Noun | 1. | famotidine - a histamine blocker (trade name Pepcid) used to treat peptic ulcers and gastritis and esophageal reflux histamine blocker - a medicine used to treat the gastric effects of histamine in cases of peptic ulcers and gastritis and gastroesophageal reflux; works by blocking the effects of histamine on the receptor site known as H2 |