Effects of Gastric pH on the Pharmacokinetics of Atazanavir

Inclusion Criteria: * Male or female 18-65 years of age * Healthy adult with no active medical problems or significant chronic diseases as determined by the study doctor based on history, physical exam and laboratory evaluations * BMI between 18.5-30 kg/m2 * Taking no medications 2 weeks before and during the study enrollment, including drugs of abuse, prescription or over-the-counter (OTC) medications (except acetaminophen) * Subjects able to maintain adequate birth control during the study independent of hormonal contraceptive use * Be able to provide written informed consent and comply with requirements of the study * Avoid eating grapefruit and drinking grapefruit juice from 7 days before the first study day until the completion of the entire study * Abstinence from alcoholic beverages, caffeinated beverages and orange juice from 3pm the night before a study day until completion of that study day * Fast from food and beverages at least 8 hours prior to medication dosing * Be able to read, speak, and understand English Exclusion Criteria: * Subjects with a history of gastrointestinal disease including gastroesophageal reflux disease, gastritis, peptic ulcer disease, or dyspepsia * Subjects with a fasting gastric pH of \> 4 (i.e. hypochlorhydria) * Subjects with a history of dysphagia, achalasia, or difficulty swallowing capsules, tablets, or pills * Subjects on prescription or chronic over-the-counter (OTC) medications (including hormonal contraceptives) * Subjects with known allergies rabeprazole, any other proton pump inhibitors (PPI's) or betaine hydrochloride * Subjects who smoke tobacco * Subjects with ongoing alcohol or illegal drug use * Subjects who are pregnant, lactating, or attempting to conceive * Subjects unable to maintain adequate birth control during the study