Drug interactions
Fentanyl transmucosal + Metronidazole
Severity: Moderate
Fentanyl transmucosal and Metronidazole: 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
Fentanyl is cleared mainly by CYP3A4, so any agent that reduces this clearance can raise fentanyl exposure. Metronidazole is only a weak CYP3A4 inhibitor, so the effect is modest, but higher fentanyl levels can cause excess sedation and respiratory depression.
What this interaction means in plain words
Fentanyl transmucosal and Metronidazole 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.
Why it happens
Possible weak inhibition of CYP3A4-mediated fentanyl metabolism by metronidazole.
What to do
Monitor for sedation and respiratory depression, especially when metronidazole is started or stopped. Adjust the fentanyl dose if signs of opioid excess appear.
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 Metronidazole
- Ethanol + Metronidazole Contraindicated
- Metronidazole + Pimozide Contraindicated
- Amiodarone + Metronidazole Major
- Disulfiram + Metronidazole Major
- Ergotamine + Metronidazole Major
- Lomitapide + Metronidazole Major
Frequently asked questions
Can I take Fentanyl transmucosal with Metronidazole?
MediHelp rates the interaction as moderate. Fentanyl transmucosal and Metronidazole 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. Fentanyl is cleared mainly by CYP3A4, so any agent that reduces this clearance can raise fentanyl exposure. Metronidazole is only a weak CYP3A4 inhibitor, so the effect is modest, but higher fentanyl levels can cause excess sedation and respiratory depression.
How serious is the interaction between Fentanyl transmucosal and Metronidazole?
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, especially when metronidazole is started or stopped. Adjust the fentanyl dose if signs of opioid excess appear.
What other medicines interact with Metronidazole?
MediHelp also lists interactions of Metronidazole with, for example, Ethanol, Pimozide, Amiodarone. The full list is on the Metronidazole page.
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