Drug interactions
Clemastine + Fentanyl intranasal
Severity: Major
Clemastine and Fentanyl intranasal: 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
Fentanyl is a potent opioid and clemastine is a sedating antimuscarinic antihistamine. Together they increase sedation and may raise the risk of respiratory depression, and additive anticholinergic effects can worsen urinary retention and constipation, potentially leading to ileus.
What this interaction means in plain words
Clemastine and Fentanyl intranasal 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
Additive central nervous system and respiratory depression plus additive antimuscarinic effects on gut and bladder.
What to do
Use the lowest effective doses and monitor sedation and respiratory rate. Monitor for constipation and urinary retention and consider a non-sedating antihistamine.
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 Clemastine
Frequently asked questions
Can I take Clemastine with Fentanyl intranasal?
MediHelp rates the interaction as major. Clemastine and Fentanyl intranasal 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 is a potent opioid and clemastine is a sedating antimuscarinic antihistamine. Together they increase sedation and may raise the risk of respiratory depression, and additive anticholinergic effects can worsen urinary retention and constipation, potentially leading to ileus.
How serious is the interaction between Clemastine and Fentanyl intranasal?
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 and monitor sedation and respiratory rate. Monitor for constipation and urinary retention and consider a non-sedating antihistamine.
What other medicines interact with Clemastine?
MediHelp also lists interactions of Clemastine with, for example, Alfentanil, Benzhydrocodone / acetaminophen, Buprenorphine buccal. The full list is on the Clemastine page.
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