Hydralazine and Indomethacin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Indomethacin
Hydralazine
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
Decreased hydrALAZINE effectiveness
Interaction Deep Dive
Oral doses of indomethacin may attenuate the antihypertensive effects of intravenous hydrALAZINE21.
Why it happens (mechanism)
Antagonism
Literature reports
2 reports — tap to read
a) A placebo-controlled study in 9 healthy adult volunteers was conducted to evaluate the effects of indomethacin on the vasodilator action of hydrALAZINE 1. Subjects were given either oral indomethacin (200 mg) or a placebo, then they received two 0.15 mg/kg doses of intravenous hydrALAZINE 30 minutes apart. The administration of indomethacin resulted in no hypotensive response with the first dose of hydrALAZINE and a decrease in the hypotensive response observed with the second dose compared to the placebo. Indomethacin administration had no effect on heart rate, renal blood flow, limb blood flow, and plasma catecholamine levels when compared to the placebo. The decrease in hypotensive response observed in this short-term study may indicate that prostaglandins play a role in hydrALAZINE-induced vasodilation, at least acutely. Whether or not this effect is observed with long-term therapy needs to be determined. Until then, patients receiving hydrALAZINE therapy who are started on indomethacin therapy should be observed for changes in blood pressure control.
b) Administration of an IV injection of 0.2 mg/kg hydrALAZINE to healthy volunteers who had received indomethacin 100 mg PO daily for 2.5 days resulted in no interference of the hypotensive effect of hydrALAZINE 2. More studies are required in hypertensive patients to confirm lack of an interaction.
Common questions
Can I take Hydralazine and Indomethacin together?
Decreased hydrALAZINE effectiveness Always confirm with your pharmacist or prescriber before making any change.
How serious is the Hydralazine and Indomethacin interaction?
It is rated moderate. Can be significant — usually manageable with 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Hydralazine or Indomethacin 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 (2)
Keep reading about Indomethacin
Keep reading about Hydralazine
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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