Drug interactions
Chlorpromazine + Diamorphine
Severity: Major
Chlorpromazine and Diamorphine: 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
Chlorpromazine can potentiate the sedative, hypotensive and respiratory depressant effects of diamorphine (heroin). This may lead to profound sedation or respiratory depression.
What this interaction means in plain words
Chlorpromazine 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 opioid agonism and phenothiazine sedation, with additive hypotension from alpha-adrenergic blockade.
What to do
Start with reduced doses and titrate carefully, monitoring sedation, respiratory rate and blood pressure. Ensure naloxone and resuscitation equipment are available.
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
- Chlorpromazine 100mg Tablets - SmPC sections 4.3/4.5 (class statement: morphine derivatives; "Other CNS depressants: morphine derivatives (analgesics, antitussives and substitution treatments), barbiturates, benzodiazepines, anxiolytics other than benzod") — electronic medicines compendium (UK SmPC)
Other interactions of Chlorpromazine
- Chlorpromazine + Dofetilide Contraindicated
- Chlorpromazine + Dronedarone Contraindicated
- Chlorpromazine + Droperidol Contraindicated
- Chlorpromazine + Ibutilide Contraindicated
- Chlorpromazine + Metrizamide Contraindicated
- Chlorpromazine + Panobinostat Contraindicated
Frequently asked questions
Can I take Chlorpromazine with Diamorphine?
MediHelp rates the interaction as major. Chlorpromazine 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. Chlorpromazine can potentiate the sedative, hypotensive and respiratory depressant effects of diamorphine (heroin). This may lead to profound sedation or respiratory depression.
How serious is the interaction between Chlorpromazine 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: Start with reduced doses and titrate carefully, monitoring sedation, respiratory rate and blood pressure. Ensure naloxone and resuscitation equipment are available.
What other medicines interact with Chlorpromazine?
MediHelp also lists interactions of Chlorpromazine with, for example, Dofetilide, Dronedarone, Droperidol. The full list is on the Chlorpromazine page.
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