Snapshot A 50-year-old man presents to his primary care physician for his annual examination. He has a history of hypertension, managed with lifestyle modification but is otherwise healthy and not taking any medication. He reports that his only concern today is that he develops some acid reflux after eating heavy or spicy foods. This occurs especially after he lies down after a big meal. He is instructed to use an over-the-counter antacid, such as calcium carbonate, as needed. Introduction Drugs aluminum hydroxide calcium carbonate magnesium hydroxide Mechanism of action neutralizes acid in the stomach delays gastric emptying Antacids Aluminum Hydroxide Calcium Carbonate Magnesium Hydroxide Mechanism of Action Neutralizes acid in the stomach Delays gastric emptying Acts as a phosphate binder Neutralizes acid in the stomach Delays gastric emptying Acts as a phosphate binder Neutralizes acid in the stomach Delays gastric emptying Promotes osmotic retention of fluid and induces diarrhea Clinical Use of All Antacids Acid reflux Peptic ulcer disease Aluminum hydroxide Other Clinical Uses Hyperphosphatemia Calcium supplementation Constipation Adverse effects Constipation Decreased phosphate: muscle weakness osteodystrophy Milk-alkali syndrome: ↑ calciumin severe cases, can cause metastatic calcification and renal failure Can chelate and decrease the efficacy of some drugs, particularly tetracyclines (doxycycline, tetracycline, and minocycline) Diarrhea Hypotension Cardiac arrest