Famotidine-Associated Diarrhea

Mechanism and Incidence

Famotidine is a histamine H2-receptor antagonist that works by inhibiting gastric acid secretion, and it is considered to have a favorable safety profile compared to other acid-reducing medications, with a relatively low incidence of diarrhea as a side effect 1
Unlike proton pump inhibitors, famotidine is metabolized differently and does not significantly interact with the cytochrome P-450 system, particularly CYP2C19, which may contribute to its lower incidence of diarrhea 2

Clinical guidelines mention diarrhea as a potential side effect of famotidine, though it is not among the most commonly reported adverse effects, with the American College of Cardiology noting its relatively favorable side effect profile 1
In specific patient populations, famotidine is sometimes used therapeutically to help manage certain types of chronic diarrhea, with a strength of evidence suggesting its potential benefits in these cases 3
The American Heart Association suggests that H2 blockers like famotidine may be considered as alternatives to PPIs for patients on antiplatelet therapy, due to their generally favorable side effect profile, including a lower incidence of diarrhea 5, 4

If diarrhea develops while taking famotidine, the American College of Gastroenterology recommends evaluating for other causes of diarrhea, potentially reducing the dose if symptoms are mild, switching to another H2 blocker or different class of acid-reducing medication if symptoms persist, and ensuring adequate hydration to prevent dehydration 3, 1, 2