This study was conducted to compare the rate and extent of absorption of valsartan and hydrochlorothiazide. To maximize the possibility of finding drug-drug interactions, the dose of valsartan and hydrochlorothiazide was doubled (320 mg of VAL and 25 mg of HCT).

Inclusion Criteria:

• At least 18 years old and not more than 45 healthy male volunteers
• Actual weight no more than ± 30% from ideal body weight based on sex, height, and body frame
• Who had passed all the screening parameters
• Free of any drug exposure known to interfere with the pharmacokinetics or assay of fexofenadine for at least 10 days prior to the study
• Who had to be able to communicate effectively with study personnel, be literate, and able to give consent.

Exclusion Criteria:

• A clinically significant abnormal physical exam, medical history, or laboratory studies
• If they showed a sitting SBP of >140 or <100 mmHg, DBP > 90 or <60mm Hg, or a pulse rate of > 95 or < 50 beats/min at screening
• A history of serious intolerance, allergy, or sensitivity to fexofenadine
• The use of any prescription drug within the previous month or use of any over-the-counter medication (with the exception of acetaminophen) within the past 14 days
• A history of blood dyscrasias
• A history of alcohol or drug abuse within the past year
• Donation of blood during the 8 weeks prior to the study or plans to donate blood during or within 8 weeks of completing the study
• Unable to tolerate vein puncture and multiple blood samplings
• Any surgical/medical condition that might alter drug absorption, distribution, metabolism, or excretion
• Cannot follow instructions, in the opinion of the investigator.