Drug interactions
Chlorzoxazone + Diamorphine
Severity: Major
Chlorzoxazone and Diamorphine: major interaction.
Last updated Sources: Health Canada product monograph
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
Diamorphine (heroin) is a strong opioid and chlorzoxazone adds to its central depressant effects. Concurrent use increases the risk of profound sedation, respiratory depression and coma.
What this interaction means in plain words
Chlorzoxazone and Diamorphine 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 from mu-opioid receptor agonism and central muscle relaxation.
What to do
Reserve concurrent use for patients without alternatives, using the lowest doses and monitoring sedation and respiratory rate closely. Counsel the patient and caregivers on warning signs of overdose.
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 Diamorphine?
MediHelp rates the interaction as major. Chlorzoxazone and Diamorphine 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. Diamorphine (heroin) is a strong opioid and chlorzoxazone adds to its central depressant effects. Concurrent use increases the risk of profound sedation, respiratory depression and coma.
How serious is the interaction between Chlorzoxazone and Diamorphine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Reserve concurrent use for patients without alternatives, using the lowest doses and monitoring sedation and respiratory rate closely. Counsel the patient and caregivers on warning signs of overdose.
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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