The present invention refers to new oral pharmaceutical, nutraceutical, health foods and medical device compositions based on polysaccharides from Opuntia Ficus Indica cladodes in fixed or therapeutic combination with other actives and/or with other substances useful for the prevention or the of treatment of GERD (Gastro-Esophageal Reflux Disease), gastric esophagitis and related diseases (e.g. dyspepsia, esophagitis, esofageal tumour, gastrointestinal symptoms, chronic pharyngitis, Barrett's esophagus, esophageal adenocarcinoma, GERD-related pulmonary symptoms). Said compositions, which have synergic action with substances useful for the treatment of the same diseases, allow to reduce the effective dose improving its therapeutic index.