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Dietary supplement

Japanese Knotweed Ingredients & Drug Interactions

by Samsara Herbs

Japanese Knotweed label
See full label image
Powder Category: Botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Japanese Knotweed 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

Japanese Knotweed is a dietary supplement by Samsara Herbs with 1 active ingredient. Its ingredients are commonly taken for source of resveratrol, heart and circulation support, inflammation.Based on those ingredients, 826 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Japanese Knotweed. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Japanese Knotweed by Samsara Herbs

Ask about any prescription or over-the-counter medication and we check it for interactions with Japanese Knotweed by Samsara Herbs — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Japanese Knotweed by Samsara Herbs

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Aug 6, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
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.

This powder contains one active ingredient: Japanese Knotweed (also called hu zhang). It's a plant traditionally used in Asian medicine, and the form here is the whole powder — no added fillers or inactive ingredients.

Does it work?

Couldn't assess
Evidence for Intended Use · database check
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

We hold no graded evidence for this product's ingredients for its stated purpose.

Why this rating?
  • The label markets this product for: support healthy immune response and energy levels.
  • Our graded evidence for these ingredients doesn't cover that particular purpose.

The evidence we hold doesn't establish how well Japanese Knotweed works for any of its traditional uses. Studies on hepatitis, rheumatoid arthritis, wound healing, gout, osteoarthritis, and unstable angina all show insufficient reliable evidence to rate.

If you're considering this for one of those conditions, talk with your doctor about what the research actually supports for your situation.

The evidence, ingredient by ingredient Hu Zhang

How safe is it?

Some data gaps
Safety Information · database check
Some gaps

Safety data exists for these ingredients, but with some important gaps.

Why this rating?
  • We hold adverse-effect (side-effect) data for 0 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.

Japanese Knotweed is used in traditional medicine, but human safety data for supplements are limited. Its emodin content may cause digestive upset.

The safety data advises against use during pregnancy and breastfeeding because there isn't enough information about how it affects the uterus, bowel, or nursing infants.

Side effects, ingredient by ingredient Hu Zhang

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
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 — Hu Zhang.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs.
  • For scale: 827 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.

Before you take this, double-check with your pharmacist if you're on blood thinners or antiplatelet drugs (Moderate risk of bleeding), any drug your liver metabolizes via CYP1A2, CYP2C19, CYP3A4, or CYP2E1 enzymes (Moderate risk of higher drug levels), estrogen replacement therapy or hormonal birth control (Moderate risk of reduced effectiveness), or carbamazepine (Tegretol) for seizures (Minor risk of higher levels).

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no assessable stated purpose. Moderate medication interactions have been identified, and some safety-information gaps remain.

Japanese Knotweed may slow how your liver processes many medications and could increase bleeding risk with blood thinners — both reasons to check with your doctor or pharmacist before starting it. The evidence for its effectiveness is unclear across its traditional uses.

If you're pregnant, planning to become pregnant, or breastfeeding, the safety data advises against it.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Jun 24, 2020.

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 Japanese Knotweed, straight from the product label.

Brand Samsara Herbs
Barcode (UPC) X0017C2U7H
Net contents 16 Ounce(s); 454 Gram(s); 1 Pound(s)
Market status On market
Date entered into DSLD Jun 24, 2020
DSLD ID 220680
Product type Botanical
Supplement form Powder
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years)
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 Japanese Knotweed by Samsara Herbs, 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:
2.5 Gram(s)
Maximum serving Sizes:
2.5 Gram(s)
Servings per container
181
UPC/BARCODE
X0017C2U7H
IngredientAmount% DV
Japanese Knotweed2500 mg--

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.
Formula

Japanese Knotweed (50% Resveratrol)

FDA Statement of Identity

Dietary Supplement

Seals/Symbols

GMP Good Manufacturing Practice USA Tested 3rd party USA tested

General Statements

About us At Samsara Herbs, we believe that all positive change in the world must first begin with positive change from within. We invite you to tap into your own infinite power through the use of our potent herbal extracts! We seek out only quality herbs from our trusted sources from around the world for use in our herbal extracts. Samsara Herbs, dedicated to empowering your life force!

