Peginterferon Alfa-2A Injection and Methadone: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 9, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Methadone
Peginterferon Alfa-2A Injection
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 methadone concentrations
Interaction Deep Dive
Caution should be used when coadministering methadone and peginterferon alfa-2a as it may result in increased methadone levels and a greater risk for methadone side effects. Monitor for signs and symptoms of methadone toxicity1.
Why it happens (mechanism)
Unknown
Literature reports
1 report — tap to read
a) After 4 weeks of concomitant treatment with methadone and peginterferon alfa-2a, methadone pharmacokinetic (PK) parameters were 10% to 15% higher in 24 peginterferon alfa-2a naive chronic hepatitis C patients receiving 180 mcg of peginterferon alfa-2a weekly. Prior to starting peginterferon, all patients were on median stable methadone dose of 95 mg (30 mg to 150 mg). There were no significant changes in the PK parameters of peginterferon alfa-2a when compared with 6 patients not receiving methadone 1.
Common questions
Can I take Peginterferon Alfa-2A Injection and Methadone together?
Increased methadone concentrations Always confirm with your pharmacist or prescriber before making any change.
How serious is the Peginterferon Alfa-2A Injection and Methadone interaction?
It is rated moderate. Can be significant — usually manageable with 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 "established". Well documented — supported by controlled studies or strong clinical data.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Peginterferon Alfa-2A Injection or Methadone 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 anything you'd monitor while I'm on both?
References (1)
- Product Information: PEGASYS(R) subcutaneous injection solution, peginterferon alfa-2a subcutaneous injection solution. Genentech USA, Inc. South San Francisco, CA, 2011. DailyMed
Keep reading about Methadone
Keep reading about Peginterferon Alfa-2A Injection
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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