Drug interactions
Carbamazepine + Tamoxifen
Severity: Major
Carbamazepine and Tamoxifen: 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
Carbamazepine induces enzymes that metabolize tamoxifen and its metabolites, lowering exposure. This may reduce anti-tumor efficacy, and the endoxifen effect is uncertain.
What this interaction means in plain words
Carbamazepine and Tamoxifen 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.
Carbamazepine belongs to Central Nervous System; Tamoxifen belongs to Endocrine.
Why it happens
Induction of CYP3A4 and CYP2C9 by carbamazepine increases tamoxifen clearance.
What to do
Avoid the combination where possible and use a non-inducing antiseizure drug. If unavoidable, consider an alternative endocrine therapy and monitor for loss of efficacy.
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 Carbamazepine
- Artemether / lumefantrine + Carbamazepine Contraindicated
- Cabotegravir + Carbamazepine Contraindicated
- Carbamazepine + Delamanid Contraindicated
- Carbamazepine + Dienogest / estradiol valerate Contraindicated
- Carbamazepine + Doravirine Contraindicated
- Carbamazepine + Elbasvir / grazoprevir Contraindicated
Other interactions of Tamoxifen
- Amiodarone + Tamoxifen Major
- Anastrozole + Tamoxifen Major
- Bupropion + Tamoxifen Major
- Cinacalcet + Tamoxifen Major
- Dacomitinib + Tamoxifen Major
- Eliglustat + Tamoxifen Major
Frequently asked questions
Can I take Carbamazepine with Tamoxifen?
MediHelp rates the interaction as major. Carbamazepine and Tamoxifen 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. Carbamazepine induces enzymes that metabolize tamoxifen and its metabolites, lowering exposure. This may reduce anti-tumor efficacy, and the endoxifen effect is uncertain.
How serious is the interaction between Carbamazepine and Tamoxifen?
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 where possible and use a non-inducing antiseizure drug. If unavoidable, consider an alternative endocrine therapy and monitor for loss of efficacy.
What other medicines interact with Carbamazepine?
MediHelp also lists interactions of Carbamazepine with, for example, Artemether / lumefantrine, Cabotegravir, Delamanid. The full list is on the Carbamazepine page.
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