Drug interactions
Cimetidine + Diltiazem
Severity: Moderate
Cimetidine and Diltiazem: 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 increases diltiazem exposure, which can enhance its effects on heart rate, atrioventricular conduction and blood pressure. Bradycardia, hypotension or conduction block may occur in susceptible patients.
What this interaction means in plain words
Cimetidine and Diltiazem 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; Diltiazem belongs to Cardiovascular.
Why it happens
Cimetidine inhibits CYP3A4 metabolism of diltiazem and may also reduce its tubular secretion.
What to do
Monitor heart rate, blood pressure and ECG when starting or stopping cimetidine, and reduce the diltiazem dose if needed. Consider famotidine as an alternative.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Cimetidine and Diltiazem, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
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 Diltiazem
- Diltiazem + Flibanserin Contraindicated
- Diltiazem + Ivabradine Contraindicated
- Diltiazem + Lomitapide Contraindicated
- Diltiazem + Lonafarnib Contraindicated
- Acebutolol + Diltiazem Major
- Alfentanil + Diltiazem Major
Frequently asked questions
Can I take Cimetidine with Diltiazem?
MediHelp rates the interaction as moderate. Cimetidine and Diltiazem 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 increases diltiazem exposure, which can enhance its effects on heart rate, atrioventricular conduction and blood pressure. Bradycardia, hypotension or conduction block may occur in susceptible patients.
How serious is the interaction between Cimetidine and Diltiazem?
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 heart rate, blood pressure and ECG when starting or stopping cimetidine, and reduce the diltiazem dose if needed. Consider famotidine as an alternative.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
