Drug Interaction Report

Asenapine Transdermal Patch and Gefitinib: Interaction Details

A pharmacist-reviewed analysis of the Asenapine Transdermal Patch and Gefitinib interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Gefitinib

Iressa Iressa®
+

Asenapine Transdermal Patch

Secuado Secuado®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Jul 11, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
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.

Of 377 documented Asenapine Transdermal Patch interactions, 276 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
unspecified
Evidence
theoretical
Severity
Major

What happens

Increased exposure of CYP2D6 substrate and inhibitor and an increased asenapine exposure

Interaction Deep Dive

Concomitant use of asenapine and a drug that is both a CYP2D6 substrate and inhibitor may result in an increase in exposure of the CYP2D6 substrate and inhibitor and/or asenapine123.

Why it happens (mechanism)

Inhibition of CYP2D6-mediated metabolism by asenapine; inhibition of CYP2D6-mediated metabolism of asenapine

Literature reports

1 report — tap to read

a) Coadministration of asenapine and PARoxetine may increase the Cmax and AUC of PARoxetine approximately by 1.9 fold and 2 fold, respectively 3.

Common questions

Can I take Asenapine Transdermal Patch and Gefitinib together?

Increased exposure of CYP2D6 substrate and inhibitor and an increased asenapine exposure Always confirm with your pharmacist or prescriber before making any change.

How serious is the Asenapine Transdermal Patch and Gefitinib 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 Asenapine Transdermal Patch or Gefitinib 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 (3)

  1. Product Information: SAPHRIS(R) oral sublingual tablets, asenapine oral sublingual tablets. Allergan USA, Inc. (per DailyMed), Madison, NJ, 2021. DailyMed
  2. Product Information: SECUADO® transdermal system, asenapine transdermal system. Noven Therapeutics LLC (per DailyMed), Miami, FL, 2023. DailyMed
  3. Product Information: Asenapine oral sublingual tablets, asenapine oral sublingual tablets. Alembic Pharmaceuticals Ltd (per DailyMed), Bedminster, NJ, 2025. DailyMed
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Beyond drug–drug

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:

Gefitinib + Activated Charcoal Beer Grapefruit Siberian Cocklebur St. John's Wort Wine Acacia Rigidula Adrafinil + 160 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.