Drug interactions
Ivosidenib + Tamoxifen
Severity: Major
Ivosidenib and Tamoxifen: major interaction.
Last updated Sources: UK SmPC
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
Ivosidenib induces CYP3A4 and may lower tamoxifen and its metabolite concentrations, potentially reducing efficacy. Ivosidenib can also prolong the QT interval, and tamoxifen has a similar effect.
What this interaction means in plain words
Ivosidenib 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.
Ivosidenib belongs to Oncology; Tamoxifen belongs to Endocrine.
Why it happens
CYP3A4 induction by ivosidenib increases tamoxifen clearance, with additive QT prolongation.
What to do
Avoid the combination where possible. If unavoidable, monitor ECG and electrolytes and watch for loss of tamoxifen 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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References
- Nolvadex 20 mg Film-Coated Tablet - SmPC sections 4.3/4.5 (class statement: other medicinal products known to prolong the QT interval; "the concomitant use of Nolvadex with other medicinal products known to prolong the QT interval may further potentiate QT prolongation") — electronic medicines compendium (UK SmPC)
Other interactions of Tamoxifen
- Amiodarone + Tamoxifen Major
- Anastrozole + Tamoxifen Major
- Bupropion + Tamoxifen Major
- Carbamazepine + Tamoxifen Major
- Cinacalcet + Tamoxifen Major
- Dacomitinib + Tamoxifen Major
Other interactions of Ivosidenib
- Alfuzosin + Ivosidenib Major
- Amiodarone + Ivosidenib Major
- Amisulpride + Ivosidenib Major
- Amitriptyline + Ivosidenib Major
- Amobarbital + Ivosidenib Major
- Anagrelide + Ivosidenib Major
Frequently asked questions
Can I take Ivosidenib with Tamoxifen?
MediHelp rates the interaction as major. Ivosidenib 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. Ivosidenib induces CYP3A4 and may lower tamoxifen and its metabolite concentrations, potentially reducing efficacy. Ivosidenib can also prolong the QT interval, and tamoxifen has a similar effect.
How serious is the interaction between Ivosidenib 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. If unavoidable, monitor ECG and electrolytes and watch for loss of tamoxifen efficacy.
What other medicines interact with Tamoxifen?
MediHelp also lists interactions of Tamoxifen with, for example, Amiodarone, Anastrozole, Bupropion. The full list is on the Tamoxifen page.
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