Drug interactions
Fentanyl + Thioridazine
Severity: Major
Fentanyl and Thioridazine: 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
Both agents cause sedation and hypotension, and thioridazine strongly prolongs the QT interval, with risk of torsades de pointes. Opioids may add to sedation and orthostatic hypotension.
What this interaction means in plain words
Fentanyl and Thioridazine 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.
Fentanyl belongs to Musculoskeletal; Thioridazine belongs to Central Nervous System.
Why it happens
Additive CNS depression and hypotension; thioridazine also causes QT prolongation and is a CYP2D6 inhibitor.
What to do
Avoid if possible; if used, give reduced opioid doses and monitor sedation, blood pressure and ECG. Correct potassium and magnesium abnormalities.
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
Other interactions of Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Frequently asked questions
Can I take Fentanyl with Thioridazine?
MediHelp rates the interaction as major. Fentanyl and Thioridazine 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. Both agents cause sedation and hypotension, and thioridazine strongly prolongs the QT interval, with risk of torsades de pointes. Opioids may add to sedation and orthostatic hypotension.
How serious is the interaction between Fentanyl and Thioridazine?
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 if possible; if used, give reduced opioid doses and monitor sedation, blood pressure and ECG. Correct potassium and magnesium abnormalities.
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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