Drug interactions
Chlorpromazine + Promethazine
Severity: Major
Chlorpromazine and Promethazine: 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
The concurrent use of promethazine and chlorpromazine may lead to an increased risk of QTc interval prolongation, which can result in serious cardiac arrhythmias. Patients taking both medications should be monitored closely for signs of cardiac complications.
What this interaction means in plain words
Chlorpromazine and Promethazine 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 belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Both promethazine and chlorpromazine can affect cardiac repolarization, leading to an extended QTc interval. This interaction is primarily due to their effects on cardiac ion channels.
What to do
It is advisable to avoid using these two medications together. If co-administration is necessary, continuous cardiac monitoring should be implemented to detect any potential arrhythmias early.
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 Chlorpromazine and Promethazine, 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 Promethazine
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
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 Promethazine?
MediHelp rates the interaction as major. Chlorpromazine and Promethazine 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. The concurrent use of promethazine and chlorpromazine may lead to an increased risk of QTc interval prolongation, which can result in serious cardiac arrhythmias. Patients taking both medications should be monitored closely for signs of cardiac complications.
How serious is the interaction between Chlorpromazine and Promethazine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: It is advisable to avoid using these two medications together. If co-administration is necessary, continuous cardiac monitoring should be implemented to detect any potential arrhythmias early.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Cabergoline, Dopamine, Ibutilide. The full list is on the Promethazine 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.
