Quinidine and Aspirin Rectal: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Aspirin Rectal
Quinidine
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
Prolonged bleeding times
Interaction Deep Dive
Both aspirin and quinidine disrupt platelet aggregation, and when used in combination appear to have additive effects1.
Why it happens (mechanism)
Additive antiplatelet effects
Literature reports
1 report — tap to read
a) A case report of a prolonged bleeding time secondary to aspirin plus quinidine therapy in a 67-year-old patient is presented by 1. While receiving quinidine 800 mg daily and aspirin 325 mg twice daily, petechiae and melena occurred. Platelet count was normal at 397,000, but the bleeding time was greater than 35 minutes. Two weeks after discontinuation of aspirin, the bleeding time was still prolonged at 15 minutes. Ten days after discontinuation of quinidine, the bleeding time decreased to 9 minutes. Platelet counts were normal throughout this time period. In two normal volunteers, five days of quinidine (975 mg daily) alone or aspirin (650 mg three times daily) alone prolonged bleeding times by 163% and 125%, respectively. The combination resulted in a 288% prolongation. In an in vitro study, both aspirin and quinidine were shown to inhibit epinephrine-induced platelet aggregation by altering the alpha-2-adrenergic receptor on the platelet.
Common questions
Can I take Quinidine and Aspirin Rectal together?
Prolonged bleeding times Always confirm with your pharmacist or prescriber before making any change.
How serious is the Quinidine and Aspirin Rectal 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.
Questions for your pharmacist
- Does my dose of Quinidine or Aspirin Rectal 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 (1)
- Lawson D, Mehta, Mehda P, et al: Culmulative effects of quinidine and aspirin on bleeding time and platelet alpha-2-adrenoreceptors: potential mechanism of bleeding diathesis in patients receiving this combination. J Lab Clin Med 1986; 108:581-586.
Keep reading about Aspirin Rectal
Keep reading about Quinidine
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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