Afatinib and Quinidine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Afatinib
Quinidine
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 exposure of afatinib
Interaction Deep Dive
Concurrent use of afatinib, a P-glycoprotein (P-gp) substrate, and a P-gp inhibitor may increase afatinib exposure and increase the risk of afatinib adverse effects. When coadministration of afatinib with ritonavir 200 mg twice daily for 3 days (a P-gp inhibitor) was evaluated in healthy volunteers, afatinib AUC and Cmax increased by 19% and 4%, respectively; when ritonavir was administered 1 hour before a single afatinib 20-mg dose, afatinib AUC and Cmax increased by 48% and 39%, respectively; when ritonavir was administered 6 hours after afatinib, the afatinib AUC and Cmax increased by 11% and 5%, respectively. Therefore, if coadministration of afatinib and a P-gp inhibitor is necessary and not tolerated, decrease the afatinib daily dose by 10 mg. Resume the original afatinib dose, as tolerated, if concurrent P-gp inhibitor therapy is discontinued1.
Why it happens (mechanism)
Inhibition of P-glycoprotein-mediated efflux transport of afatinib
Literature reports
1 report — tap to read
a) The concurrent use of ritonavir and afatinib resulted in increased afatinib exposure in 2 pharmacokinetic studies in healthy subjects, with varied amount of elevation dependent upon the timing of dosing of the individual agents. Compared with oral administration of afatinib alone, coadministration of ritonavir 200 mg twice daily for 3 days resulted in increased afatinib AUC(0 to infinity) and Cmax by 19% and 4%, respectively, and when ritonavir administration time was moved to 6 hours after afatinib, the afatinib AUC(0 to infinity) and Cmax increased by 11% and 5%, respectively. In the second study, when ritonavir (200 mg twice daily for 3 days) was administered 1 hour before a single afatinib 20-mg dose, afatinib AUC(0 to infinity) and Cmax increased by 48% and 39%, respectively 1.
Common questions
Can I take Afatinib and Quinidine together?
Increased exposure of afatinib Always confirm with your pharmacist or prescriber before making any change.
How serious is the Afatinib and Quinidine 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 Afatinib or Quinidine 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: GILOTRIF(TM) oral tablets, afatinib oral tablets. Boehringer Ingelheim Pharmaceuticals, Inc. (per FDA), Ridgefield, CT, 2013. DailyMed
Keep reading about Afatinib
Keep reading about Quinidine
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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