ranitidine is a medicine that reduces the amount of acid in the stomach it is used to treat and prevent heartburn also known as reflux and ulcers it is also used to prevent damage to the stomach from certain medicines and diseasesranitidine comes in tablet liquid and injection formsyou may also hear ranitidine called by its brand name zantact is also used to prevent damage to the stomach from certain medicines and diseases ranitidine comes in tablet liquid and injection forms you may also hear ranitidine called by its brand name zantac