Drug & supplement interaction

Willow Bark + Aspirin, Methocarbamol

Aspirin, Methocarbamol brand name: Robaxisal.

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

Aspirin, Methocarbamol falls into 2 drug categories that Willow Bark can interact with; the most serious is rated moderate. Theoretically, willow bark might increase the risk of bleeding when taken with anticoagulant/antiplatelet drugs.

Read the full interaction report
SeverityModerate
LikelihoodProbable
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Willow Bark and Aspirin, Methocarbamol

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Willow Bark interacts with whole categories of medication. Aspirin, Methocarbamol falls into 2 of those categories, so it can interact with Willow Bark in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

1 of 2

Why this applies to Aspirin, Methocarbamol

Aspirin, Methocarbamol 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 key thing about Robaxisal: it already contains aspirin, which thins the blood by making platelets less sticky. Willow bark works in a very similar way because your body turns its salicin into salicylic acid, the same family of chemical as aspirin. So you'd essentially be stacking two aspirin-like blood thinners on top of each other.

In theory, that doubling up could nudge your bleeding risk higher. Think easy bruising, nosebleeds, bleeding gums, or stomach upset and ulcers from the aspirin. This is rated as a theoretical concern based on how these compounds behave, and willow bark is a milder blood thinner than aspirin, so it's not a reason to panic. Still, please check with your pharmacist or doctor before combining them.

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
Moderate

ASPIRIN

2 of 2
Theoretically, willow bark might increase the effects and adverse effects of aspirin.
Willow bark contains salicin, a plant salicylate. It might have an additive effect when taken with other salicylate-containing drugs such as 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 about Robaxisal: it already contains aspirin (paired with the muscle relaxant methocarbamol). Willow bark contains salicin, which your body turns into salicylic acid, basically a natural cousin of aspirin. So stacking the two means you're essentially doubling up on aspirin-like compounds, and the effects can add together.

In real life, that mostly raises your risk of aspirin's usual downsides: stomach upset or irritation, easier bruising or bleeding, and ringing in the ears at higher amounts. To be clear, this is a theoretical concern based on how these work, not something proven in studies, so don't panic. Still, I'd run it by your pharmacist or doctor before combining them, especially if you have any bleeding or ulcer history.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Schmid B, Kotter I, Heide L. Pharmacokinetics of salicin after oral administration of a standardised willow bark extract. Eur J Clin Pharmacol. 2001;57:387-91. 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 Aspirin, Methocarbamol one above is among them. If you take anything else, check it against the full list below.

Moderate 126 No known interaction 2,704 (incl. Aspirin, Methocarbamol)
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 Aspirin, Methocarbamol

This page covers Willow Bark only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Aspirin, Methocarbamol page lists 243 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Asarabacca (major), Beer (major), Danshen (major) and Piracetam (major).

By severity: 8 major · 207 moderate · 28 minor.

From our pharmacist’s overview on the Aspirin, Methocarbamol page

“Robaxisal combines aspirin with methocarbamol, a muscle relaxant, and the aspirin half is why this list warrants real attention rather than a shrug. Of the 243 supplement ingredients on file, the overwhelming majority (more than 200) can add to aspirin's blood-thinning effect and raise the risk of bleeding.”

Reviewed by 2 · Jul 18, 2026

Open the Aspirin, Methocarbamol 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 Aspirin, Methocarbamol 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 Aspirin, Methocarbamol 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

#1,173 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Aspirin, Methocarbamol
Top 10%

#157 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
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 Aspirin, Methocarbamol, 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 Aspirin, Methocarbamol supplement interactions › Every supplement checked against Aspirin, Methocarbamol, ranked by severity 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 Aspirin, Methocarbamol Together: Common Questions

Can you take Willow Bark with Aspirin, Methocarbamol?
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.
Why are there 2 interactions listed for Willow Bark and Aspirin, Methocarbamol?
Aspirin, Methocarbamol belongs to more than one drug category, and Willow Bark interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Willow Bark and Aspirin, Methocarbamol 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

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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.