Abametapir and Pirfenidone: 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 recordPirfenidone
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. Pirfenidone (Esbriet) is a pill for a lung condition called pulmonary fibrosis. Even though abametapir goes on your scalp, some of it can get into your body and block a liver enzyme called CYP1A2. That enzyme is one of the main ways your body clears pirfenidone.
When that enzyme is slowed down, pirfenidone can build up more than expected, which can raise the chance of side effects like nausea, stomach upset, tiredness, or sun sensitivity. This effect can linger for up to two weeks after the lice treatment. The good news is your care team can plan around this easily, so let your pharmacist or doctor know you use both.
Mechanism: Abametapir inhibits CYP1A2. Pirfenidone is a CYP1A2 substrate (neither drug is a prodrug), so inhibition reduces its clearance and increases exposure (AUC/Cmax), potentially amplifying dose-related adverse effects (GI upset, hepatotoxicity, photosensitivity, fatigue).
- Direction: increased pirfenidone exposure and effect.
- Severity: major; evidence: theoretical.
- Onset: unspecified; inhibition may persist up to 2 weeks post-application.
Management: Avoid CYP1A2 substrates such as pirfenidone within 2 weeks after abametapir application. If concurrent use is unavoidable, avoid abametapir and select an alternative lice treatment. If exposure occurs, monitor for pirfenidone toxicity.
What happens
Increased exposure of CYP1A2 substrates
Interaction Deep Dive
Refrain from administering CYP1A2 substrates during the 2 week period following the use of abametapir. When avoiding these substrates is not practical, abametapir itself should not be used 1.
Why it happens (mechanism)
Inhibition of CYP1A2-mediated metabolism by abametapir
How to manage this interaction
This one is usually handled by timing and choosing the right product, not by adjusting your pirfenidone dose yourself.
- Keep taking your pirfenidone (Esbriet) as prescribed. Do not stop or change it on your own.
- Tell your pharmacist or prescriber before using abametapir for lice. Because its enzyme-blocking effect can last about two weeks, the usual advice is to avoid it during that window.
- Ask about an alternative lice treatment that does not interact.
- If both were somehow used together, watch for increased pirfenidone side effects (nausea, stomach upset, unusual tiredness, sunburn easily) and report them.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Abametapir and Pirfenidone together?
Abametapir can raise pirfenidone levels by blocking the enzyme that clears it, so avoid using pirfenidone (and other CYP1A2 drugs) for about two weeks after an abametapir lice treatment, or use a different lice product. Check with your pharmacist before combining them. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abametapir and Pirfenidone 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 Pirfenidone interaction managed?
This one is usually handled by timing and choosing the right product, not by adjusting your pirfenidone dose yourself. Keep taking your pirfenidone (Esbriet) as prescribed. Do not stop or change it on your own. Tell your pharmacist or prescriber before using abametapir for lice. Because its enzyme-blocking effect can last about two weeks, the usual advice is to avoid it during that window. Ask abo… 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 Pirfenidone 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 Pirfenidone
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