Zantac is a brand name for Ranitidine, which belongs to a class of drugs called H2 blockers. H2 blockers reduce the amount of acid produced in the stomach and are commonly used to treat conditions like heartburn and ulcers, which are often managed with antacids or acid-reducing medications. The other options (Cetirizine, Iproniazid, Chlorpheniramine) are not primarily used for stomach acid problems.