Abametapir and Erythromycin: 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 recordErythromycin
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 gets into your body and can slow down a liver enzyme (called CYP3A4) that helps break down many medicines, including the antibiotic erythromycin.
Because that enzyme is slowed, erythromycin could build up higher than usual for a while. That may raise the chance of side effects like stomach upset or, less commonly, heart rhythm changes. This effect is based on how the drugs work rather than on reported cases, so it's a precaution. The good news is your care team can easily manage this by adjusting the timing of your medicines. Please check with your pharmacist or doctor before using both.
Mechanism: Abametapir inhibits CYP3A4, reducing metabolism of CYP3A4 substrates. Erythromycin is a CYP3A4 substrate (and itself a CYP3A4 inhibitor), so co-exposure can increase erythromycin AUC/Cmax.
Direction: Increased erythromycin exposure, potentially raising risk of GI effects and QT prolongation. Neither agent is a relevant prodrug here.
- Onset: rapid
- Evidence: theoretical (based on mechanism/labeling, not case data)
- Severity: major
Management: Avoid CYP3A4 substrates, including erythromycin, for 2 weeks after topical abametapir. If the substrate cannot be avoided, avoid abametapir. Individualize timing with the care team.
What happens
Increased exposure of CYP3A4 substrate
Interaction Deep Dive
During the 2 weeks following abametapir application, substrates of CYP3A4 should not be used. When avoiding such substrates is not possible, then abametapir itself should be avoided 1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism by abametapir
How to manage this interaction
Both drugs can be used safely with a little planning. Because abametapir can slow the enzyme that clears erythromycin for up to 2 weeks after you apply it, your care team's usual approach is about timing and choice, not stopping treatment on your own.
- Tell your pharmacist or prescriber that you use (or plan to use) both.
- Your team may space out the two, avoiding erythromycin for about 2 weeks after the lice lotion, or choose a different option for one of them.
- Keep taking any medicine exactly as prescribed unless your provider tells you otherwise.
- Report new stomach upset, palpitations, or feeling faint.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Abametapir and Erythromycin together?
Abametapir can raise erythromycin levels for up to 2 weeks by slowing its breakdown, so let your pharmacist or doctor separate or substitute them rather than combining them right after the lice treatment. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abametapir and Erythromycin 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 Erythromycin interaction managed?
Both drugs can be used safely with a little planning. Because abametapir can slow the enzyme that clears erythromycin for up to 2 weeks after you apply it, your care team's usual approach is about timing and choice, not stopping treatment on your own. Tell your pharmacist or prescriber that you use (or plan to use) both. Your team may space out the two, avoiding erythromycin for about 2 weeks afte… 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 Erythromycin 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 Erythromycin
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major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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