Drug interactions
Doxylamine + Fentanyl
Severity: Major
Doxylamine and Fentanyl: major interaction.
Last updated Sources: UK SmPC
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
Doxylamine is a sedating first-generation antihistamine, and combining it with an opioid such as fentanyl adds to sedation and respiratory depression. Impaired psychomotor function and profound drowsiness are more likely, particularly in older or opioid-naive patients.
What this interaction means in plain words
Doxylamine and Fentanyl 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.
Doxylamine belongs to Respiratory; Fentanyl belongs to Musculoskeletal.
Why it happens
Additive central nervous system depression through opioid receptor agonism and central H1 antihistamine blockade.
What to do
Avoid combining where possible, or use the lowest effective doses for the shortest time. Monitor for sedation and respiratory depression and counsel patients to avoid alcohol and driving.
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 Doxylamine and Fentanyl, 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 7 days on the web. No card needed.
References
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 Doxylamine
Frequently asked questions
Can I take Doxylamine with Fentanyl?
MediHelp rates the interaction as major. Doxylamine and Fentanyl 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. Doxylamine is a sedating first-generation antihistamine, and combining it with an opioid such as fentanyl adds to sedation and respiratory depression. Impaired psychomotor function and profound drowsiness are more likely, particularly in older or opioid-naive patients.
How serious is the interaction between Doxylamine and Fentanyl?
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 combining where possible, or use the lowest effective doses for the shortest time. Monitor for sedation and respiratory depression and counsel patients to avoid alcohol and driving.
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.
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.
