Drug interactions
Chlorpromazine + Tamoxifen
Severity: Moderate
Chlorpromazine and Tamoxifen: 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
Chlorpromazine inhibits CYP2D6, the enzyme that converts tamoxifen to its active metabolite endoxifen, which may reduce tamoxifen efficacy. Both drugs can also prolong the QT interval.
What this interaction means in plain words
Chlorpromazine and Tamoxifen 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.
Chlorpromazine belongs to Central Nervous System; Tamoxifen belongs to Endocrine.
Why it happens
CYP2D6 inhibition by chlorpromazine decreases endoxifen formation, with additive QT effects.
What to do
Where possible, select an antipsychotic with little CYP2D6 inhibition for patients taking tamoxifen for breast cancer treatment or prevention. Obtain an ECG if QT risk factors exist.
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 Chlorpromazine
- Chlorpromazine + Dofetilide Contraindicated
- Chlorpromazine + Dronedarone Contraindicated
- Chlorpromazine + Droperidol Contraindicated
- Chlorpromazine + Ibutilide Contraindicated
- Chlorpromazine + Metrizamide Contraindicated
- Chlorpromazine + Panobinostat Contraindicated
Other interactions of Tamoxifen
- Amiodarone + Tamoxifen Major
- Anastrozole + Tamoxifen Major
- Bupropion + Tamoxifen Major
- Carbamazepine + Tamoxifen Major
- Cinacalcet + Tamoxifen Major
- Dacomitinib + Tamoxifen Major
Frequently asked questions
Can I take Chlorpromazine with Tamoxifen?
MediHelp rates the interaction as moderate. Chlorpromazine and Tamoxifen 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. Chlorpromazine inhibits CYP2D6, the enzyme that converts tamoxifen to its active metabolite endoxifen, which may reduce tamoxifen efficacy. Both drugs can also prolong the QT interval.
How serious is the interaction between Chlorpromazine and Tamoxifen?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Where possible, select an antipsychotic with little CYP2D6 inhibition for patients taking tamoxifen for breast cancer treatment or prevention. Obtain an ECG if QT risk factors exist.
What other medicines interact with Chlorpromazine?
MediHelp also lists interactions of Chlorpromazine with, for example, Dofetilide, Dronedarone, Droperidol. The full list is on the Chlorpromazine page.
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