Drug interactions
Granisetron + Promethazine
Severity: Moderate
Granisetron and Promethazine: 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
Granisetron can cause small QT interval prolongation and promethazine may add to this effect. The risk of clinically significant arrhythmia is generally low but increases in patients with electrolyte abnormalities or other QT-prolonging drugs.
What this interaction means in plain words
Granisetron and Promethazine 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.
Granisetron belongs to Gastrointestinal Tract; Promethazine belongs to Respiratory.
Why it happens
Additive effects on cardiac repolarization causing QT prolongation.
What to do
Correct potassium and magnesium before use and consider an ECG in patients with cardiac disease or other QT-prolonging therapy. Otherwise combined antiemetic use is usually manageable.
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 Granisetron
- Apomorphine + Granisetron Contraindicated
- Amiodarone + Granisetron Major
- Amisulpride + Granisetron Major
- Arsenic trioxide + Granisetron Major
- Artemether / lumefantrine + Granisetron Major
- Artemether + Granisetron Major
Frequently asked questions
Can I take Granisetron with Promethazine?
MediHelp rates the interaction as moderate. Granisetron and Promethazine 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. Granisetron can cause small QT interval prolongation and promethazine may add to this effect. The risk of clinically significant arrhythmia is generally low but increases in patients with electrolyte abnormalities or other QT-prolonging drugs.
How serious is the interaction between Granisetron and Promethazine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Correct potassium and magnesium before use and consider an ECG in patients with cardiac disease or other QT-prolonging therapy. Otherwise combined antiemetic use is usually manageable.
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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