Drug interactions
Promethazine + Tetrabenazine
Severity: Major
Promethazine and Tetrabenazine: 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
Tetrabenazine can prolong the QT interval modestly, and promethazine may also contribute to QT prolongation. The combination raises arrhythmia risk. Both drugs are sedating, and promethazine's D2 blockade adds to the risk of parkinsonism and depression-related effects.
What this interaction means in plain words
Promethazine and Tetrabenazine 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.
Promethazine belongs to Respiratory; Tetrabenazine belongs to Central Nervous System.
Why it happens
Additive QT prolongation and additive sedation, with D2 blockade added to presynaptic dopamine depletion.
What to do
Avoid the combination and choose another antiemetic or antihistamine. If used, monitor ECG, electrolytes, sedation and extrapyramidal symptoms.
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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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 Tetrabenazine
- Dronedarone + Tetrabenazine Contraindicated
- Isocarboxazid + Tetrabenazine Contraindicated
- Linezolid + Tetrabenazine Contraindicated
- Phenelzine + Tetrabenazine Contraindicated
- Pimozide + Tetrabenazine Contraindicated
- Procarbazine + Tetrabenazine Contraindicated
Frequently asked questions
Can I take Promethazine with Tetrabenazine?
MediHelp rates the interaction as major. Promethazine and Tetrabenazine 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. Tetrabenazine can prolong the QT interval modestly, and promethazine may also contribute to QT prolongation. The combination raises arrhythmia risk. Both drugs are sedating, and promethazine's D2 blockade adds to the risk of parkinsonism and depression-related effects.
How serious is the interaction between Promethazine and Tetrabenazine?
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 the combination and choose another antiemetic or antihistamine. If used, monitor ECG, electrolytes, sedation and extrapyramidal symptoms.
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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