Can you take Pepcid (Famotidine) when checking for Helicobacter pylori (H. pylori)?

Taking Famotidine When Testing for H. pylori

Famotidine (Pepcid) should be stopped for at least 2 weeks before H. pylori testing when using culture, histology, rapid urease test, urea breath test (UBT), or stool antigen test, as it can lead to false-negative results. 1

Effect of Famotidine on H. pylori Testing

Impact on Test Accuracy

• H2-receptor antagonists like famotidine can cause false-negative results in H. pylori diagnostic tests, though to a lesser extent than proton pump inhibitors (PPIs) 1
• By increasing gastric pH, famotidine leads to local changes in the stomach that decrease the bacterial load, especially in the antrum 1
• This reduction in bacterial load can result in false-negative results for most diagnostic tests 1

Different Tests and Their Susceptibility to Interference

• Tests affected by famotidine use:

  • Urea breath test (UBT): Can show 10-40% false-negative results 1
  • Stool antigen test (SAT): Similar false-negative rates as UBT 1
  • Biopsy-based tests: Including culture, rapid urease test, and histology 1

• Test not affected by famotidine:

  • Serology (IgG antibody testing): The only test not affected by antisecretory drugs 1
  • H. pylori antibodies remain present for months after suppression or even eradication of H. pylori 1

Recommendations for Testing

When to Stop Famotidine

• Stop famotidine at least 2 weeks before testing to allow bacteria to repopulate the stomach 1
• This waiting period allows previously negative tests (UBT, SAT, rapid urease test, histology, culture) to become positive again 1

Alternative Testing Options

• If stopping famotidine is not possible, validated IgG serology can be performed instead 1
• When using the urea breath test with citric acid as the test meal, the panel did not find it necessary to stop H2-receptor antagonists before testing 1, 2

Clinical Considerations

Special Situations

• For patients who cannot stop famotidine due to symptom management needs, serology is the preferred testing method 1
• Only validated commercial serological tests with >90% accuracy should be used 1

Common Pitfalls

• Failing to recognize that H2-receptor antagonists like famotidine can cause false-negative results, though the effect is less pronounced than with PPIs 2
• Not allowing sufficient washout time before testing, which can lead to misdiagnosis and inappropriate management 1
• Using rapid in-office serological tests, which have limited accuracy compared to laboratory ELISA tests 1

By following these evidence-based recommendations, clinicians can avoid false-negative results and ensure accurate diagnosis of H. pylori infection, which is crucial for appropriate patient management and treatment.