Drug interactions
Cimetidine + Diphenoxylate
Severity: Moderate
Cimetidine and Diphenoxylate: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Cimetidine may increase diphenoxylate exposure by reducing its hepatic metabolism. This could amplify opioid effects including sedation and respiratory depression, particularly in children or at high doses.
What this interaction means in plain words
Cimetidine and Diphenoxylate can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Cimetidine belongs to Gastrointestinal Tract; Diphenoxylate belongs to Gastrointestinal Tract.
Why it happens
Cimetidine inhibits CYP enzymes, likely including CYP3A4, which metabolize diphenoxylate.
What to do
Monitor for oversedation, anticholinergic effects and respiratory depression, and keep diphenoxylate doses low. Use famotidine as an alternative acid suppressant if needed.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Cimetidine
- Cimetidine + Dofetilide Contraindicated
- Cimetidine + Fezolinetant Contraindicated
- Alfentanil + Cimetidine Major
- Atazanavir + Cimetidine Major
- Carmustine + Cimetidine Major
- Cimetidine + Citalopram Major
Other interactions of Diphenoxylate
Frequently asked questions
Can I take Cimetidine with Diphenoxylate?
MediHelp rates the interaction as moderate. Cimetidine and Diphenoxylate can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Cimetidine may increase diphenoxylate exposure by reducing its hepatic metabolism. This could amplify opioid effects including sedation and respiratory depression, particularly in children or at high doses.
How serious is the interaction between Cimetidine and Diphenoxylate?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for oversedation, anticholinergic effects and respiratory depression, and keep diphenoxylate doses low. Use famotidine as an alternative acid suppressant if needed.
What other medicines interact with Cimetidine?
MediHelp also lists interactions of Cimetidine with, for example, Dofetilide, Fezolinetant, Alfentanil. The full list is on the Cimetidine page.
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