Can famotidine (histamine-2 (H2) blocker) cause diarrhea?

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Last updated: June 29, 2025View editorial policy

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From the Research

Famotidine can cause diarrhea as a side effect, occurring in approximately 1-2% of patients taking this H2 blocker medication. While most people tolerate famotidine well, gastrointestinal disturbances including diarrhea, constipation, and abdominal discomfort are among the more common adverse effects 1. The mechanism behind famotidine-induced diarrhea likely relates to its effects on histamine receptors in the digestive tract, which can alter gastric acid secretion and potentially impact gut motility and the intestinal microbiome.

Some key points to consider:

  • Diarrhea is a known side effect of famotidine, as reported in studies such as the one published in 2002 1, where diarrhea was noted in 4 out of the patients treated with famotidine.
  • The incidence of diarrhea with famotidine is relatively low, but it is essential for patients to be aware of this potential side effect and to consult their healthcare provider if they experience persistent or severe diarrhea.
  • If you experience persistent or severe diarrhea while taking famotidine, you should consult your healthcare provider, as they may recommend reducing the dose, switching to a different H2 blocker or acid-reducing medication, or discontinuing the medication if the side effect is troublesome 1.
  • Most cases of famotidine-induced diarrhea resolve once the medication is stopped, and it's crucial to stay hydrated if you experience this side effect and to report any signs of dehydration or bloody stools to your doctor immediately.

It's also worth noting that famotidine has been shown to be effective in relieving abdominal symptoms and improving quality of life in patients with chronic symptomatic gastritis, as demonstrated in a study published in 2012 2. However, the primary concern in the context of this question is the potential for famotidine to cause diarrhea, and patients should be aware of this possible side effect when taking the medication.

References

Research

[Efficacy of gastrosidine (famotidine) in the treatment of gastroesophageal reflux at the reflux esophagitis stage].

Eksperimental'naia i klinicheskaia gastroenterologiia = Experimental & clinical gastroenterology, 2002

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