Dacomitinib and Atomoxetine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Atomoxetine
Dacomitinib
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 atomoxetine exposure and an increased risk of atomoxetine-related adverse reactions
Interaction Deep Dive
Coadministration of atomoxetine and strong CYP2D6 inhibitors may increase atomoxetine exposure. Administer atomoxetine once daily in the morning or divided doses (morning and late afternoon/early evening): Dosing for adults and pediatric patients more than or equal to 6 years: a titration interval of every 4 weeks if symptoms persist and the dose is well tolerated. For pediatric patients less than 70 kg: Start at 0.5 mg/kg/day, titrate to 1.2 mg/kg/day. No additional benefit above 1.2 mg/kg/day. For pediatrics more than or equal to 70 kg and adults: Start at 40 mg/day, titrate to 80 mg/day. Dosing for other CYP2D6 metabolizer types (Ultrarapid, Normal, Intermediate), use standard dosing with a minimum titration interval of 3 days. For pediatrics less than 70 kg: Start at 0.5 mg/kg/day, titrate to 1.2 mg/kg/day, to a maximum of 1.4 mg/kg/day. For pediatric patients more than or equal to 70 kg and adults: Start at 40 mg/day, titrate to 80 mg/day, to a maximum of 100 mg/day. No added benefit above 1.2 mg/kg/day; If response is inadequate at 80 mg/day after 2-4 weeks, the dose may be increased to 100 mg/day, and no evidence supports efficacy above 100 mg/day1.
Why it happens (mechanism)
Inhibition of CYP2D6-mediated metabolism of atomoxetine
Literature reports
1 report — tap to read
a) In a drug interaction study, concomitant use of another atomoxetine product (ie, atomoxetine capsules) (20 mg twice daily for 5 days) with PARoxetine (20 mg once daily for 17 days), a known inhibitor of CYP2D6, in subjects who were not CYP2D6 poor metabolizers resulted in a 6.5-fold higher plasma exposure (AUC) to atomoxetine at steady state. In another drug interaction study, concomitant use of the other atomoxetine product (at sequential dosing of 10, 45, and 75 mg twice daily for up to 5 days of each dosage) with FLUoxetine (20 mg once daily for 36 days) a known inhibitor of CYP2D6, in subjects who were not CYP2D6 poor metabolizers resulted in 6- to 8-fold increases of plasma atomoxetine exposure (AUC) at steady state compared to taking the other atomoxetine product alone 1.
Common questions
Can I take Dacomitinib and Atomoxetine together?
Increased atomoxetine exposure and an increased risk of atomoxetine-related adverse reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Dacomitinib and Atomoxetine 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Dacomitinib or Atomoxetine 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: ATONCY™ oral solution, atomoxetine oral solution. Validus Pharmaceuticals LLC (Per FDA), Parsippany, NJ, 2026. DailyMed
Keep reading about Atomoxetine
Keep reading about Dacomitinib
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