Drug interactions
Sulfamethoxazole + Tamoxifen
Severity: Minor
Sulfamethoxazole and Tamoxifen: minor 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
Sulfamethoxazole inhibits CYP2C9 and may modestly alter tamoxifen metabolism. The clinical significance is uncertain and likely small, especially during short antibiotic courses.
What this interaction means in plain words
Sulfamethoxazole and Tamoxifen have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Why it happens
Sulfamethoxazole inhibits CYP2C9, which contributes to tamoxifen biotransformation.
What to do
No routine change is needed for short courses. Be aware of the interaction if prolonged therapy is planned.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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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 Sulfamethoxazole with Tamoxifen?
MediHelp rates the interaction as minor. Sulfamethoxazole and Tamoxifen have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Sulfamethoxazole inhibits CYP2C9 and may modestly alter tamoxifen metabolism. The clinical significance is uncertain and likely small, especially during short antibiotic courses.
How serious is the interaction between Sulfamethoxazole and Tamoxifen?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No routine change is needed for short courses. Be aware of the interaction if prolonged therapy is planned.
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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