Formulation

Standardized herbal extracts contain isolated herbal compounds, in guaranteed amounts. Often having the prevalent compound found in an herb, in a significantly higher concentration than found in nature.

Description A vigorous and hardy vine, Japanese Knotweed is reported to have a positive immune response as a result of its resveratrol content. It is believed to support healthy energy levels, regulate healthy immune response and promote healthy aging.

Suggested/Recommended/Usage/Directions

Our water soluble herbal extracts are best mixed in juice or a smoothie, although mixing in water is perfectly fine if you can tolerate the taste.

Suggested Use: Take 1 Scoop 1-3 times per day or as recommended by your health care professional.

Storage

Storage Cool dry place, out of direct sunlight.

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: If you have a medical condition, are pregnant or taking medications, consult your hearth care professional before using this product.

Keep out of reach of children.

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

See for yourself

Japanese Knotweed by Samsara Herbs label

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

Japanese Knotweed 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 Japanese Knotweed by Samsara Herbs

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

Serving size2.5 Gram(s) Dosage formPowder Servings per container181 Amounts shown are per serving.

Japanese Knotweed

Interacts with
826 drugs
2500 mg per serving Form: Resveratrol

Hu Zhang (Japanese knotweed root) is a traditional Chinese herb that is one of the richest natural sources of resveratrol and emodin. Some lab and ear...

Japanese Knotweed monograph & interactions
Interaction report

Japanese Knotweed by Samsara Herbs Drug Interactions

Want to check YOUR meds against Japanese Knotweed?

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
826Drugs
826 Moderate

Ingredients driving the most interactions

Japanese Knotweed 826

Individual Drug Interactions

The ingredients in Japanese Knotweed interact with 826 drugs. Click any drug to see the details.

1 of the 1 ingredient in Japanese Knotweed interact with drugs. Each result below shows which ingredient is responsible. Japanese Knotweed

Each ingredient & the kinds of drugs it affects

For each ingredient in Japanese Knotweed 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.

Japanese Knotweed7 drug types · 826 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, hu zhang might increase the risk of bleeding when taken with anticoagulant or antiplatelet drugs.
Hu zhang contains the constituent resveratrol. Resveratrol seems to have antiplatelet effects.

Likelihood Possible Evidence D
Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, hu zhang might increase levels of drugs metabolized by CYP1A2.
Hu zhang contains the constituent resveratrol. In vitro research shows that resveratrol might inhibit the CYP1A2 enzyme. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2C19 (Cyp2C19) Substrates

Theoretically, hu zhang might increase levels of drugs metabolized by CYP2C19.
Hu zhang contains the constituent resveratrol. In vitro research shows that resveratrol might inhibit the CYP2C19 enzyme. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2E1 (Cyp2E1) Substrates

Theoretically, hu zhang might increase levels of drugs metabolized by CYP2E1.
Hu zhang contains the constituent resveratrol. In vitro research shows that resveratrol might inhibit the CYP2E1 enzyme. Also, a pharmacokinetic study shows that taking resveratrol 500 mg daily for 10 days prior to taking a single dose of chlorzoxazone 250 mg increases the maximum concentration of chlorzoxazone by about 54%, the area under the curve of chlorzoxazone by about 72%, and the half-life of chlorzoxazone by about 35%. Chlorzoxazone is used as a probe drug for CYP2E1.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, hu zhang might increase levels of drugs metabolized by CYP3A4.
Hu zhang contains the constituent resveratrol. In vitro research shows that resveratrol might inhibit the CYP3A4 enzyme. However, a clinical study in adults with NAFLD found that adding resveratrol 3000 mg daily for 8 weeks did not necessitate dose adjustments to any established medications metabolized by CYP3A4.

