Theophylline and Peginterferon Alfa-2A Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 9, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Peginterferon Alfa-2A Injection
Theophylline
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
Theophylline toxicity (nausea, vomiting, palpitations, seizures)
Interaction Deep Dive
Treatment with peginterferon alfa-2a once weekly for four weeks in healthy subjects was associated with an inhibition of cytochrome P450 1A2 and a 25% increase in theophylline area under the concentration-time curve1.
Why it happens (mechanism)
Unknown
Common questions
Can I take Theophylline and Peginterferon Alfa-2A Injection together?
Theophylline toxicity (nausea, vomiting, palpitations, seizures) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Theophylline and Peginterferon Alfa-2A Injection interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Theophylline or Peginterferon Alfa-2A Injection 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: Pegasys(R), peginterferon alfa-2a. Hoffmann-La Roche Inc. Nutley, New Jersey, 2002. DailyMed
Keep reading about Peginterferon Alfa-2A Injection
Keep reading about Theophylline
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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