Peginterferon Alfa-2B and Mexiletine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Mexiletine
Peginterferon Alfa-2B
No brand names on record
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 the CYP1A2 substrate and increased risk for toxicities
Interaction Deep Dive
Coadministration of peginterferon alfa-2b (CYP1A2 inhibitor) with a CYP1A2 substrate may increase exposure of the substrate, potentially resulting in toxicity and increased side effects. When caffeine (CYP1A2 substrate) was given before and after 2 doses of peginterferon alfa-2b in a study, there was an increase in the mean AUC(last) of 36% compared with administration of caffeine alone. If a CYP1A2 substrate with a narrow therapeutic index is coadministered with peginterferon alfa-2b, monitor for potential increased toxicities of the CYP1A2 substrate1.
Why it happens (mechanism)
Inhibition of CYP1A2-mediated metabolism by peginterferon alfa-2b
Literature reports
1 report — tap to read
a) Peginterferon alfa-2b inhibited CYP1A2 activity in a drug interaction study. When healthy subjects were given 200 mg of caffeine (CYP1A2 substrate) before and after 2 doses of peginterferon alfa-2b 3 mcg/kg (CYP1A2 inhibitor), there was an increase in the mean AUC(last) of 36% compared with administration of caffeine alone 1.
Common questions
Can I take Peginterferon Alfa-2B and Mexiletine together?
Increased exposure of the CYP1A2 substrate and increased risk for toxicities Always confirm with your pharmacist or prescriber before making any change.
How serious is the Peginterferon Alfa-2B and Mexiletine 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 Peginterferon Alfa-2B or Mexiletine 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: SYLATRON(TM) subcutaneous injection, peginterferon alfa-2b subcutaneous injection. Merck Sharp & Dohme Corp. (per FDA), Whitehouse Station, NJ, 2017.
Keep reading about Mexiletine
Keep reading about Peginterferon Alfa-2B
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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