Drug interactions
Chlorzoxazone + Fentanyl transdermal
Severity: Major
Chlorzoxazone and Fentanyl transdermal: major interaction.
Last updated Sources: US FDA label
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
Transdermal fentanyl with a muscle relaxant can cause profound sedation and respiratory depression. Fentanyl exposure persists after patch removal, so the risk lasts for some time.
What this interaction means in plain words
Chlorzoxazone and Fentanyl transdermal 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 CNS and respiratory depression through pharmacodynamic synergism.
What to do
Avoid if possible; otherwise use the lowest doses and monitor for sedation and respiratory depression, including after patch removal.
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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References
Other interactions of Chlorzoxazone
Frequently asked questions
Can I take Chlorzoxazone with Fentanyl transdermal?
MediHelp rates the interaction as major. Chlorzoxazone and Fentanyl transdermal 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. Transdermal fentanyl with a muscle relaxant can cause profound sedation and respiratory depression. Fentanyl exposure persists after patch removal, so the risk lasts for some time.
How serious is the interaction between Chlorzoxazone and Fentanyl transdermal?
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; otherwise use the lowest doses and monitor for sedation and respiratory depression, including after patch removal.
What other medicines interact with Chlorzoxazone?
MediHelp also lists interactions of Chlorzoxazone with, for example, Alfentanil, Alprazolam, Amobarbital. The full list is on the Chlorzoxazone page.
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