Drug Interaction Report

Phenprocoumon and Cholestyramine Resin: Interaction Details

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

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Cholestyramine Resin

Locholest® Locholest® Light Prevalite Prevalite® Questran Questran® Questran® Light
+

Phenprocoumon

No brand names on record
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Moderate
Can be significant — usually manageable with monitoring.
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 97 documented Phenprocoumon interactions, 25 are rated moderate — including this one.
Onset
delayed
Evidence
probable
Severity
Moderate

What happens

Decreased effects of phenprocoumon

Interaction Deep Dive

Cholestyramine can bind oral anticoagulants in the gut and limit their absorption, thus impairing their activity. Separating the doses of the drugs by several hours may lessen the impact of this interaction but since phenprocoumon undergoes enterohepatic recirculation, time separation of the doses will not eliminate the problem21.

Why it happens (mechanism)

Decreased phenprocoumon absorption

Literature reports

1 report — tap to read

a) Cholestyramine 4 g TID given orally doubles the total clearance of phenprocoumon. When phenprocoumon is given intravenously, the elimination is increased by cholestyramine due to an interruption in the enterohepatic circulation of the drug 3. This phenomenon was used therapeutically in a case of suicidal overdose with phenprocoumon. The half-life of phenprocoumon was reduced from 6.8 days to 3.5 days during the administration of cholestyramine 4 g three times daily for 10 days 1.

Common questions

Can I take Phenprocoumon and Cholestyramine Resin together?

Decreased effects of phenprocoumon Always confirm with your pharmacist or prescriber before making any change.

How serious is the Phenprocoumon and Cholestyramine Resin 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 "probable". Good supporting evidence, though not definitively proven.

Questions for your pharmacist

  • Does my dose of Phenprocoumon or Cholestyramine Resin 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)

  1. Meinertz T, Gilfrich MJ, Groth U, et al: Interruption of the enterohepatic circulation of phenprocoumon by cholestyramine. Clin Pharmacol Ther 1977a; 21:731-735. PubMed
  2. Jahnchen E, Meinertz T, Gilfrich HJ, et al: Enhanced elimination of warfarin during treatment with cholestyramine. Br J Clin Pharmacol 1978; 5:437-440. DOI
  3. Meinertz T, Gilfrich MJ, Bork R, et al: Treatment of phenprocoumon intoxication with cholestyramine. Br Med J 1977; 2:439. PubMed
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Cholestyramine Resin

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All Cholestyramine Resin interactions (70) Cholestyramine Resin drug information
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Phenprocoumon

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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:

Phenprocoumon + Activated Charcoal Danshen Piracetam St. John's Wort Aconite Allspice Aloe Alpha-lipoic Acid + 211 more

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

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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.