Drug interactions
Cimetidine + Fentanyl
Severity: Moderate
Cimetidine and Fentanyl: 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 can reduce CYP3A4 clearance of fentanyl and raise its concentrations, intensifying sedation and respiratory depression. The risk is more relevant with continuous or transdermal fentanyl.
What this interaction means in plain words
Cimetidine and Fentanyl 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; Fentanyl belongs to Musculoskeletal.
Why it happens
Cimetidine inhibits CYP3A4, reducing fentanyl metabolism.
What to do
Monitor for sedation and respiratory depression and adjust fentanyl dose; consider famotidine as the acid suppressant.
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 Fentanyl
- Alvimopan + Fentanyl Contraindicated
- Fentanyl + Isocarboxazid Contraindicated
- Fentanyl + Olanzapine / samidorphan Contraindicated
- Fentanyl + Phenelzine Contraindicated
- Fentanyl + Tranylcypromine Contraindicated
- Alfentanil + Fentanyl Major
Frequently asked questions
Can I take Cimetidine with Fentanyl?
MediHelp rates the interaction as moderate. Cimetidine and Fentanyl 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 can reduce CYP3A4 clearance of fentanyl and raise its concentrations, intensifying sedation and respiratory depression. The risk is more relevant with continuous or transdermal fentanyl.
How serious is the interaction between Cimetidine and Fentanyl?
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 sedation and respiratory depression and adjust fentanyl dose; consider famotidine as the acid suppressant.
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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