Drug interactions
Clarithromycin + Tamoxifen
Severity: Moderate
Clarithromycin 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
Clarithromycin may reduce conversion of tamoxifen to N-desmethyltamoxifen and increase tamoxifen levels. Both drugs can prolong the QT interval, though the effect with tamoxifen is small. Clinical significance of the change is uncertain.
What this interaction means in plain words
Clarithromycin 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.
Clarithromycin belongs to Anti Bacterial; Tamoxifen belongs to Endocrine.
Why it happens
Inhibition of CYP3A4 alters tamoxifen metabolism, with minor additive QT effects.
What to do
Prefer a non-CYP3A4-inhibiting antibiotic for longer courses. For short courses, monitor ECG in patients with other QT 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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Clarithromycin and Tamoxifen, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Clarithromycin
- Astemizole + Clarithromycin Contraindicated
- Avanafil + Clarithromycin Contraindicated
- Cisapride + Clarithromycin Contraindicated
- Clarithromycin + Colchicine Contraindicated
- Clarithromycin + Conivaptan Contraindicated
- Clarithromycin + Dihydroergotamine Contraindicated
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 Clarithromycin with Tamoxifen?
MediHelp rates the interaction as moderate. Clarithromycin 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. Clarithromycin may reduce conversion of tamoxifen to N-desmethyltamoxifen and increase tamoxifen levels. Both drugs can prolong the QT interval, though the effect with tamoxifen is small. Clinical significance of the change is uncertain.
How serious is the interaction between Clarithromycin 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: Prefer a non-CYP3A4-inhibiting antibiotic for longer courses. For short courses, monitor ECG in patients with other QT risk factors.
What other medicines interact with Clarithromycin?
MediHelp also lists interactions of Clarithromycin with, for example, Astemizole, Avanafil, Cisapride. The full list is on the Clarithromycin page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
