Drug interactions
Cyclophosphamide + Tamoxifen
Severity: Moderate
Cyclophosphamide 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
Tamoxifen is commonly combined with cyclophosphamide-based regimens in breast cancer, but both agents are associated with venous thromboembolism, and the combination may raise that risk further. A relevant pharmacokinetic interaction through CYP3A4 is not established.
What this interaction means in plain words
Cyclophosphamide 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.
Cyclophosphamide belongs to Oncology; Tamoxifen belongs to Endocrine.
Why it happens
Additive prothrombotic effects; no established metabolic interaction.
What to do
Assess thrombosis risk before starting and watch for signs of venous thromboembolism. Consider thromboprophylaxis in patients with additional risk factors.
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 Cyclophosphamide
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 Cyclophosphamide with Tamoxifen?
MediHelp rates the interaction as moderate. Cyclophosphamide 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. Tamoxifen is commonly combined with cyclophosphamide-based regimens in breast cancer, but both agents are associated with venous thromboembolism, and the combination may raise that risk further. A relevant pharmacokinetic interaction through CYP3A4 is not established.
How serious is the interaction between Cyclophosphamide 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: Assess thrombosis risk before starting and watch for signs of venous thromboembolism. Consider thromboprophylaxis in patients with additional risk factors.
What other medicines interact with Cyclophosphamide?
MediHelp also lists interactions of Cyclophosphamide with, for example, Adenovirus types 4 and 7 live, Belatacept, Bendamustine. The full list is on the Cyclophosphamide page.
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