Drug & supplement interaction

Willow Bark + Sorafenib

Sorafenib brand name: Nexavar.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Willow Bark has a moderate interaction with Sorafenib. Theoretically, willow bark might increase the risk of bleeding when taken with anticoagulant/antiplatelet drugs.

Read the full interaction report
SeverityModerate
LikelihoodProbable
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Willow Bark and Sorafenib

Here is the interaction we found between these two, with the evidence behind it.

Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

Why this applies to Sorafenib

Sorafenib falls under ANTICOAGULANT/ANTIPLATELET DRUGS — the group Willow Bark interacts with.

Theoretically, willow bark might increase the risk of bleeding when taken with anticoagulant/antiplatelet drugs.
Willow bark has antiplatelet effects, but less so than aspirin.
Severity Moderate Likelihood Probable Evidence D

Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thing to keep in mind with willow bark and Sorafenib (Nexavar). Willow bark contains salicin, which your body turns into a salicylic acid that acts a lot like aspirin and can make your blood a little slower to clot. Sorafenib, on its own, already carries a real risk of bleeding as one of its known side effects. Stacking the two together could nudge that bleeding risk a bit higher.

To be fair, this is a theoretical concern based on how these two work, not on strong studies, and willow bark's blood-thinning effect is milder than aspirin's. Still, with a cancer therapy like this, I'd play it safe. Watch for easy bruising, nosebleeds, bleeding gums, or unusual fatigue, and please check with your oncologist or pharmacist before adding willow bark.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Krivoy N, Pavlotzky E, Chrubasik S, et al. Effect of salicis cortex extract on human platelet aggregation. Planta Med 2001;67:209-12. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Willow Bark Also Interacts With Other Medications

Willow Bark has 126 moderate known drug interactions in our database — the Sorafenib one above is one of them. If you take anything else, check it against the full list below.

Moderate 126 No known interaction 2,704 (incl. Sorafenib)
Taking anything else?

Check Another of Your Medications Against Willow Bark

Covers the 2,830 medications we’ve checked against Willow Bark. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Sorafenib

This page covers Willow Bark only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Sorafenib page lists 285 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Danshen (major), Grapefruit (major), Piracetam (major) and St. John's Wort (major).

By severity: 5 major · 241 moderate · 39 minor.

From our pharmacist’s overview on the Sorafenib page

“If you're on sorafenib (Nexavar) for cancer, be genuinely careful here, and learn the five major-rated entries first. Most of the 285 ingredients listed either have blood-thinning effects that stack onto sorafenib's bleeding risk (more than 200 do) or affect CYP3A4, the liver enzyme that clears the drug, pushing its level too high or t…”

Reviewed by 2 · Jul 18, 2026

Open the Sorafenib interaction page

One more smart check

Taking Willow Bark as Part of a Dietary Supplement Product? Check It for Interactions

We hold 43 real supplement products containing Willow Bark, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Willow Bark. Your product may carry other ingredients that interact with Sorafenib too, on top of Willow Bark — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Willow Bark and Sorafenib Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Willow Bark
Steady interest

#1,174 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Sorafenib
Steady interest

#2,507 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Willow Bark

What is Willow Bark?

  • Low back pain
  • Osteoarthritis joint pain
  • Headache
  • Fever
  • General aches and inflammation

Willow bark is a traditional plant remedy that contains salicin, a compound related to aspirin, and is most often used for pain and inflammation. Some evidence suggests it may modestly help low back pain and joint pain, but the research is limited and the right dose is not well standardized. Because it acts like aspirin, people with aspirin allergies, bleeding problems, or who are pregnant should be cautious and talk to a pharmacist or doctor first.

Read the full Willow Bark monograph & all interactions
Medication

About Sorafenib

What Is Sorafenib Used For?

Brand name: Nexavar

Sorafenib tablets are approved to treat three types of cancer. The first is unresectable hepatocellular carcinoma (HCC) — liver cancer that cannot be removed with surgery. The second is advanced renal cell carcinoma (RCC) — kidney cancer that has spread or progressed. Both the brand Nexavar and generic sorafenib tablets are approved for these two uses.

The third use is for locally recurrent or metastatic, progressive differentiated thyroid carcinoma (DTC) — thyroid cancer that has spread or worsened and no longer responds to radioactive iodine treatment. Nexavar and sorafenib tablets are both approved for this use as well.

See full Sorafenib drug information
Keep checking

Other Drugs & Willow Bark

Browse every other medication we’ve checked against Willow Bark — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
126Moderate
0Minor
2,703No known interaction
126 Moderate 2,703 No interaction
Moderate

126 interactions

Showing 60 of 126 moderate interactions — see all 126 on the Willow Bark page.

No interaction 2,703 drugs checked — show the list

We also checked Willow Bark against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,703 medications checked with no known interaction — see the full Willow Bark list.

See the full Willow Bark interactions page
See every supplement checked against Sorafenib, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Willow Bark monograph › Uses, safety, and every drug interaction in one place Sorafenib supplement interactions › Every supplement checked against Sorafenib, ranked by severity Sorafenib drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Willow Bark and Sorafenib Together: Common Questions

Can you take Willow Bark with Sorafenib?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Willow Bark and Sorafenib interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Sorafenib and Willow Bark?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.