The purpose of this study is to evaluate the safety of rabeprazole 20mg/day in polymedicated patients and to examine the necessity of adjusted dosage in both therapies (rabeprazole and concomitant drug). Proton pump inhibitors (PPI) act in the final step of the gastric secretion. PPI's block ATP-ase H+/K+ in gastric parietals cells. It has been described that inhibition of acid secretion has produced the recovery of the gastroesophageal pathology in a high percentage of the patients resistant to conventional drugs. In this context, the objective of the study is to evaluate the safety of rabeprazole as a concomitant treatment and examine the clinical practice the interaction with drugs whose absorption has gastric pH dependence.