• Pharmacokinetic, pharmacodynamic and safety parameters of rabeprazole will be listed and summarized.
  

This is an open-label (both physician and patient know the name of the study medication), multicenter, Phase I study, consisting of 2 parts. The first part of the study will be nonrandomized, all patients will receive the same dose. In the second part of the study, patients will be randomized (study medication assigned by chance) into 2 dose groups. The purpose of the study is to evaluate the pharmacokinetics, pharmacodynamics (intraesophageal/intragastric pH, clinical global impression, formulation palatability and Gastroesophageal Reflux Disease (GERD) daily symptom diary) and safety of rabrepazole after single and multiple daily administration at 2 dose levels in infants between the ages of 1 and 11 months, inclusive (up to 11 months 29 days), with GERD. As this study is an exploratory assessment of the pharmacokinetics, pharmacodynamics and safety of rabeprazole in infants, no formal hypothesis testing is applied. Safety and tolerability, including monitoring of adverse events, clinical laboratory results, physical examination, vital signs and ECG measurements, will be evaluated throughout the study. Patients will receive rabeprazole sodium as single daily oral doses for 5 successive days as a bead formulation. Patients in the first part of the study will receive single and multiple daily every 24 hours doses of 0.14 mg/kg, using increments of 1 mg dose. Safety and pk data from part 1 of the study will determine the 2 dosages to be studied in part 2 of the study.