Defactinib and Esomeprazole: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Esomeprazole
Defactinib
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.
What happens
Reduced defactinib exposure and an reduced efficacy of defactinib
Interaction Deep Dive
Avoid concomitant use of defactinib with proton pump inhibitors (PPIs) as it may reduce defactinib exposure which may reduce efficacy of defactinib. If concomitant use of an acid-reducing agent cannot be avoided, administer defactinib 2 hours before or 2 hours after the administration of a locally acting antacid. Defactinib displayed pH-dependent aqueous solubility. Defactinib AUC decreased by 79% and Cmax decreased by 85% following concomitant use of multiple doses of omeprazole (PPI) 40 mg daily. M4 AUC decreased by 83% and Cmax decreased by 88%1.
Why it happens (mechanism)
Changes in gastric pH
Literature reports
1 report — tap to read
a) Defactinib displayed pH-dependent aqueous solubility. Defactinib AUC decreased by 79% and Cmax decreased by 85% following concomitant use of multiple doses of omeprazole (PPI) 40 mg daily. Major metabolite of defactinib, N-desmethyl amide (M4) AUC decreased by 83% and Cmax decreased by 88% 1.
Common questions
Can I take Defactinib and Esomeprazole together?
Reduced defactinib exposure and an reduced efficacy of defactinib Always confirm with your pharmacist or prescriber before making any change.
How serious is the Defactinib and Esomeprazole 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 strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Defactinib or Esomeprazole 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: AVMAPKI(TM) FAKZYNJA(TM) CO-PACK oral capsules, tablets, avutometinib oral capsules, defactinib oral tablets. Verastem, Inc (per manufacturer), Needham, MA, 2025. DailyMed
Keep reading about Esomeprazole
Keep reading about Defactinib
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.
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