Imlunestrant and Colchicine: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Colchicine
Imlunestrant
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Here's what's going on. Colchicine leaves your body partly through a kind of cellular "pump" called P-gp. Imlunestrant can slow that pump down. When the pump is slowed, more colchicine can build up in your body than usual, and that can raise the chance of colchicine side effects like nausea, diarrhea, stomach cramps, and muscle problems.
Colchicine is a medicine where the safe range is narrow, so even a modest rise matters. The good news is that this is very manageable. Don't stop or change either medicine on your own. Just let your pharmacist or doctor know you take both, and they can adjust your dose and keep a closer eye on you.
Mechanism: Imlunestrant inhibits P-gp-mediated efflux; colchicine is a P-gp substrate with a narrow therapeutic index. Inhibition reduces colchicine efflux, increasing systemic exposure and risk of colchicine toxicity (GI, myelosuppression, neuromyopathy). Neither drug is a prodrug; this is a direct PK increase in the active substrate.
- Direction: increased colchicine exposure (AUC/Cmax).
- Magnitude: not quantified for colchicine; imlunestrant raised digoxin AUC 1.4-fold and Cmax 1.6-fold.
- Evidence: theoretical/extrapolated. Onset: unspecified.
- Management: avoid concomitant use with NTI P-gp substrates; if unavoidable, individualize colchicine dose and monitor closely, particularly in renal/hepatic impairment.
What happens
Increased P-gp substrate exposure and an increased risk of P-gp substrate-related adverse reactions
Interaction Deep Dive
Imlunestrant, which inhibits P-gp, should not be given together with P-gp substrates that have a narrow therapeutic index, because such combinations can raise the exposure of these substrates and thereby heighten the likelihood of adverse reactions associated with them. A drug interaction study demonstrated that co-administering imlunestrant with the P-gp substrate digoxin raised digoxin AUC by 1.4-fold and Cmax by 1.6-fold1.
Why it happens (mechanism)
Inhibition of P-gp-mediated efflux transport of imlunestrant
How to manage this interaction
What your care team may do:
- Consider whether the combination should be avoided, since colchicine is a narrow-margin drug affected by imlunestrant's P-gp inhibition.
- If both are needed, your colchicine dose may be adjusted and individualized by your care team.
- Monitor you more closely for colchicine side effects such as diarrhea, nausea, muscle weakness or pain.
What you should do: Keep taking both exactly as prescribed unless told otherwise, and make sure your pharmacist and prescriber know you take them together. Report any new stomach upset, muscle aches, or unusual tiredness promptly.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a drug interaction study, coadministration of imlunestrant with digoxin (a P-gp substrate) raised digoxin AUC by 1.4-fold and Cmax by 1.6-fold, respectively 1.
Common questions
Can I take Imlunestrant and Colchicine together?
Imlunestrant can raise colchicine levels and side-effect risk, and because colchicine has a narrow safety margin this combination is best avoided or closely managed. Tell your pharmacist or doctor you take both so they can adjust the dose and monitor you. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Imlunestrant and Colchicine interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Imlunestrant and Colchicine interaction managed?
What your care team may do: Consider whether the combination should be avoided, since colchicine is a narrow-margin drug affected by imlunestrant's P-gp inhibition. If both are needed, your colchicine dose may be adjusted and individualized by your care team. Monitor you more closely for colchicine side effects such as diarrhea, nausea, muscle weakness or pain. What you should do: Keep taking both… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Imlunestrant or Colchicine need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Product Information: INLURIYO oral tablets, imlunestrant oral tablets. Lilly USA, LLC (per FDA), Indianapolis, IN, 2025. DailyMed
Keep reading about Colchicine
Keep reading about Imlunestrant
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