Interferon Alfa-2A and Captopril: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Captopril
Interferon Alfa-2A
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
Hematologic abnormalities (granulocytopenia, thrombocytopenia)
Interaction Deep Dive
Concurrent use of interferon alpha and captopril has been associated with the development of hematologic abnormalities (granulocytopenia, thrombocytopenia) in some patients1. However, reports of combination therapy without hematologic consequences also exist 2.
Why it happens (mechanism)
Unknown; may involve autoimmune effects on myeloid precursors
Literature reports
2 reports — tap to read
a) Thirty-eight patients were treated with interferon for mixed cryoglobulinemia. Thirty-five patients received recombinant interferon alpha-2a and three patients received natural interferon beta. Except for two patients who received reduced doses, the dosage regimen consisted of interferon 3 million units daily, intramuscularly or subcutaneously, for three months followed by the same dose every other day for another six to 17 months. In 35 patients, there were no significant changes in granulocyte, red blood cell, or platelet counts during the study period. Three patients treated with interferon alpha-2a developed severe granulocytopenia. All three patients were also receiving an ACE inhibitor (captopril or enalapril) for the treatment of hypertension. As no patient experienced hematologic abnormalities while on interferon or an ACE inhibitor alone, the authors concluded that concomitant use of interferon and ACE inhibitors may result in synergistic hematologic toxicity. The postulated mechanism of this effect is thought to involve autoimmune destruction of myeloid precursors 1.
b) Two patients being treated with interferon alpha-2a 3 million units daily or on alternate days and either captopril 75 mg daily or enalapril 20 mg daily experienced a decrease in granulocytes which rebounded back to previous levels without changing drug therapy. Both patients were being treated for type II mixed cryoglobulinemia. Granulocyte counts dropped to 1300 per mm(3) in the captopril-treated patient and 910 per mm(3) in the enalapril-treated patient within nine days of starting interferon therapy. Within two weeks the granulocyte counts returned to normal, even though no change in dosage or drug therapy occurred. Another patient being treated with interferon alpha-2a 3 million units three times weekly for multiple myeloma received benazepril 10 mg daily concurrently. After three months of combined therapy, granulocyte counts were still within the normal range 2.
Common questions
Can I take Interferon Alfa-2A and Captopril together?
Hematologic abnormalities (granulocytopenia, thrombocytopenia) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Interferon Alfa-2A and Captopril 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 Interferon Alfa-2A or Captopril 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 (2)
- Casato M, Pucillo LP, Leoni M, et al: Granulocytopenia after combined therapy with interferon and angiotensin-converting enzyme inhibitor: evidence for a synergistic hematologic toxicity. Am J Med 1995; 99:386-391.
- Jacquot C, Caudwell V, & Belefant X: Granulocytopenia after combined therapy with interferon and angiotensin-converting enzyme inhibitors: evidence for a synergistic hematologic toxicity (letter). Am J Med 1996; 101:235-236. PubMed
Keep reading about Captopril
Keep reading about Interferon Alfa-2A
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist