Captopril and Allopurinol Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Captopril
Allopurinol 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
Hypersensitivity reactions (Stevens-Johnson syndrome, skin eruptions)
Interaction Deep Dive
In two case reports, hypersensitivity reactions occurred when captopril and allopurinol were administered concurrently. Both patients had renal dysfunction and were also receiving diuretics12. The use of allopurinol with diuretics or in the presence of renal dysfunction is also associated with hypersensitivity reactions 3. Monitor carefully for hypersensitivity reactions when allopurinol and captopril are administered together.
Why it happens (mechanism)
Unknown
Common questions
Can I take Captopril and Allopurinol Injection together?
Hypersensitivity reactions (Stevens-Johnson syndrome, skin eruptions) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Captopril and Allopurinol 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 Captopril or Allopurinol 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 (3)
- Samanta A & Burden AC: Fever, myalgia, and arthralgia in a patient on captopril and allopurinol (letter). Lancet 1984; 1:679. PubMed
- Pennell DJ, Nunan TO, & O'Doherty MJ: Fatal Stevens-Johnson syndrome in a patient on captopril and allopurinol (letter). Lancet 1984; 1:463. DOI
- Al-Kawas FH, Seeff LB, Berendson RA, et al: Allopurinol hepatotoxicity: report of two cases and review of the literature. Ann Intern Med 1981; 95:588-590. PubMed
Keep reading about Captopril
Keep reading about Allopurinol 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.
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