Drug interactions
Fentanyl + Nirmatrelvir / ritonavir
Severity: Major
Fentanyl and Nirmatrelvir / ritonavir: major 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
Ritonavir-boosted nirmatrelvir strongly inhibits CYP3A4 and can substantially raise fentanyl concentrations. This may cause profound sedation and fatal respiratory depression.
What this interaction means in plain words
Fentanyl and Nirmatrelvir / ritonavir can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Strong CYP3A4 inhibition by ritonavir and nirmatrelvir reduces fentanyl clearance.
What to do
Reduce the fentanyl dose and monitor frequently for respiratory depression and sedation during and after the five-day course. Consider an alternative analgesic if the dose cannot be safely managed.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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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 Fentanyl with Nirmatrelvir / ritonavir?
MediHelp rates the interaction as major. Fentanyl and Nirmatrelvir / ritonavir can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Ritonavir-boosted nirmatrelvir strongly inhibits CYP3A4 and can substantially raise fentanyl concentrations. This may cause profound sedation and fatal respiratory depression.
How serious is the interaction between Fentanyl and Nirmatrelvir / ritonavir?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Reduce the fentanyl dose and monitor frequently for respiratory depression and sedation during and after the five-day course. Consider an alternative analgesic if the dose cannot be safely managed.
What other medicines interact with Fentanyl?
MediHelp also lists interactions of Fentanyl with, for example, Alvimopan, Isocarboxazid, Olanzapine / samidorphan. The full list is on the Fentanyl page.
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