Likelihood Possible Evidence D
Estrogens

Theoretically, hu zhang might competitively inhibit the effects of estrogen replacement therapy.
In vitro research shows that hu zhang might have estrogenic activity.

Likelihood Possible Evidence D
Carbamazepine (Tegretol)

Theoretically, hu zhang might increase the effects and adverse effects of carbamazepine.
In animals, blood and tissue levels of carbamazepine were increased when given in combination with hu zhang. It is thought that increased levels of carbamazepine are due to cytochrome P450 3A4 (CYP3A4) inhibition. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Japanese Knotweed full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Japanese Knotweed, from the product label.

Samsara Herbs

See all Samsara Herbs products
Name
Aspen Copacking
Street Address
810 North 2800 West
City
Lindon
State
Utah
ZipCode
84042
Pharmacist Counseling Corner

Japanese Knotweed by Samsara Herbs: Common Questions

Does Japanese Knotweed by Samsara Herbs interact with any medications?
Yes. Based on its ingredients, Japanese Knotweed has a known interaction with 826 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Japanese Knotweed 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.
Can I take Japanese Knotweed if I'm pregnant or breastfeeding?
The safety data advises against it during both pregnancy and breastfeeding — there isn't enough information to know it's safe, and some of its compounds may affect the uterus or bowel. Talk with your doctor or midwife before considering it.
Does Japanese Knotweed actually work for arthritis or gout?
We don't have reliable evidence that it does. Studies on osteoarthritis, rheumatoid arthritis, and gout all show insufficient evidence to rate how well it works. If you're managing one of those conditions, ask your doctor what's proven to help.
What is emodin and why does it matter?
Emodin is a compound naturally present in Japanese Knotweed that may cause digestive upset — stomach discomfort, loose stools, or similar GI symptoms. If you have a sensitive stomach, this is worth keeping in mind.
If resveratrol slows my liver, does that mean it's dangerous?
Not necessarily dangerous, but it's important. A slower liver means some drugs can build up and potentially cause more side effects. That's why checking your exact medications with your pharmacist before starting is key.
Why does the data say 827 medications might interact with this?
Japanese Knotweed theoretically affects multiple liver enzyme systems — CYP1A2, CYP2C19, CYP3A4, and CYP2E1 — and many hundreds of medications are processed through those pathways. It doesn't mean you'll have a problem with all of them, but it's why we recommend checking your specific ones.

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

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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.

Japanese Knotweed label
Go deeper

The Full Monographs Behind Japanese Knotweed’s Ingredients

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

Herb & supplement monograph

Hu Zhang

Interacts with 826 drugs

Hu Zhang (Japanese knotweed root) is a traditional Chinese herb that is one of the richest natural sources of resveratrol and emodin. Some lab and early human research looks interesting for...

Read the full Hu Zhang monograph →
Sources

Sources & How We Checked

Japanese Knotweed'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 19 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.

