Kirkland Signature Acid Controller is an H2 Blocker and Histamine Receptor Antagonist. These partially block production of acid in the stomach cells by inhibiting histamine, a substance that stimulates secretion of stomach acid. Over-the-counter and prescription H2 blockers relieve heartburn associated with acid indigestion and sour stomach and prevent meal-induced heartburn. These acid reducers generally relieve symptoms for a longer period of time than antacids, but take time to work initially. Over-the-counter H2 blockers include Ranitidine and Famotidine. Prescription H2 blockers may provide short-term treatment of symptomatic gastroesophageal reflux disease (GERD) and, with longer duration and higher daily dosages, relief of erosive esophagitis.