Skilled nurse instructed patient about medication Famotidine is used to treat ulcers (sores on the lining of the stomach or small intestine); gastroesophageal reflux disease (GERD, a condition in which backward flow of acid from the stomach causes heartburn and injury of the esophagus [tube that connects the mouth and stomach. Shake the liquid well for 5 to 10 seconds before each use to mix the medicine evenly. Swallow the tablets and capsules with a full glass of water.The following symptoms are common, but if you experience any of them call your doctor immediately: hives, skin rash, itching, swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs.