Fosnetupitant and Abametapir: 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 recordFosnetupitant
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.
Here's what's going on. Abametapir is a lotion used to treat head lice. Even though you put it on your scalp, it can briefly block a liver enzyme called CYP3A4 that your body uses to break down many medicines. Fosnetupitant is one of those medicines (it's given to help prevent nausea and vomiting from chemotherapy).
When that enzyme is slowed down, fosnetupitant can build up more than expected, which could mean stronger effects or more side effects. This is a predicted concern based on how the drugs work, not something seen often in practice. The good news is your care team can easily plan around the timing, so please talk with your pharmacist or doctor before using both.
Mechanism: Abametapir is a topical CYP3A4 inhibitor. Fosnetupitant (a CYP3A4 substrate) may accumulate, increasing systemic exposure (AUC/Cmax).
- Direction: increased fosnetupitant exposure and potential enhanced/adverse effects.
- Onset: rapid; inhibition can persist, so effect may last up to ~2 weeks post-application.
- Evidence: theoretical (based on abametapir's known CYP3A4 inhibition).
- Management: Avoid CYP3A4 substrates, including fosnetupitant, within 2 weeks after applying abametapir. If a CYP3A4 substrate cannot be avoided, avoid using abametapir. Coordinate timing and monitor for exaggerated substrate effects if co-use is unavoidable.
What happens
Increased exposure of CYP3A4 substrate
Interaction Deep Dive
For a period of 2 weeks following abametapir application, refrain from administering CYP3A4 substrates. Should this not be possible, do not use abametapir1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism by abametapir
How to manage this interaction
The main strategy here is timing and avoidance. Because abametapir can slow the enzyme that clears fosnetupitant for a while after you use it, the recommended approach is to keep the two apart.
- Avoid starting fosnetupitant (or other CYP3A4 medicines) within 2 weeks after applying abametapir lotion.
- If you truly need fosnetupitant during that window, the alternative is to avoid using abametapir instead.
- Keep taking any medicine exactly as prescribed, and do not stop anything on your own.
Tell your pharmacist and prescriber that you have used or plan to use abametapir so they can time your treatments safely and watch you more closely if needed.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Fosnetupitant and Abametapir together?
Abametapir can raise fosnetupitant levels by blocking CYP3A4, so avoid fosnetupitant for 2 weeks after applying abametapir, and check with your pharmacist or doctor before combining them. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Fosnetupitant and Abametapir 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 Fosnetupitant and Abametapir interaction managed?
The main strategy here is timing and avoidance. Because abametapir can slow the enzyme that clears fosnetupitant for a while after you use it, the recommended approach is to keep the two apart. Avoid starting fosnetupitant (or other CYP3A4 medicines) within 2 weeks after applying abametapir lotion. If you truly need fosnetupitant during that window, the alternative is to avoid using abametapir ins… 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 Fosnetupitant or Abametapir 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 Fosnetupitant
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist