Drug Interaction Report

Bladderwrack and Defibrotide Injection: Interaction Details

A pharmacist-reviewed analysis of the Bladderwrack and Defibrotide Injection 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

Defibrotide Injection

Defitelio Defitelio®
+

Bladderwrack

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 16 documented Bladderwrack interactions, 16 are rated moderate — including this one.
Onset
delayed
Evidence
theoretical
Severity
Moderate

What happens

Increased risk of bleeding

Interaction Deep Dive

Theoretically, bladderwrack may potentiate the effects of anticoagulants215364. The fucoidan constituent of bladderwrack may have antithrombin activity similar to that of heparin 6. Caution is advised.

Why it happens (mechanism)

Additive antiplatelet effects

Literature reports

3 reports — tap to read

a) Bladderwrack contains fucoidan, a glucose polymer laminarin, with 40% to 50% of the anticoagulant activity of heparin 234.

b) Fucoidan and its subfractions prolonged activated partial thromboplastin time (aPTT) in human platelet-rich plasma. Higher molecular weight fractions exhibited greater anticoagulant effect 5.

c) The anticoagulant activity of heparin was approximately 12 times greater than that of fucoidan. Increasing amounts of fucoidan resulted in prolonged activated partial thromboplastin time. Fucoidan accelerated the rate of thrombin inhibition when added to heparin cofactor II-thrombin 6.

Common questions

Can I take Bladderwrack and Defibrotide Injection together?

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

How serious is the Bladderwrack and Defibrotide Injection 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 Bladderwrack or Defibrotide 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 anything you'd monitor while I'm on both?

References (6)

  1. Norred CL & Brinker F: Potential coagulation effects of preoperative complementary and alternative medicines. Alt Ther 2001; 7(6):58-67.
  2. Kowalak JF & Mills EJKowalak JF & Mills EJ (Eds): Professional Guide to Complementary & Alternative Therapies, Springhouse Corp. Bethlehem Pike, PA, 2001.
  3. Newall CA, Anderson LA, & Phillipson JDNewall CA, Anderson LA, & Phillipson JD: Herbal Medicines: A Guide for Healthcare Professionals, The Pharmaceutical Press, London, England, 1996.
  4. Usui T, Asari K, & Mizuno T: Isolation of highly purified "fucoidan" from Eisenia bicyclis and its anticoagulant and antitumor activities. Agric Biol Chem 1980; 44:1965-1966.
  5. Durig J, Bruhn T, Zurbon KH, et al: Anticoagulant fucoidan fractions from Fucus vesiculosis induce platelet activation in vitro. Thromb Res 1997; 85:479-491.
  6. Church FC, Meade JB, Treanor RE, et al: Antithrombin activity of fucoidan. J Biol Chem 1989; 264:3618-3623. DOI
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