Drug interactions
Cimetidine + Lonafarnib
Severity: Major
Cimetidine and Lonafarnib: major 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
Lonafarnib is a sensitive CYP3A substrate, and cimetidine weakly inhibits CYP3A4. Higher lonafarnib exposure may increase gastrointestinal toxicity, and cardiac effects are a concern.
What this interaction means in plain words
Cimetidine and Lonafarnib 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.
Cimetidine belongs to Gastrointestinal Tract; Lonafarnib belongs to Miscellaneous.
Why it happens
Cimetidine inhibition of CYP3A4-mediated metabolism of lonafarnib.
What to do
Prefer an alternative acid suppressant with no CYP3A inhibition. If unavoidable, keep lonafarnib at the starting dose and monitor for palpitations, syncope, and arrhythmia.
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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Other interactions of Cimetidine
- Cimetidine + Dofetilide Contraindicated
- Cimetidine + Fezolinetant Contraindicated
- Alfentanil + Cimetidine Major
- Atazanavir + Cimetidine Major
- Carmustine + Cimetidine Major
- Cimetidine + Citalopram Major
Other interactions of Lonafarnib
- Alfuzosin + Lonafarnib Contraindicated
- Amobarbital + Lonafarnib Contraindicated
- Apalutamide + Lonafarnib Contraindicated
- Bosentan + Lonafarnib Contraindicated
- Carbamazepine + Lonafarnib Contraindicated
- Clarithromycin + Lonafarnib Contraindicated
Frequently asked questions
Can I take Cimetidine with Lonafarnib?
MediHelp rates the interaction as major. Cimetidine and Lonafarnib 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. Lonafarnib is a sensitive CYP3A substrate, and cimetidine weakly inhibits CYP3A4. Higher lonafarnib exposure may increase gastrointestinal toxicity, and cardiac effects are a concern.
How serious is the interaction between Cimetidine and Lonafarnib?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Prefer an alternative acid suppressant with no CYP3A inhibition. If unavoidable, keep lonafarnib at the starting dose and monitor for palpitations, syncope, and arrhythmia.
What other medicines interact with Cimetidine?
MediHelp also lists interactions of Cimetidine with, for example, Dofetilide, Fezolinetant, Alfentanil. The full list is on the Cimetidine page.
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