Rifampicin and Tamoxifen: Drug Interaction Guide
Quick answer: This is a major interaction — avoid combining Rifampicin and Tamoxifen unless specifically directed by your doctor.
How Rifampicin interacts with Tamoxifen
Rifampicin strongly induces CYP3A4 and CYP2C9, reducing tamoxifen plasma exposure by approximately 86% and compromising anti-oestrogen efficacy.
What you should do
Avoid combination. Substitute a non-inducing antibiotic; if rifampicin is essential, discuss alternative endocrine therapy with oncology.
Key facts
Severity
Major — avoid combination
Mechanism
Rifampicin strongly induces CYP3A4 and CYP2C9, reducing tamoxifen plasma exposure by approximately 86% and compromising ...
Action
Avoid combination. Substitute a non-inducing antibiotic; if rifampicin is essential, discuss alternative endocrine thera...
Frequently asked questions
Can I take Rifampicin and Tamoxifen together?
No — this combination should generally be avoided. Avoid combination. Substitute a non-inducing antibiotic; if rifampicin is essential, discuss alternative endocrine therapy with oncology.
What is the severity of this interaction?
The interaction between Rifampicin and Tamoxifen is classified as Major — avoid combination. Rifampicin strongly induces CYP3A4 and CYP2C9, reducing tamoxifen plasma exposure by approximately 86% and compromising anti-oestrogen efficacy.
What should I do if I'm prescribed both?
Avoid combination. Substitute a non-inducing antibiotic; if rifampicin is essential, discuss alternative endocrine therapy with oncology. Always consult your prescribing clinician — do not stop or change medications without medical guidance.
Last reviewed: by iMedic Medical Editorial Team. Our editorial process.