Drug interactions
Pimozide + Promethazine
Severity: Contraindicated
Pimozide and Promethazine: contraindicated 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
Both drugs can prolong the QT interval, and pimozide in particular carries a substantial risk of torsades de pointes. Giving them together increases the chance of serious ventricular arrhythmia and sudden cardiac death.
What this interaction means in plain words
Pimozide and Promethazine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Pimozide belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive blockade of cardiac hERG potassium channels leading to QT prolongation.
What to do
Avoid the combination and choose a non-QT-prolonging antihistamine or antiemetic. If unavoidable, obtain a baseline ECG and correct potassium and magnesium first.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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Other interactions of Promethazine
- Ibutilide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
- Belladonna and opium + Promethazine Major
Other interactions of Pimozide
- Adagrasib + Pimozide Contraindicated
- Amiodarone + Pimozide Contraindicated
- Amisulpride + Pimozide Contraindicated
- Amitriptyline + Pimozide Contraindicated
- Amoxapine + Pimozide Contraindicated
- Anagrelide + Pimozide Contraindicated
Frequently asked questions
Can I take Pimozide with Promethazine?
MediHelp rates the interaction as contraindicated. Pimozide and Promethazine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Both drugs can prolong the QT interval, and pimozide in particular carries a substantial risk of torsades de pointes. Giving them together increases the chance of serious ventricular arrhythmia and sudden cardiac death.
How serious is the interaction between Pimozide and Promethazine?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination and choose a non-QT-prolonging antihistamine or antiemetic. If unavoidable, obtain a baseline ECG and correct potassium and magnesium first.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Thioridazine, Alfentanil. The full list is on the Promethazine page.
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