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Dietary supplement

Willow Bark Extract Ingredients & Drug Interactions

by NOW

Willow Bark Extract label
See full label image
Capsule Category: Botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 23, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Willow Bark Extract against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

Willow Bark Extract is a dietary supplement by NOW with 1 active ingredient. Its ingredients are commonly taken for low back pain, osteoarthritis joint pain, headache.Based on those ingredients, 127 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Willow bark extract. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Willow Bark Extract by NOW

Ask about any prescription or over-the-counter medication and we check it for interactions with Willow Bark Extract by NOW — and tell you which ingredient is responsible.

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Computed from our clinical databases

HelloPharmacist Scorecard of Willow Bark Extract by NOW

Four independent checks of what is known — a summary of the available information, not a grade of the product itself.

Evidence for Intended Use
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not assessable

The stated purpose hasn't been mapped to our evidence data yet.

Why this rating?
  • We haven't mapped this product's purpose to our evidence data yet — it'll be graded on the next content refresh.
Ingredient Transparency
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.
Known Interaction Concern
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Willow Bark.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs.
  • For scale: 127 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.
Safety Information
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

HelloPharmacist summaryFully disclosed formula with no assessable stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Jul 25, 2024.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Willow Bark Extract, straight from the product label.

Brand NOW
Barcode (UPC) 733739047755
Net contents 100 Veg Capsule(s)
Market status On market
Date entered into DSLD Jul 25, 2024
DSLD ID 314221
Product type Botanical
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Vegan, Vegetarian, Adult (18 - 50 Years), Kosher, Women (not pregnant or lactating), Gluten Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Willow Bark Extract by NOW, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
2 Veg Capsule(s)
Maximum serving Sizes:
2 Veg Capsule(s)
Servings per container
50
UPC/BARCODE
733739047755
IngredientAmount% DV
Total Carbohydrates1 Gram(s)1%
Willow bark extract800 mg--

Other ingredients: Hypromellose, Stearic Acid

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Suggested/Recommended/Usage/Directions

Suggested Usage: Take 2 capsules 1 to 2 times daily as needed with food.

Formula

Willow is a shrub with a long history of traditional use. Modern scientific researchers have identified numerous compounds from its bark that contribute to its bioactivity. Of these active compounds, salicin is best known for its support of the body's healthy response to normal physiological stress. In addition to salicin, polyphenols and flavonoids have also been found to contribute to its activity. NOW Willow Bark has 15% salicin plus a natural balance of other bioactive compounds that may gently help to temporarily relieve minor pain caused from overexertion and typical everyday stress.

Willow Bark extract 400 mg-15% Salicin standardized extract

Triangle K (Kosher)

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Precautions

Caution: For adults only.

Not for pregnant or nursing women. Consult physician if taking medications (especially those that may affect bleeding), have a medical condition (including bleeding disorders or ulcers), or are planning to have surgery.

Do not take this product if allergic to aspirin.

Keep out of reach of children.

Not manufactured with yeast, wheat, gluten, soy, milk, egg, fish, shellfish or tree nut ingredients. Produced in a GMP facility that process other ingredients containing these allergens.

Seals/Symbols

GMP Quality Assured

Triangle K (Kosher)

Formulation

Temporary Relief from Minor Pain of Overexertion

Non GMO

Vegetarian/vegan

Made in Canada with globally sourced ingredients.

Not manufactured with yeast, wheat, gluten, soy, milk, egg, fish, shellfish or tree nut ingredients.

Natural color variation may occur in this product.

FDA Statement of Identity

A Dietary Supplement

General Statements

Botanicals/Herbs Family owned since 1968.

Storage

Store in a cool, dry place after opening.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Willow Bark Extract by NOW label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Willow Bark Extract label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Willow Bark Extract by NOW

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size2 Veg Capsule(s) Dosage formCapsule Servings per container50 Amounts shown are per serving.

Willow bark extract

Interacts with
127 drugs
800 mg per serving Form: Salicin

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...

Willow bark extract monograph & interactions

Other (inactive) ingredients: Hypromellose, Stearic Acid. These complete the product’s ingredient list but are not active constituents.

Interaction report

Willow Bark Extract by NOW Drug Interactions

Willow Bark Extract contains a single active ingredient, and it has known interactions with 127 medications. Here’s the picture, then you can look up your own drug.

Want to check YOUR meds against Willow Bark Extract?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
127Drugs
127 Moderate

Ingredients driving the most interactions

Willow bark extract 127

Individual Drug Interactions

The ingredients in Willow Bark Extract interact with 127 drugs. Click any drug to see the details.

