Drug interactions
Prochlorperazine + Promethazine
Severity: Major
Prochlorperazine and Promethazine: 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
Both are phenothiazines used as antiemetics, with additive sedation, anticholinergic effects and QT prolongation. Together they increase the risk of arrhythmia and extrapyramidal reactions and offer little therapeutic benefit over a single agent.
What this interaction means in plain words
Prochlorperazine 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.
Prochlorperazine belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive QT prolongation, dopamine and histamine receptor blockade and CNS depression.
What to do
Avoid using both; choose one antiemetic or a different class such as a 5-HT3 antagonist with ECG attention. If both are used, monitor ECG and sedation.
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 Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Other interactions of Prochlorperazine
- Dronedarone + Prochlorperazine Contraindicated
- Ibutilide + Prochlorperazine Contraindicated
- Nilotinib + Prochlorperazine Contraindicated
- Pimozide + Prochlorperazine Contraindicated
- Prochlorperazine + Thioridazine Contraindicated
- Amiodarone + Prochlorperazine Major
Frequently asked questions
Can I take Prochlorperazine with Promethazine?
MediHelp rates the interaction as major. Prochlorperazine 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. Both are phenothiazines used as antiemetics, with additive sedation, anticholinergic effects and QT prolongation. Together they increase the risk of arrhythmia and extrapyramidal reactions and offer little therapeutic benefit over a single agent.
How serious is the interaction between Prochlorperazine 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: Avoid using both; choose one antiemetic or a different class such as a 5-HT3 antagonist with ECG attention. If both are used, monitor ECG and sedation.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Promethazine page.
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