Drug interactions
Promethazine + Valbenazine
Severity: Moderate
Promethazine and Valbenazine: moderate 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
Valbenazine can prolong the QT interval at higher exposures, and promethazine has been associated with QT prolongation as well. Both also cause sedation, so combined use may add to somnolence and arrhythmia risk in predisposed patients.
What this interaction means in plain words
Promethazine and Valbenazine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Promethazine belongs to Respiratory; Valbenazine belongs to Central Nervous System.
Why it happens
Additive QT prolongation and CNS depression.
What to do
Consider baseline and follow-up ECG in patients with cardiac risk factors or other QT-prolonging drugs. Monitor for excessive sedation.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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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 Valbenazine
- Deutetrabenazine + Valbenazine Contraindicated
- Tranylcypromine + Valbenazine Contraindicated
- Amiodarone + Valbenazine Major
- Amisulpride + Valbenazine Major
- Apalutamide + Valbenazine Major
- Carbamazepine + Valbenazine Major
Frequently asked questions
Can I take Promethazine with Valbenazine?
MediHelp rates the interaction as moderate. Promethazine and Valbenazine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Valbenazine can prolong the QT interval at higher exposures, and promethazine has been associated with QT prolongation as well. Both also cause sedation, so combined use may add to somnolence and arrhythmia risk in predisposed patients.
How serious is the interaction between Promethazine and Valbenazine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Consider baseline and follow-up ECG in patients with cardiac risk factors or other QT-prolonging drugs. Monitor for excessive 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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