1 of the 1 ingredient in Willow Bark Extract interact with drugs. Each result below shows which ingredient is responsible. Willow bark extract

Each ingredient & the kinds of drugs it affects

For each ingredient in Willow Bark Extract with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Willow bark extract5 drug types · 127 drugs

Acetazolamide

Theoretically, willow bark might result in additive adverse effects associated with acetazolamide.
Willow bark contains salicin, a plant salicylate. Human case reports suggests that a combination of acetazolamide and salicylate increases unbound plasma levels of acetazolamide, as well as adverse effects related to acetazolamide.

Likelihood Possible Evidence D
Anticoagulant/Antiplatelet Drugs

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.

Likelihood Probable Evidence D
Aspirin

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.

Likelihood Probable Evidence D
Choline Magnesium Trisalicylate (Trilisate)

Theoretically, willow bark might increase the effects and adverse effects of choline magnesium trisalicylate.
Willow bark contains salicin, a plant salicylate. It might have an additive effect when taken with other salicylate-containing drugs such as choline magnesium trisalicylate.

Likelihood Probable Evidence D
Salsalate (Disalcid)

Theoretically, willow bark might increase the effects and adverse effects of salsalate.
Willow bark contains salicin, a plant salicylate. It might have an additive effect when taken with other salicylate-containing drugs such as salsalate.

Likelihood Probable Evidence D
Willow bark extract full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Willow Bark Extract, from the product label.

NOW

See all NOW products
Name
NOW FOODS
Street Address
395 S. Glen Ellyn Rd.
City
Bloomingdale
State
IL
ZipCode
60108
Web Address
nowfoods.com
Pharmacist Counseling Corner

Willow Bark Extract by NOW: Common Questions

Does Willow Bark Extract by NOW interact with any medications?
Yes. Based on its ingredients, Willow Bark Extract has a known interaction with 127 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Willow Bark Extract contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.

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

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Ask a pharmacist

Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Willow Bark Extract label
Go deeper

The Full Monographs Behind Willow Bark Extract’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Willow Bark

Interacts with 127 drugs

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...

Read the full Willow Bark monograph →
Sources

Sources & How We Checked

Willow Bark Extract's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

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

The 12 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Willow Bark 12 references
  1. Chrubasik S, Eisenberg E, Balan E, et al. Treatment of low back pain exacerbations with willow bark extract: a randomized double-blind study. Am J Med 2000;109:9-14. PubMed
  2. Schmid B, Ludtke R, Selbmann HK, et al. Efficacy and tolerability of a standardized willow bark extract in patients with osteoarthritis: randomized placebo-controlled, double blind clinical trial. Phytother Res 2001;15:344-50. PubMed
  3. Biegert C, Wagner I, Ludtke R, et al. Efficacy and safety of willow bark extract in the treatment of osteoarthritis and rheumatoid arthritis: results of 2 randomized double-blind controlled trials. J Rheumatol 2004;31:2121-30.
  4. Unsworth J, d'Assis-Fonseca A, Beswick DT, Blake DR. Serum salicylate levels in a breast fed infant. Ann Rheum Dis 1987;46:638-9. PubMed
  5. Clark JH, Wilson WG. A 16-day-old breast-fed infant with metabolic acidosis caused by salicylate. Clin Pediatr (Phila) 1981;20:53-4. PubMed
  6. Chrubasik S, Kunzel O, Model A, et al. Treatment of low back pain with a herbal or synthetic anti-rheumatic: a randomized controlled study. Willow bark extract for low back pain. Rheumatology (Oxford) 2001;40:1388-93. PubMed
  7. 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
  8. Krivoy N, Pavlotzky E, Chrubasik S, et al. Effect of salicis cortex extract on human platelet aggregation. Planta Med 2001;67:209-12. PubMed
  9. Mills SY, Jacoby RK, Chacksfield M, Willoughby M. Effect of a proprietary herbal medicine on the relief of chronic arthritic pain: a double-blind study. Br J Rheumatol 1996;35:874-8. PubMed
  10. Chrubasik, S., Kunzel, O., Black, A., Conradt, C., and Kerschbaumer, F. Potential economic impact of using a proprietary willow bark extract in outpatient treatment of low back pain: an open non-randomized study. Phytomedicine 2001;8(4):241-251. PubMed
  11. <p>Moro PA, Flacco V, Cassetti F, Clementi V, Colombo ML, Chiesa GM, Menniti-Ippolito F, Raschetti R, Santuccio C. Hypovolemic shock due to severe gastrointestinal bleeding in a child taking an herbal syrup. Ann Ist Super Sanita. 2011;47(3):278-83.</p>
  12. Sweeney, K. R., Chapron, D. J., Brandt, J. L., Gomolin, I. H., Feig, P. U., and Kramer, P. A. Toxic interaction between acetazolamide and salicylate: case reports and a pharmacokinetic explanation. Clin Pharmacol Ther 1986;40(5):518-524.

See these in context on the Willow Bark monograph →

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

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