.

• Men and women, ages 18 and older will be included.

• Women of childbearing potential (WOCBP) must be using an adequate method of contraception to avoid pregnancy throughout the study and for up to one week after the study in such a manner that the risk of pregnancy is minimized. WOCBP must have a negative serum or urine pregnancy test within 72 hours prior to the start of study medication.

Exclusion Criteria:

• Women who are pregnant or breastfeeding
• Known or suspected secondary hypertension
• Hypertension emergencies or stroke within the past 12 months.
• Heart attack, angina or bypass surgery within the past six months.
• Significant kidney disease
• Significant liver disease
• Systemic lupus erythematosus
• Gastrointestinal disease or surgery that interfere with drug absorption
• Cancer during the past five years excluding localized squamous cell or basal cell carcinoma of the skin
• Currently pregnant or lactating
• Mental condition (psychiatric or organic cerebral disease) rendering the subject unable to understand the nature, scope, and possible consequences of the study
• Drug or alcohol abuse within the last five years
• Known allergy to irbesartan or diuretics