Abametapir and Trabectedin: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jun 30, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Abametapir
No brand names on recordTrabectedin
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.
Abametapir is a lotion used to treat head lice. Even though it's applied to the scalp, some of it gets into your body and can temporarily slow down a liver enzyme called CYP3A4. That enzyme is one of the main ways your body breaks down trabectedin (Yondelis), a chemotherapy medicine.
If both are used close together, trabectedin could build up higher than expected, which may raise the risk of its side effects. The good news is this is easy to plan around. Talk with your oncology team and pharmacist before using any lice treatment so they can time things safely.
Mechanism: Abametapir inhibits CYP3A4. Trabectedin is a CYP3A4 substrate (not a prodrug), so inhibition reduces its metabolism and increases systemic exposure (AUC/Cmax), with rapid onset.
Consequence: Elevated trabectedin exposure may amplify dose-dependent toxicities (myelosuppression, hepatotoxicity, rhabdomyolysis).
Evidence: Theoretical, but severity rated major given the narrow tolerability of trabectedin.
- Avoid CYP3A4 substrates for 2 weeks after abametapir application.
- If concurrent use is unavoidable, avoid abametapir instead.
- Monitor CBC and hepatic parameters if co-exposure occurs.
What happens
Increased exposure of CYP3A4 substrate
Interaction Deep Dive
For a period of 2 weeks following abametapir application, refrain from using CYP3A4 substrates. Should that not be possible, do not use abametapir1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism by abametapir
How to manage this interaction
This interaction is best handled by timing and coordination rather than any dose change you make yourself.
- Keep both medicines as prescribed and do not stop your chemotherapy.
- Before using any head lice product, tell your oncology team and pharmacist that you take trabectedin.
- The general guidance is to avoid CYP3A4-cleared drugs (like trabectedin) for about 2 weeks after applying abametapir. If that timing isn't workable, your team may choose a different lice treatment instead.
- If both must overlap, your team may monitor you more closely with blood counts and liver tests.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Abametapir and Trabectedin together?
Abametapir can slow the breakdown of trabectedin and raise its levels, so avoid trabectedin for about 2 weeks after using abametapir, or use a different lice treatment. Let your oncology team and pharmacist coordinate the timing. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abametapir and Trabectedin interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How is the Abametapir and Trabectedin interaction managed?
This interaction is best handled by timing and coordination rather than any dose change you make yourself. Keep both medicines as prescribed and do not stop your chemotherapy. Before using any head lice product, tell your oncology team and pharmacist that you take trabectedin. The general guidance is to avoid CYP3A4-cleared drugs (like trabectedin) for about 2 weeks after applying abametapir. If t… 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 Abametapir or Trabectedin 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: XEGLYZE(TM) topical lotion, abametapir topical lotion. Dr Reddy’s Laboratories Inc (per FDA), Princeton, NJ, 2020. DailyMed
Keep reading about Abametapir
Keep reading about Trabectedin
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