Introduction Other agents: cimetidine, famotidine, and nizatidine Mechanism indirectly inhibit proton pump by blocking stimulation via H2 receptors on parietal cells and ECL cells leads to ↓ H+ secretion by parietal cells no effect on gastic emptying time Clinical use peptic ulcer gastritis GERD Zollinger-Ellison syndrome Toxicity cimetidine potent inhibitor of P-450 antiandrogenic effects login to view 1 more bullet crosses blood-brain barrier login to view 2 more bullets crosses placenta cimetidine and rantidine ↓ creatinine clearance other H2 blockers have fewer side effects