Drug interactions
Mifepristone + Promethazine
Severity: Moderate
Mifepristone 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
Mifepristone is an inhibitor of several CYP enzymes and may raise promethazine exposure. Higher levels could increase sedation, anticholinergic effects and QT prolongation risk. Promethazine is also a QT-prolonging phenothiazine, and mifepristone itself can prolong QT.
What this interaction means in plain words
Mifepristone 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.
Mifepristone belongs to Endocrine; Promethazine belongs to Respiratory.
Why it happens
Mifepristone inhibits hepatic CYP metabolism of promethazine and both drugs may have additive QT effects.
What to do
Monitor for excessive sedation and anticholinergic effects, and consider an ECG if the patient has other QT risk factors. Use the lowest effective promethazine dose.
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
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Other interactions of Mifepristone
- Apixaban + Mifepristone Contraindicated
- Argatroban + Mifepristone Contraindicated
- Cisapride + Mifepristone Contraindicated
- Cortisone + Mifepristone Contraindicated
- Cyclosporin + Mifepristone Contraindicated
- Dabigatran etexilate + Mifepristone Contraindicated
Frequently asked questions
Can I take Mifepristone with Promethazine?
MediHelp rates the interaction as moderate. Mifepristone 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. Mifepristone is an inhibitor of several CYP enzymes and may raise promethazine exposure. Higher levels could increase sedation, anticholinergic effects and QT prolongation risk. Promethazine is also a QT-prolonging phenothiazine, and mifepristone itself can prolong QT.
How serious is the interaction between Mifepristone 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: Monitor for excessive sedation and anticholinergic effects, and consider an ECG if the patient has other QT risk factors. Use the lowest effective promethazine dose.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Cabergoline, Dopamine, Ibutilide. The full list is on the Promethazine page.
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