Ranitidine Hydrochloride Indications Antac is indicated in: Pharmacology Ranitidine competitively blocks histamine at H2-receptors of the gastric parietal cells which inhibits gastric acid secretion. It does not affect pepsin secretion, pentagastrin-stimulated intrinsic factor secretion or serum gastrin. Dosage & Administration Ranitidine Tablet & Syrup: Duodenal and gastric ulcer: The usual dosage is 150 mg twice […]