Drug interactions
Clarithromycin + Toremifene
Severity: Major
Clarithromycin and Toremifene: major interaction.
Last updated Sources: US FDA label
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
Both agents prolong the QT interval, and clarithromycin can raise toremifene levels, further increasing the risk of torsades de pointes and other serious arrhythmias.
What this interaction means in plain words
Clarithromycin and Toremifene 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.
Clarithromycin belongs to Anti Bacterial; Toremifene belongs to Endocrine.
Why it happens
Additive QT prolongation combined with CYP3A4 inhibition by clarithromycin, which reduces toremifene metabolism.
What to do
Avoid the combination and choose a non-QT-prolonging antibiotic. If unavoidable, interrupt toremifene or obtain ECGs and correct potassium and magnesium.
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
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 Toremifene
- Amiodarone + Toremifene Contraindicated
- Dronedarone + Toremifene Contraindicated
- Nilotinib + Toremifene Contraindicated
- Pimozide + Toremifene Contraindicated
- Quinidine + Toremifene Contraindicated
- Ribociclib + Toremifene Contraindicated
Frequently asked questions
Can I take Clarithromycin with Toremifene?
MediHelp rates the interaction as major. Clarithromycin and Toremifene 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. Both agents prolong the QT interval, and clarithromycin can raise toremifene levels, further increasing the risk of torsades de pointes and other serious arrhythmias.
How serious is the interaction between Clarithromycin and Toremifene?
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 and choose a non-QT-prolonging antibiotic. If unavoidable, interrupt toremifene or obtain ECGs and correct potassium and magnesium.
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.
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