Zantac pills used to treat duodenal and peptic ulcers as well as chronic dyspepsia (indigestion). They are resting on a sheet that informs the patient of the possible side effects of taking the drug. Zantac contains the active ingredient ranitidine hydrochloride. It works by inhibiting the production of gastric acid. Zantac is produced by the GlaxoSmithKline company.