Abametapir and Amprenavir: 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 recordAmprenavir
No brand names on record
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 goes on your scalp, a little can get into your body and briefly slow down a liver enzyme (called CYP3A4) that helps break down many medicines. Amprenavir, an HIV medication, is cleared by that same enzyme.
So if you use abametapir, your body may not clear amprenavir as quickly, and levels could build up, which may lead to more side effects. The good news: this effect is short-lived, and your care team can plan around it. Please talk with your pharmacist or doctor before using both so they can guide the timing.
Mechanism: Abametapir inhibits CYP3A4. Amprenavir is a CYP3A4 substrate, so co-use is predicted to reduce its metabolism and increase systemic exposure (AUC/Cmax), potentially amplifying dose-related effects and toxicity.
- Direction: Increased amprenavir exposure (neither drug is a prodrug here in a way that reverses this).
- Onset: Rapid; enzyme inhibition can persist, so the caution window extends up to 2 weeks post-application.
- Evidence: Theoretical.
- Management: Avoid CYP3A4 substrates for 2 weeks after abametapir; if unavoidable, avoid abametapir. Consider closer monitoring if concurrent use cannot be avoided.
What happens
Increased exposure of CYP3A4 substrate
Interaction Deep Dive
For a period of 2 weeks following abametapir application, do not use CYP3A4 substrates. Should avoiding these substrates not be practical, abametapir itself should be avoided1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism by abametapir
How to manage this interaction
This interaction is manageable with good planning. Here is what typically happens:
- Your care team will usually separate these in time. Abametapir's enzyme-slowing effect can last up to 2 weeks after the scalp application, so they may avoid CYP3A4 medicines like amprenavir during that window.
- If avoiding amprenavir is not possible, the team may instead choose a different lice treatment.
- Keep taking your HIV medicine as prescribed, and do not stop anything on your own.
Before using abametapir, tell your pharmacist or prescriber you take amprenavir so they can arrange the safest timing and monitor you if needed.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Abametapir and Amprenavir together?
Abametapir can raise amprenavir levels by briefly blocking the enzyme that clears it, so avoid amprenavir for 2 weeks after using abametapir, or skip the abametapir. Check with your pharmacist or doctor before combining them. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abametapir and Amprenavir 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 Amprenavir interaction managed?
This interaction is manageable with good planning. Here is what typically happens: Your care team will usually separate these in time. Abametapir's enzyme-slowing effect can last up to 2 weeks after the scalp application, so they may avoid CYP3A4 medicines like amprenavir during that window. If avoiding amprenavir is not possible, the team may instead choose a different lice treatment. Keep taking… 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 Amprenavir 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 Amprenavir
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