Vincristine 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 recordVincristine
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 can get into your body and briefly slow down a liver enzyme (called CYP3A4) that helps break down many medicines. Vincristine is a chemotherapy drug that your body clears using that same enzyme.
So after using abametapir, vincristine could build up higher than expected. That matters because vincristine's side effects (like nerve tingling, constipation, or weakness) can get worse when levels climb. The good news: this is manageable. Please talk with your oncology team and pharmacist before combining these, and they can plan the safest timing for you.
Mechanism: Abametapir is a CYP3A4 inhibitor. Vincristine is a CYP3A4 substrate (not a prodrug), so inhibition reduces its metabolic clearance and increases systemic exposure (AUC/Cmax).
Direction/effect: Increased vincristine exposure, raising risk of dose-related toxicity (peripheral neuropathy, autonomic effects, myelosuppression).
- Onset: rapid
- Evidence: theoretical, but severity rated major
- Management: Avoid CYP3A4 substrates for 2 weeks after topical abametapir application. If concomitant vincristine is unavoidable, avoid abametapir. Coordinate timing with oncology and monitor for neurotoxicity if exposure occurs.
What happens
Increased exposure of CYP3A4 substrate
Interaction Deep Dive
CYP3A4 substrates should not be used during the 2 weeks following application of abametapir. Should avoiding such use be impractical, abametapir itself should be avoided 1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism by abametapir
How to manage this interaction
The documented guidance here is about timing and avoidance rather than a set dose change.
- Do not start or stop either medication on your own. Vincristine is chemotherapy, so any change must come from your oncology team.
- Because abametapir's enzyme-slowing effect can linger, the recommendation is to avoid CYP3A4 substrates for about 2 weeks after applying abametapir. If vincristine cannot wait, then abametapir should be avoided instead.
- Tell your pharmacist and oncologist you have been prescribed both, so they can plan the safest timing.
- If you do end up on both, your team may monitor you more closely for vincristine side effects like numbness, tingling, or constipation.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Vincristine and Abametapir together?
Abametapir can slow how your body clears vincristine, so levels may rise and side effects worsen. Space them apart (avoid CYP3A4 substrates for about 2 weeks after abametapir) and let your oncology team plan the timing. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Vincristine 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 Vincristine and Abametapir interaction managed?
The documented guidance here is about timing and avoidance rather than a set dose change. Do not start or stop either medication on your own. Vincristine is chemotherapy, so any change must come from your oncology team. Because abametapir's enzyme-slowing effect can linger, the recommendation is to avoid CYP3A4 substrates for about 2 weeks after applying abametapir. If vincristine cannot wait, the… 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 Vincristine 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 Vincristine
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