Drug interactions
Fentanyl transdermal + Ketoconazole
Severity: Major
Fentanyl transdermal and Ketoconazole: 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
Ketoconazole reduces fentanyl clearance, and with patches the effect can build slowly and persist after the inhibitor is stopped. This can lead to life-threatening respiratory depression and sedation.
What this interaction means in plain words
Fentanyl transdermal and Ketoconazole 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 decreases fentanyl metabolism.
What to do
Avoid the combination if possible; otherwise monitor closely for respiratory depression and sedation for an extended period and adjust the patch dose.
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 Ketoconazole
- Alfuzosin + Ketoconazole Contraindicated
- Alprazolam + Ketoconazole Contraindicated
- Avanafil + Ketoconazole Contraindicated
- Conivaptan + Ketoconazole Contraindicated
- Dihydroergotamine intranasal + Ketoconazole Contraindicated
- Dihydroergotamine + Ketoconazole Contraindicated
Frequently asked questions
Can I take Fentanyl transdermal with Ketoconazole?
MediHelp rates the interaction as major. Fentanyl transdermal and Ketoconazole 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. Ketoconazole reduces fentanyl clearance, and with patches the effect can build slowly and persist after the inhibitor is stopped. This can lead to life-threatening respiratory depression and sedation.
How serious is the interaction between Fentanyl transdermal and Ketoconazole?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination if possible; otherwise monitor closely for respiratory depression and sedation for an extended period and adjust the patch dose.
What other medicines interact with Ketoconazole?
MediHelp also lists interactions of Ketoconazole with, for example, Alfuzosin, Alprazolam, Avanafil. The full list is on the Ketoconazole page.
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