The goal of this study is to evaluate the ability of a natural supplement (betaine hydrochloride) to affect the absorption of atazanavir in healthy volunteers. The investigators predict that betaine hydrochloride will increase the absorption of atazanavir in volunteers pre-treated with proton-pump inhibitors (PPIs).

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