Abametapir and Methadone: 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 recordMethadone
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 put it on your scalp, a little gets into your body and can briefly block a liver enzyme (called CYP3A4) that helps break down other medicines. Methadone is cleared by that same enzyme.
So after using abametapir, your body may clear methadone more slowly, letting it build up. That could make methadone's effects stronger, including too much sleepiness or slowed breathing. This is a predicted concern based on how the drugs work, not a proven one, but methadone is a drug where extra caution is smart. Please talk with your pharmacist or doctor before using both so they can guide you safely.
Mechanism: Abametapir inhibits CYP3A4; methadone is a CYP3A4 substrate. Inhibition reduces methadone metabolism, increasing methadone exposure (AUC/Cmax) with a rapid onset.
Clinical effect: Potential for enhanced opioid effect, including sedation, respiratory depression, and QT-related risk.
- Evidence: Theoretical (based on abametapir's known CYP3A4 inhibition).
- Onset: Rapid; enzyme inhibition can persist for approximately 2 weeks after topical application.
- Management: Avoid CYP3A4 substrates for 2 weeks after abametapir application; if unavoidable, avoid abametapir. If both are used, consider closer monitoring for opioid toxicity.
What happens
Increased exposure of CYP3A4 substrate
Interaction Deep Dive
For a period of 2 weeks following the application of abametapir, CYP3A4 substrates should not be used. When avoiding these substrates is not possible, then abametapir itself should be avoided1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism by abametapir
How to manage this interaction
The documented guidance is straightforward: avoid using CYP3A4 substrates like methadone for about 2 weeks after applying abametapir. If avoiding methadone is not feasible, the alternative is to avoid using abametapir.
What you can do:
- Do not stop or change your methadone on your own. Methadone requires professional oversight.
- Before treating lice with abametapir, tell your pharmacist or prescriber that you take methadone so they can choose the safest option (a different lice treatment or timing).
- Watch for unusual drowsiness, confusion, or slowed breathing, and seek help right away if these occur.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Abametapir and Methadone together?
Abametapir can raise methadone levels by blocking the enzyme that clears it, so avoid using them together within 2 weeks of the lice treatment; ask your pharmacist about a safer lice option while on methadone. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abametapir and Methadone 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 Methadone interaction managed?
The documented guidance is straightforward: avoid using CYP3A4 substrates like methadone for about 2 weeks after applying abametapir. If avoiding methadone is not feasible, the alternative is to avoid using abametapir. What you can do: Do not stop or change your methadone on your own. Methadone requires professional oversight. Before treating lice with abametapir, tell your pharmacist or prescribe… 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 Methadone 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 Methadone
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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