Drug Interaction Report

Allopurinol and Anisindione: Interaction Details

Name: Allopurinol and Anisindione Interaction
Creator: Dr. Brian Staiger, PharmD, BCPS

A pharmacist-reviewed analysis of the Allopurinol and Anisindione interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Allopurinol

Aloprim Lopurin® Zyloprim Zyloprim®

Anisindione

No brand names on record

Medically reviewed by

Dr. Brian Staiger, PharmD, BCPS

Updated Jul 11, 2026

Editorial policy · Data sources

Interaction severity

Moderate

Can be significant — usually manageable with monitoring.

Minor

Moderate

Major

Contraindicated

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.

Of 32 documented Allopurinol interactions, 7 are rated moderate — including this one.

Onset

delayed

Evidence

theoretical

Severity

Moderate

What happens

An increased risk of bleeding

Interaction Deep Dive

Allopurinol may increase the hypoprothrombinemic effect of oral anticoagulants in some patients¹²³.

Why it happens (mechanism)

Decreased anisindione metabolism

Common questions

Can I take Allopurinol and Anisindione together?

An increased risk of bleeding Always confirm with your pharmacist or prescriber before making any change.

How serious is the Allopurinol and Anisindione 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 Allopurinol or Anisindione 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 (3)

Vesell ES, Passananti GT, & Greene FE: Impairment of drug metabolism in man by allopurinol and nortriptyline. N Engl J Med 1970; 283:1484-1488. PubMed
Pond SM, Graham GG, Wade DN, et al: The effects of allopurinol and clofibrate on the elimination of coumarin anticoagulants in man. Aust N Z J Med 1975; 5:324-328. DOI
Jahnchen E, Meinertz I, & Gilfrich HJ: Interaction of allopurinol with phenprocoumon in man. Klin Wochensch 1977; 55:759-761. DOI

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Allopurinol

Keep reading about Allopurinol

All Allopurinol interactions (32) Allopurinol drug information

Also serious with: Fezolinetant Didanosine Acenocoumarol Pegloticase Injection

Anisindione

Keep reading about Anisindione

All Anisindione interactions (43)

Also serious with: Aspirin Aspirin Rectal Danazol Fluoxymesterone

Beyond drug–drug

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:

Allopurinol + Activated Charcoal Asarabacca Beer Siberian Cocklebur Wine Aristolochia Ashwagandha Black Cohosh + 52 more

Anisindione + Activated Charcoal Danshen Piracetam Aconite Allspice Aloe Alpha-lipoic Acid Andrographis + 210 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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A message from HelloPharmacist

About our interaction database: depth, not breadth

HelloPharmacist doesn't license one of the big commercial interaction databases, so what you'll find here is not a complete list of every known drug interaction. Instead, each entry is researched, analyzed, and written up individually — documented from the published literature, reviewed by a pharmacist, and cited so you can check every source yourself.

If a combination isn't listed here, it means we haven't documented it yet — never that it's safe. For screening a full medication list, we recommend pairing this site with a comprehensive tool like the Drugs.com Interaction Checker and, most importantly, a review by your own pharmacist. For a deep, plain-English, fully sourced explanation of a specific documented interaction — that's exactly what we built this for.

This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.