Rabeprazole is a new proton pump inhibitor (PPI) with potent anti-secretion action and dose-dependence activity. Rabeprazole is rapidly eliminated by hepatic metabolism and renal clearance. In previous studies in healthy volunteers, interactions between sodium rabeprazole and drugs such as warfarin, theophyline, diazepam and phenytoin have not been found. The objective of the study is to evaluate the safety of rabeprazole as concomitant treatment and examine the clinical practice of the interaction with drugs whose absorption has a gastric pH dependence. This is an observational, multicenter, open and prospective study. It is expected to enroll 500 patients receiving rabeprazole and a concomitant drug (one or more). All data collected will be prospective and will include the following: demographic data, adherence and compliance with treatment, lifestyle (smoking and alcohol consumption) and dose of rabeprazole. Safety analysis will be based on adverse events. Observational Study: For patients with duodenal or gastric ulcer: rabeprazole 20mg per day, orally, for 4-6 weeks; For patients with erosive or ulcerate gastroesophagic reflux: rabeprazole orally 20mg/ per day, 4-8 weeks; For patients with gastroesophagic reflux requiring prolonged treatment: rabeprazole orally 10 or 20 mg per day; For patients with H. Pylori: rabeprazole orally 20mg twice per day , Clarithromycin orally 500mg 2 times per day and Amoxicillin 1gram orally twice daily for 1 week.