Q. A 55-year-old man with a 5-year history of burning in the chest, chronic sore throat and a metallic taste, as well as chronic cough, and wheezes comes to the emergency department because of a dysphagia sensation. An upper endoscopy and biopsy of the distal esophagus are done, the biopsy shows simple columnar epithelium with glandular cells. He has no significant past medical history except for hypertension, which is now controlled with diet and exercise. Temperature is 36.7 (98.7 F), Blood Pressure is 140/80, Heart Rate is 68 beats/minute. Cardiopulmonary auscultation is normal. No masses present on abdominal examination. You diagnose him with gastroesophageal reflux disease. You want to start him on a medication to treat his GERD but you have to warn him that unfortunately, it can increase the risk for osteoporosis and clostridium difficile infection. What is the mechanism of this class of medication?