Drug interactions
Fentanyl + Morphine
Severity: Major
Fentanyl and Morphine: 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
Two opioid agonists together produce additive sedation, respiratory depression and hypotension, with possible coma or death. Combinations are common in palliative or perioperative care but need careful dosing.
What this interaction means in plain words
Fentanyl and Morphine 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; Morphine belongs to Musculoskeletal.
Why it happens
Additive mu-opioid receptor agonism causing central respiratory and CNS depression.
What to do
Use the lowest effective doses for the shortest duration and monitor respiratory rate and sedation. Calculate total opioid exposure when adjusting doses.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Fentanyl and Morphine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
Other interactions of Morphine
- Alvimopan + Morphine Contraindicated
- Isocarboxazid + Morphine Contraindicated
- Morphine + Olanzapine / samidorphan Contraindicated
- Morphine + Phenelzine Contraindicated
- Morphine + Tranylcypromine Contraindicated
- Alfentanil + Morphine 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 Fentanyl with Morphine?
MediHelp rates the interaction as major. Fentanyl and Morphine 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. Two opioid agonists together produce additive sedation, respiratory depression and hypotension, with possible coma or death. Combinations are common in palliative or perioperative care but need careful dosing.
How serious is the interaction between Fentanyl and Morphine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use the lowest effective doses for the shortest duration and monitor respiratory rate and sedation. Calculate total opioid exposure when adjusting doses.
What other medicines interact with Morphine?
MediHelp also lists interactions of Morphine with, for example, Alvimopan, Isocarboxazid, Olanzapine / samidorphan. The full list is on the Morphine page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
