Captopril and Azathioprine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Azathioprine
Captopril
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 myelosuppression and an increased risk of hepatotoxicity
Interaction Deep Dive
The use of captopril to control hypertension in patients receiving azaTHIOprine has induced severe anemia2 or leukopenia 35. Mercaptopurine is hepatotoxic. Hepatotoxicity may be increased when mercaptopurine is coadministered with other products that can cause hepatoxicity, such as captopril. There are reports of deaths attributed to hepatic necrosis associated with the administration of mercaptopurine. Hepatic injury can occur with any dosage but seems to occur with greater frequency when the recommended dosage is exceeded. Monitor serum transaminase levels, alkaline phosphatase, and bilirubin levels at weekly intervals when first beginning therapy and at monthly intervals thereafter. Monitor liver tests more frequently in patients who are receiving mercaptopurine with other hepatotoxic drugs or with known pre-existing liver disease. Withhold mercaptopurine at onset of hepatotoxicity 1.
Why it happens (mechanism)
Additive hepatotoxic effects
Literature reports
4 reports — tap to read
a) Eleven renal transplant patients who had been converted from cycloSPORINE and predniSONE to azaTHIOprine and predniSONE and were concurrently taking either captopril or enalapril developed severe anemia. When two of these patients were converted back to cycloSPORINE, their anemia rapidly resolved. In order to study the effect of concurrent use of azaTHIOprine and either enalapril or captopril, two groups of 10azaTHIOprine-treated patients who did (group A) or did not (group B) take an ACE inhibitor were compared to determine hematological parameters. In group A, 8 patients received enalapril and 2 received captopril. Hematocrit (32.9 +/- 6.3% vs 41.0 +/- 5%), hemoglobin (11.5 +/- 2 g/dL vs 13.9 +/- 1.6 g/dL), and haptoglobin (115.7 +/- 65.4 vs 210.4 +/- 114.4 mg/dL) values of group A were significantly lower than those of group B. Hematological parameters and renal function were compared in group A for the periods 3 to 6 months before and 3 to 6 months after institution of ACE inhibitor therapy. There was a significant decrease in hematocrit (mean 41.5% vs 36%) and hemoglobin (mean 14.1% vs 11.3%) 3 to 6 months after starting ACE inhibitor therapy. Other hematological parameters and renal function remained stable 2.
b) A 17-year-old female with malignant nephrosclerosis was being successfully treated with captopril 50 mg daily and furosemide 500 mg daily for seven months. White cell counts were within the normal range. The patient then received a renal transplant, and 20 days after the addition of azaTHIOprine 150 mg daily to the captopril therapy, the white cell count fell to 1700/mcgL. azaTHIOprine was stopped and the white count returned to normal (4600/mcgL) within eight days. When AzaTHIOprine was reintroduced because of suspected rejection, the white count again fell to 2300/mcgL over 16 days. Captopril therapy was discontinued and blood pressure was controlled by other antihypertensive medications. The patient's white count returned to normal within five days (4700/mcgL), despite continuing azaTHIOprine therapy 3.
c) A 37-year-old renal transplant patient developed anemia while being treated with azaTHIOprine and enalapril, despite also receiving recombinant human erythropoietin (rHuEpo). Three months post-transplant, enalapril 10 mg daily was added to the patient's regimen, which included cycloSPORINE, azaTHIOprine, mizoribine, and prednisoLONE. Normocytic normochromic anemia gradually appeared, and 6000 International Units per week of rHuEpo was administered intravenously when the hematocrit (Hct) dropped from 38.7% to 21%. In spite of the rHuEpo dose being increased to 9000 International Units, the anemia continued to worsen. The patient had no evidence of decreasing renal function, leukopenia, or thrombocytopenia. When the Hct dropped to 16.5%, the enalapril was discontinued. The Hct gradually recovered to 32.2%, even though the rHuEpo administration had been stopped 4.
d) The use of captopril to control hypertension in patients receiving azaTHIOprine has induced severe anemia or leukopenia 5.
Common questions
Can I take Captopril and Azathioprine together?
An increased risk of myelosuppression and an increased risk of hepatotoxicity Always confirm with your pharmacist or prescriber before making any change.
How serious is the Captopril and Azathioprine 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 "established". Well documented — supported by controlled studies or strong clinical data.
Questions for your pharmacist
- Does my dose of Captopril or Azathioprine 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 (5)
- Product Information: PURIXAN(R) oral suspension, mercaptopurine oral suspension. Rare Disease Therapeutics Inc (per FDA), Franklin, TN, 2024. DailyMed
- Gossmann J, Kachel HG, Schoeppe W, et al: Anemia in renal transplant recipients caused by concomitant therapy with azathioprine and angiotensin-converting enzyme inhibitors. Transplantation 1993; 56:585-589. PubMed
- Kirchertz EJ, Grone HJ, Rieger J, et al: Successful low dose captopril rechallenge following drug-induced leucopenia (letter). Lancet 1981; 1:1362-1363. DOI
- Kuriyama R, Hogure H, Itoh S, et al: Angiotensin converting enzyme inhibitor induced anemia in a kidney transplant recipient. Transplant Proc 1996; 28:1635.
- Product Information: Imuran(R), azathioprine. Glaxo Wellcome Inc. Research Triangle Park, NC, 1995. DailyMed
Keep reading about Azathioprine
Keep reading about Captopril
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