Selumetinib and Lenacapavir Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Selumetinib
Lenacapavir Injection
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
Increased selumetinib exposure and an increased risk of selumetinib-related adverse reactions
Interaction Deep Dive
Avoid coadministration of selumetinib with a strong or moderate CYP3A4 inhibitors, as it may increase selumetinib exposure. For selumetinib capsules, if the concurrent dosage is 25 mg/m(2) twice daily, reduce to 20 mg/m(2) twice daily; if the concurrent dosage is 20 mg/m(2) twice daily, reduce to 15 mg/m(2) twice daily. For selumetinib oral granules, if the concurrent dosage is 25 mg/m(2) twice daily, reduce to 20 mg/(2) twice daily; if the concurrent dosage is: 20 mg/m(2) twice daily, reduce to 15 mg/m(2) twice daily. After discontinuation of the strong or moderate inhibitor for 3 elimination half-lives, resume the selumetinib dose that was taken prior to coadministration. In a drug interaction study, concomitant use of itraconazole (strong CYP3A4 inhibitor) increased selumetinib AUC by 49% and Cmax by 19% in a clinical study. Coadministration with erythromycin (moderate CYP3A4 inhibitor) is predicted to increase selumetinib AUC by 41% and Cmax by 23%. In another drug interaction study, concomitant use of fluconazole (strong CYP2C19 and moderate CYP3A4 inhibitor) increased selumetinib AUC by 53% and Cmax by 26%1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of selumetinib
Literature reports
2 reports — tap to read
a) In a drug interaction study, concomitant use of itraconazole (strong CYP3A4 inhibitor) increased selumetinib AUC by 49% and Cmax by 19% in a clinical study. Coadministration with erythromycin (moderate CYP3A4 inhibitor) is predicted to increase selumetinib AUC by 41% and Cmax by 23% 1.
b) In another drug interaction study, concomitant use of fluconazole (moderate CYP3A4 inhibitor) increased selumetinib AUC by 53% and Cmax by 26% 1.
Common questions
Can I take Selumetinib and Lenacapavir Injection together?
Increased selumetinib exposure and an increased risk of selumetinib-related adverse reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Selumetinib and Lenacapavir Injection 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Selumetinib or Lenacapavir Injection 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: KOSELUGO® oral capsules, oral granules, selumetinib oral capsules, oral granules. AstraZeneca Pharmaceuticals LP (per Manufacturer), Wilmington, DE, 2025. DailyMed
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