Abametapir and Warfarin: 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 recordWarfarin
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 you only put it on your scalp, a little can get into your body and briefly slow down a liver enzyme called CYP1A2 that helps break down other medicines.
Warfarin (Coumadin, Jantoven) is a blood thinner that your body partly clears through that same enzyme. If it is cleared more slowly, more warfarin could build up, which may make your blood thinner than intended and raise your risk of bleeding or bruising. This concern is based on how the drug is expected to behave, not on real-world reports. The good news is your care team can manage this safely, so let your pharmacist or doctor know before either treatment is started.
Mechanism: Abametapir inhibits CYP1A2. Warfarin is partly metabolized via CYP1A2 (the R-enantiomer), so inhibition may increase warfarin exposure and enhance its anticoagulant effect.
- Direction: Increased warfarin effect (higher INR, bleeding risk).
- Evidence: Theoretical; no clinical outcome data. Magnitude not quantified.
- Onset: Unspecified; enzyme inhibition may persist up to ~2 weeks after a single application.
- NTI drug: Warfarin, so even modest exposure changes are clinically relevant.
Management: Per labeling, avoid CYP1A2 substrates for 2 weeks after abametapir; if unavoidable, avoid abametapir. If both are used, monitor INR more closely and individualize warfarin dosing.
What happens
Increased exposure of CYP1A2 substrates
Interaction Deep Dive
Do not administer CYP1A2 substrates for a period of 2 weeks following the application of abametapir. Should this not be possible, abametapir itself should be avoided 1.
Why it happens (mechanism)
Inhibition of CYP1A2-mediated metabolism by abametapir
How to manage this interaction
Keep taking your warfarin exactly as prescribed. Do not stop or change it on your own.
- Tell your pharmacist or prescriber before using abametapir lice lotion if you take warfarin.
- Guidance is to avoid CYP1A2 substrates like warfarin for 2 weeks after applying abametapir; if that is not possible, your team may choose to avoid the abametapir instead.
- If both are needed, your care team may check your INR more often and individualize your warfarin dose during that window.
- Report unusual bruising, nosebleeds, blood in urine or stool, or bleeding that will not stop.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Abametapir and Warfarin together?
Abametapir may slow warfarin's breakdown and increase bleeding risk, so avoid using them together for two weeks after applying the lice lotion and let your pharmacist or doctor guide timing and INR checks. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abametapir and Warfarin 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 Abametapir and Warfarin interaction managed?
Keep taking your warfarin exactly as prescribed. Do not stop or change it on your own. Tell your pharmacist or prescriber before using abametapir lice lotion if you take warfarin. Guidance is to avoid CYP1A2 substrates like warfarin for 2 weeks after applying abametapir; if that is not possible, your team may choose to avoid the abametapir instead. If both are needed, your care team may check your… 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Abametapir or Warfarin 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 Warfarin
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