Flecainide and Adagrasib: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Adagrasib
Flecainide
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
An increased risk of QT interval prolongation, increased exposure to CYP2D6 substrates
Interaction Deep Dive
Avoid concomitant use of adagrasib with QT prolonging sensitive CYP2D6 substrates. Concomitant use of these drugs will increase the concentrations of these drugs, which may increase the risk of adverse reactions of these drugs and QTc interval prolongation. Concomitant use of adagrasib with other products that prolong the QTc interval may result in a greater increase in the QTc interval and adverse reactions associated with QTc interval prolongation, including torsade de pointes, other serious arrhythmias, and sudden death. Monitor electrocardiogram and electrolytes prior to starting adagrasib, during concomitant use, and as clinically indicated in patients with congestive heart failure, bradyarrhythmias, electrolyte abnormalities, and in patients who are unable to avoid concomitant medications that are known to prolong the QT interval. Withhold adagrasib if the QTc interval is greater than 500 msec or the change from baseline is greater than 60 msec until QTc interval is less than 481 msec or return to baseline. Resume adagrasib at the next lower dose level. Permanently discontinue adagrasib incase of torsade de pointes, polymorphic ventricular tachycardia or signs or symptoms of serious or life-threatening arrhythmia1.
Why it happens (mechanism)
Additive QT interval prolongation; inhibition of CYP2D6 substrate metabolism by adagrasib
Literature reports
1 report — tap to read
a) Concomitant use of 400 mg twice daily dose of adagrasib with dextromethorphan (a sensitive CYP2D6 substrate) increased the AUC and Cmax of dextromethorphan by 1.8-fold and 1.9-fold respectively. With 600 mg twice daily dose of dextromethorphan, the predicted increase in AUC and Cmax of dextromethorphan is by 2.4-fold and 1.7-fold respectively 1.
Common questions
Can I take Flecainide and Adagrasib together?
An increased risk of QT interval prolongation, increased exposure to CYP2D6 substrates Always confirm with your pharmacist or prescriber before making any change.
How serious is the Flecainide and Adagrasib 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 Flecainide or Adagrasib 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: KRAZATI(TM) oral tablets, adagrasib oral tablets. Mirati Therapeutics Inc (per FDA), San Diego, CA, 2024. DailyMed
Keep reading about Adagrasib
Keep reading about Flecainide
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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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