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 diseases.Ranitidine comes in tablet, liquid, and injection forms.You may also hear ranitidine called by its brand name, Zantac®.t 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 diseases. Ranitidine comes in tablet, liquid, and injection forms.