Hu Zhang 19 references
  1. Pace-Asciak CR, Rounova O, Hahn SE, et al. Wines and grape juices as modulators of platelet aggregation in healthy human subjects. Clin Chim Acta 1996;246:163-82. PubMed
  2. Bertelli AA, Giovannini L, Bernini W, et al. Antiplatelet activity of cis-resveratrol. Drugs Exp Clin Res 1996;22:61-3.
  3. Pace-Asciak CR, Hahn S, Diamandis EP, et al. The red wine phenolics trans-resveratrol and quercetin block human platelet aggregation and eicosanoid synthesis: implications for protection against coronary heart disease. Clin Chim Acta 1995;235:207-19.
  4. Bertelli A, Bertelli AA, Gozzini A, Giovannini L. Plasma and tissue resveratrol concentrations and pharmacological activity. Drugs Exp Clin Res 1998;24:133-8.
  5. Bertelli AA, Giovannini L, Giannessi D, et al. Antiplatelet activity of synthetic and natural resveratrol in red wine. Int J Tissue React 1995;17:1-3.
  6. Piver B, Berthou F, Dreano Y, Lucas D. Inhibition of CYP3A, CYP1A and CYP2E1 activities by resveratrol and other non volatile red wine components. Toxicol Lett 2001;125:83-91. PubMed
  7. Matsuda H, Shimoda H, Morikawa T, Yoshikawa M. Phytoestrogens from the roots of Polygonum cuspidatum (Polygonaceae): structure-requirement of hydroxyanthraquinones for estrogenic activity. Bioorg Med Chem Lett 2001;11:1839-42. PubMed
  8. Zhang CZ, Wang SX, Zhang Y, et al. In vitro estrogenic activities of Chinese medicinal plants traditionally used for the management of menopausal symptoms. J Ethnopharmacol 2005;98:295-300. PubMed
  9. Chang, T. K., Chen, J., and Lee, W. B. Differential inhibition and inactivation of human CYP1 enzymes by trans-resveratrol: evidence for mechanism-based inactivation of CYP1A2. J.Pharmacol.Exp.Ther. 2001;299(3):874-882.
  10. Dobrydneva, Y., Williams, R. L., and Blackmore, P. F. trans-Resveratrol inhibits calcium influx in thrombin-stimulated human platelets. Br.J.Pharmacol. 1999;128(1):149-157.
  11. Kirk, R. I., Deitch, J. A., Wu, J. M., and Lerea, K. M. Resveratrol decreases early signaling events in washed platelets but has little effect on platalet in whole food. Blood Cells Mol.Dis. 2000;26(2):144-150.
  12. Zbikowska, H. M. and Olas, B. Antioxidants with carcinostatic activity (resveratrol, vitamin E and selenium) in modulation of blood platelet adhesion. J Physiol Pharmacol. 2000;51(3):513-520.
  13. Olas, B., Wachowicz, B., Saluk-Juszczak, J., and Zielinski, T. Effect of resveratrol, a natural polyphenolic compound, on platelet activation induced by endotoxin or thrombin. Thromb.Res 8-15-2002;107(3-4):141-145. PubMed
  14. Yu, C., Shin, Y. G., Kosmeder, J. W., Pezzuto, J. M., and van Breemen, R. B. Liquid chromatography/tandem mass spectrometric determination of inhibition of human cytochrome P450 isozymes by resveratrol and resveratrol-3-sulfate. Rapid Commun.Mass Spectro PubMed
  15. Ma, Z. H. and Ma, Q. Y. Resveratrol: a medical drug for acute pancreatitis. World J Gastroenterol. 6-7-2005;11(21):3171-3174. PubMed
  16. Pendurthi, U. R., Williams, J. T., and Rao, L. V. Resveratrol, a polyphenolic compound found in wine, inhibits tissue factor expression in vascular cells : A possible mechanism for the cardiovascular benefits associated with moderate consumption of wine. PubMed
  17. Chachay VS, Macdonald GA, Martin JH, Whitehead JP, O'Moore-Sullivan TM, Lee P, Franklin M, Klein K, Taylor PJ, Ferguson M, Coombes JS, Thomas GP, Cowin GJ, Kirkpatrick CM, Prins JB, Hickman IJ. Resveratrol does not benefit patients with nonalcoholic fatty
  18. Bedada SK, Neerati P. Resveratrol Pretreatment Affects CYP2E1 Activity of Chlorzoxazone in Healthy Human Volunteers. Phytother Res. 2016;30(3):463-8. PubMed
  19. Chi YC, Lin SP, Hou YC. A new herb-drug interaction of Polygonum cuspidatum, a resveratrol-rich nutraceutical, with carbamazepine in rats. Toxicol Appl Pharmacol 2012;263(3):315-22. PubMed

See these in context on the Hu Zhang 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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