Drug interactions
Clemastine + Diamorphine
Severity: Major
Clemastine and Diamorphine: 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
Diamorphine (heroin) is a potent opioid, and a sedating antihistamine adds to sedation and impaired alertness. Respiratory depression and profound sedation are possible, particularly at higher doses.
What this interaction means in plain words
Clemastine 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 the opioid agonist and the sedating H1 antihistamine.
What to do
Use the lowest effective doses and monitor sedation and respiratory rate. Prefer a non-sedating antihistamine when one is needed.
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 Clemastine and Diamorphine, 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.
Other interactions of Clemastine
Frequently asked questions
Can I take Clemastine with Diamorphine?
MediHelp rates the interaction as major. Clemastine 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 potent opioid, and a sedating antihistamine adds to sedation and impaired alertness. Respiratory depression and profound sedation are possible, particularly at higher doses.
How serious is the interaction between Clemastine 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: Use the lowest effective doses and monitor sedation and respiratory rate. Prefer a non-sedating antihistamine when one is needed.
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.
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.
